{
  "spore": "profile",
  "id": "rare-earth-oxides",
  "spore_version": "0.2",
  "family": "oxide-ceramics",
  "name": "Rare-earth sesquioxides (family)",
  "abbreviation": "Ln2O3",
  "role": "dense, high-melting trivalent oxide ceramics for optics and laser hosts",
  "category": "ceramics",
  "type": "oxides",
  "summary": "This family profile covers the trivalent rare-earth oxides of lanthanum, neodymium, gadolinium, erbium, europium, holmium, samarium, scandium, thulium, ytterbium and lutetium (Ln2O3), plus terbium(III,IV) oxide (Tb4O7). Yttrium oxide (profile yttrium-oxide) and cerium(IV) oxide (profile cerium-oxide) have their own profiles and are not repeated here. Melting points read from the sources run from 2233 °C for neodymia (PubChem) to 2510 °C for lutetia (a Tohoku paper). Densities run from 3.864 g/cm3 for scandia (PubChem) to 9.5 g/cm3 for lutetia (Tohoku). Where suppliers disagree, both figures are kept: gadolinia is 7.407 g/cm3 in PubChem but 7.07 in a supplier safety data sheet. Several oxides are hygroscopic or air sensitive, and suppliers ask for dry or inert-gas storage. Hazard data conflict: PubChem reports skin, eye and respiratory irritation for several oxides, while the lanthanum and samarium safety data sheets call the powder not hazardous under OSHA. No space-flight record was found for these oxides in this profile. The Tohoku paper proposes Nd-doped lutetia as a research scintillator and reports laser-ceramic studies of the same material.\n",
  "best_for": "Dense, high-melting oxide ceramics for optical and laser research; lutetia has the highest melting point and density in the sourced data (Tohoku paper, 2510 °C and 9.5 g/cm3)",
  "weakest_at": "Sourced data are thin for most members. Each oxide has about one PubChem density and melting value, several have no crystal-structure or thermal-conductivity figure, and no plasma or space record was read.",
  "identity": {
    "formula": "Ln2O3 (trivalent lanthanide sesquioxides); Tb4O7 for terbium",
    "designations": [],
    "source": "pubchem-la2o3",
    "where": "CID 150906 (lanthanum sesquioxide); each oxide has its own PubChem CID listed under identity.oxides"
  },
  "tags": {
    "environments": [],
    "stresses": [],
    "applications": [
      "optics-and-cameras",
      "batteries"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "label": "Density, lanthanum oxide (La2O3)",
      "value": 6.51,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "oxide": "La2O3",
        "temperature": "25 °C"
      },
      "method": "Experimental value in a chemical database (grade and method not stated)",
      "status": "ground",
      "source": "pubchem-la2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Density",
      "source_detail": {
        "title": "PubChem compound record, Lanthanum sesquioxide (CID 150906)",
        "id": "CID 150906, CAS 1312-81-8",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/150906/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, lanthanum oxide (La2O3), supplier SDS",
      "value": 6.51,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "oxide": "La2O3",
        "temperature": "25 °C"
      },
      "method": "Value printed in a supplier safety data sheet",
      "status": "ground",
      "source": "isoflex-la2o3-sds",
      "where": "Section 9, Density row",
      "source_detail": {
        "title": "Isoflex Lanthanum(III) oxide safety data sheet (Rev. 1)",
        "id": "CAS 1312-81-8",
        "url": "https://ww2.isoflex.com/cn/docman-all-categories/sds/542-lanthanum-oxide-rev-1/file",
        "year": 2026,
        "kind": "datasheet",
        "license": "supplier document, linked not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, neodymium oxide (Nd2O3)",
      "value": 7.24,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "oxide": "Nd2O3",
        "temperature": "25 °C"
      },
      "method": "Experimental value in a chemical database (grade and method not stated)",
      "status": "ground",
      "source": "pubchem-nd2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Density",
      "source_detail": {
        "title": "PubChem compound record, Neodymium sesquioxide (CID 159373)",
        "id": "CID 159373, CAS 1313-97-9",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159373/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, gadolinium oxide (Gd2O3), PubChem",
      "value": 7.407,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "oxide": "Gd2O3",
        "temperature": "15 °C"
      },
      "method": "Experimental value in a chemical database (printed as 7.407 at 15 °C)",
      "status": "ground",
      "source": "pubchem-gd2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Density",
      "source_detail": {
        "title": "PubChem compound record, Gadolinia (CID 159427)",
        "id": "CID 159427, CAS 12064-62-9",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159427/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, gadolinium oxide (Gd2O3), supplier SDS",
      "value": 7.07,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "oxide": "Gd2O3",
        "form": "powder"
      },
      "method": "Value printed in a supplier safety data sheet (temperature not printed)",
      "status": "ground",
      "note": "Lower than the PubChem value above. The SDS gives no temperature; the two values are kept side by side.",
      "source": "lorad-gd2o3-sds",
      "where": "Section 9, Forms Powder, Density row",
      "source_detail": {
        "title": "Lorad Chemical Gadolinium(III) oxide safety data sheet",
        "id": "CAS 12064-62-9",
        "url": "https://loradchemical.com/data/sds/SDS-Gadolinium-Oxide.pdf",
        "year": 2026,
        "kind": "datasheet",
        "license": "supplier document, linked not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, erbium oxide (Er2O3)",
      "value": 8640,
      "bound": "exact",
      "unit": "kg/m3",
      "scope": "material",
      "conditions": {
        "oxide": "Er2O3",
        "temperature": "not stated"
      },
      "method": "Value printed in a reference database; unit printed as kg m -3 and kept as printed",
      "status": "ground",
      "source": "webelements-er2o3",
      "where": "Compound data table, Density row",
      "source_detail": {
        "title": "WebElements, Dierbium trioxide (Er2O3)",
        "id": "CAS 12061-16-4",
        "url": "https://winter.group.shef.ac.uk/webelements/compounds/erbium/dierbium_trioxide.html",
        "year": 2026,
        "kind": "web",
        "license": "public (University of Sheffield)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, europium oxide (Eu2O3)",
      "value": 7.42,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "oxide": "Eu2O3",
        "temperature": "25 °C"
      },
      "method": "Experimental value in a chemical database (grade and method not stated)",
      "status": "ground",
      "source": "pubchem-eu2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Density",
      "source_detail": {
        "title": "PubChem compound record, Europium oxide (CID 159371)",
        "id": "CID 159371, CAS 1308-96-9",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159371/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, holmium oxide (Ho2O3)",
      "value": 8.41,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "oxide": "Ho2O3",
        "temperature": "25 °C"
      },
      "method": "Experimental value in a chemical database (grade and method not stated)",
      "status": "ground",
      "source": "pubchem-ho2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Density",
      "source_detail": {
        "title": "PubChem compound record, Holmium oxide (CID 159423)",
        "id": "CID 159423, CAS 12055-62-8",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159423/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, samarium oxide (Sm2O3), PubChem",
      "value": 8.347,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "oxide": "Sm2O3",
        "temperature": "25 °C"
      },
      "method": "Experimental value in a chemical database (grade and method not stated)",
      "status": "ground",
      "source": "pubchem-sm2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Density",
      "source_detail": {
        "title": "PubChem compound record, Samarium oxide (Sm2O3) (CID 159425)",
        "id": "CID 159425, CAS 12060-58-1",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159425/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "density",
      "label": "Specific gravity, samarium oxide (Sm2O3), supplier SDS",
      "value": 8.347,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "oxide": "Sm2O3",
        "purity": "99.9%"
      },
      "method": "Value printed as Specific Gravity in a supplier safety data sheet; the same value as the PubChem density",
      "status": "ground",
      "note": "Printed as specific gravity. Numerically the same as the PubChem density for this oxide. The SDS gives no temperature.",
      "source": "wsu-sm2o3-sds",
      "where": "Section 9, Specific Gravity row",
      "source_detail": {
        "title": "Samarium(III) oxide safety data sheet (Washington State University, revision 29 March 2024)",
        "id": "CAS 12060-58-1",
        "url": "https://wpcdn.web.wsu.edu/wp-research/uploads/sites/2909/2025/05/Samarium-III-Oxide-12060-58-1.pdf",
        "year": 2024,
        "kind": "datasheet",
        "license": "supplier document, linked not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, scandium oxide (Sc2O3)",
      "value": 3.864,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "oxide": "Sc2O3",
        "temperature": "25 °C"
      },
      "method": "Experimental value in a chemical database (grade and method not stated)",
      "status": "ground",
      "source": "pubchem-sc2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Density",
      "source_detail": {
        "title": "PubChem compound record, Scandium oxide (Sc2O3) (CID 134661)",
        "id": "CID 134661, CAS 12060-08-1",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/134661/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, terbium(III,IV) oxide (Tb4O7)",
      "value": 7.3,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "oxide": "Tb4O7",
        "purity": "99.9% or more",
        "form": "brown powder"
      },
      "method": "Value printed in a supplier product specification",
      "status": "ground",
      "source": "matltech-tb4o7",
      "where": "Product specification table, Density row",
      "source_detail": {
        "title": "Matltech, Terbium oxide (Tb4O7) product specification",
        "id": "CAS 12037-01-3",
        "url": "https://www.matltech.com/terbium-oxide-product/",
        "year": 2026,
        "kind": "web",
        "license": "supplier page, linked not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, thulium oxide (Tm2O3)",
      "value": 8.6,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "oxide": "Tm2O3",
        "temperature": "25 °C"
      },
      "method": "Experimental value in a chemical database (grade and method not stated)",
      "status": "ground",
      "source": "pubchem-tm2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Density",
      "source_detail": {
        "title": "PubChem compound record, Thulium oxide (Tm2O3) (CID 159411)",
        "id": "CID 159411, CAS 12036-44-1",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159411/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, ytterbium oxide (Yb2O3)",
      "value": 9.2,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "oxide": "Yb2O3",
        "temperature": "25 °C"
      },
      "method": "Experimental value in a chemical database (grade and method not stated)",
      "status": "ground",
      "source": "pubchem-yb2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Density",
      "source_detail": {
        "title": "PubChem compound record, Ytterbium oxide (CID 159375)",
        "id": "CID 159375, CAS 1314-37-0",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159375/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, lutetium oxide (Lu2O3), vendor",
      "value": 9.42,
      "bound": "exact",
      "unit": "g/mL",
      "scope": "material",
      "conditions": {
        "oxide": "Lu2O3",
        "temperature": "25 °C"
      },
      "method": "Literature value printed in a chemical vendor property list",
      "status": "ground",
      "source": "chemicalbook-lu2o3",
      "where": "Properties list, Density row",
      "source_detail": {
        "title": "ChemicalBook, Lutetium oxide property list",
        "id": "CB0399744",
        "url": "https://www.chemicalbook.com/ChemicalProductProperty_EN_CB0399744.htm",
        "year": 2026,
        "kind": "web",
        "license": "vendor aggregator page, linked not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, lutetium oxide (Lu2O3), research paper",
      "value": 9.5,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "oxide": "Lu2O3",
        "purity": "not stated"
      },
      "method": "Value stated in the introduction of a research paper on Nd-doped Lu2O3 ceramics",
      "status": "ground",
      "note": "Slightly higher than the vendor value of 9.42 above.",
      "source": "tohoku-nd-lu2o3",
      "where": "Introduction, first paragraph (the paper gives the figure as high density of 9.5 g/cm3)",
      "source_detail": {
        "title": "Scintillation Properties of Nd3+-Doped Lu2O3 Ceramics in the Visible and Near InfraRed Regions (Tohoku University)",
        "id": "SV9, Boulon",
        "url": "https://www.icc-imr.imr.tohoku.ac.jp/file/SV9_Boulon.pdf",
        "kind": "paper",
        "license": "author copy, linked not reproduced"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, lanthanum oxide (La2O3), PubChem",
      "value": 2304,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "La2O3"
      },
      "method": "Experimental value in a chemical database",
      "status": "ground",
      "source": "pubchem-la2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Melting Point",
      "source_detail": {
        "title": "PubChem compound record, Lanthanum sesquioxide (CID 150906)",
        "id": "CID 150906, CAS 1312-81-8",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/150906/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point range, lanthanum oxide (La2O3), supplier SDS",
      "value": 2305,
      "value_high": 2315,
      "bound": "range",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "La2O3",
        "pressure": "about 1013 hPa"
      },
      "method": "Range printed in a supplier safety data sheet",
      "status": "ground",
      "source": "isoflex-la2o3-sds",
      "where": "Section 9, Melting Point row (2305-2315 °C, 4181-4199 °F)",
      "source_detail": {
        "title": "Isoflex Lanthanum(III) oxide safety data sheet (Rev. 1)",
        "id": "CAS 1312-81-8",
        "url": "https://ww2.isoflex.com/cn/docman-all-categories/sds/542-lanthanum-oxide-rev-1/file",
        "year": 2026,
        "kind": "datasheet",
        "license": "supplier document, linked not reproduced"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, lanthanum oxide (La2O3), supplier SDS",
      "value": 2315,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "La2O3"
      },
      "method": "Value printed in a second supplier safety data sheet",
      "status": "ground",
      "source": "sputter-la2o3-msds",
      "where": "Physical properties block, Melting Point row",
      "source_detail": {
        "title": "Lanthanum oxide MSDS (sputtertargets.net)",
        "id": "lanthanum oxide MSDS",
        "url": "https://www.sputtertargets.net/Public/pdf/lanthanum-oxide-msds.pdf",
        "year": 2026,
        "kind": "datasheet",
        "license": "supplier document, linked not reproduced"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, neodymium oxide (Nd2O3)",
      "value": 2233,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "Nd2O3"
      },
      "method": "Experimental value in a chemical database",
      "status": "ground",
      "source": "pubchem-nd2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Melting Point",
      "source_detail": {
        "title": "PubChem compound record, Neodymium sesquioxide (CID 159373)",
        "id": "CID 159373, CAS 1313-97-9",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159373/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, gadolinium oxide (Gd2O3), PubChem",
      "value": 2339,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "Gd2O3"
      },
      "method": "Experimental value in a chemical database",
      "status": "ground",
      "source": "pubchem-gd2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Melting Point",
      "source_detail": {
        "title": "PubChem compound record, Gadolinia (CID 159427)",
        "id": "CID 159427, CAS 12064-62-9",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159427/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, gadolinium oxide (Gd2O3), supplier SDS",
      "value": 2420,
      "bound": "lower",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "Gd2O3",
        "form": "powder"
      },
      "method": "Value printed as greater than in a supplier safety data sheet",
      "status": "ground",
      "note": "The SDS gives a lower bound only. The PubChem value above is lower, so the two sources differ.",
      "source": "lorad-gd2o3-sds",
      "where": "Section 9, Melting Point row (> 2,420 ºC)",
      "source_detail": {
        "title": "Lorad Chemical Gadolinium(III) oxide safety data sheet",
        "id": "CAS 12064-62-9",
        "url": "https://loradchemical.com/data/sds/SDS-Gadolinium-Oxide.pdf",
        "year": 2026,
        "kind": "datasheet",
        "license": "supplier document, linked not reproduced"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, erbium oxide (Er2O3)",
      "value": 2418,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "Er2O3"
      },
      "method": "Value printed in a reference database",
      "status": "ground",
      "source": "webelements-er2o3",
      "where": "Compound data table, Melting point row",
      "source_detail": {
        "title": "WebElements, Dierbium trioxide (Er2O3)",
        "id": "CAS 12061-16-4",
        "url": "https://winter.group.shef.ac.uk/webelements/compounds/erbium/dierbium_trioxide.html",
        "year": 2026,
        "kind": "web",
        "license": "public (University of Sheffield)"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, europium oxide (Eu2O3)",
      "value": 2350,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "Eu2O3"
      },
      "method": "Experimental value in a chemical database",
      "status": "ground",
      "source": "pubchem-eu2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Melting Point",
      "source_detail": {
        "title": "PubChem compound record, Europium oxide (CID 159371)",
        "id": "CID 159371, CAS 1308-96-9",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159371/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, holmium oxide (Ho2O3)",
      "value": 2415,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "Ho2O3"
      },
      "method": "Experimental value in a chemical database",
      "status": "ground",
      "source": "pubchem-ho2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Melting Point",
      "source_detail": {
        "title": "PubChem compound record, Holmium oxide (CID 159423)",
        "id": "CID 159423, CAS 12055-62-8",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159423/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, samarium oxide (Sm2O3), supplier SDS",
      "value": 2325,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "Sm2O3",
        "purity": "99.9%"
      },
      "method": "Value printed in a supplier safety data sheet",
      "status": "ground",
      "note": "The PubChem record gives no melting point for samarium oxide, so this is the only melting value read for it in this profile.",
      "source": "wsu-sm2o3-sds",
      "where": "Section 9, Melting Point/Range row",
      "source_detail": {
        "title": "Samarium(III) oxide safety data sheet (Washington State University, revision 29 March 2024)",
        "id": "CAS 12060-58-1",
        "url": "https://wpcdn.web.wsu.edu/wp-research/uploads/sites/2909/2025/05/Samarium-III-Oxide-12060-58-1.pdf",
        "year": 2024,
        "kind": "datasheet",
        "license": "supplier document, linked not reproduced"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, scandium oxide (Sc2O3)",
      "value": 2485,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "Sc2O3"
      },
      "method": "Experimental value in a chemical database",
      "status": "ground",
      "source": "pubchem-sc2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Melting Point",
      "source_detail": {
        "title": "PubChem compound record, Scandium oxide (Sc2O3) (CID 134661)",
        "id": "CID 134661, CAS 12060-08-1",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/134661/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, terbium(III,IV) oxide (Tb4O7)",
      "value": 2340,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "Tb4O7",
        "purity": "99.9% or more"
      },
      "method": "Value printed in a supplier product specification",
      "status": "ground",
      "note": "The supplier gives a single value; a second source was not read in a fetched page to confirm it.",
      "source": "matltech-tb4o7",
      "where": "Product specification table, Melting Point row",
      "source_detail": {
        "title": "Matltech, Terbium oxide (Tb4O7) product specification",
        "id": "CAS 12037-01-3",
        "url": "https://www.matltech.com/terbium-oxide-product/",
        "year": 2026,
        "kind": "web",
        "license": "supplier page, linked not reproduced"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, thulium oxide (Tm2O3)",
      "value": 2425,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "Tm2O3"
      },
      "method": "Experimental value in a chemical database",
      "status": "ground",
      "source": "pubchem-tm2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Melting Point",
      "source_detail": {
        "title": "PubChem compound record, Thulium oxide (Tm2O3) (CID 159411)",
        "id": "CID 159411, CAS 12036-44-1",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159411/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, ytterbium oxide (Yb2O3)",
      "value": 2435,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "Yb2O3"
      },
      "method": "Experimental value in a chemical database",
      "status": "ground",
      "source": "pubchem-yb2o3",
      "where": "Chemical and Physical Properties, Experimental Properties, Melting Point",
      "source_detail": {
        "title": "PubChem compound record, Ytterbium oxide (CID 159375)",
        "id": "CID 159375, CAS 1314-37-0",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159375/JSON?heading=Experimental+Properties",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, lutetium oxide (Lu2O3), vendor",
      "value": 2487,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "Lu2O3"
      },
      "method": "Literature value printed in a chemical vendor property list",
      "status": "ground",
      "source": "chemicalbook-lu2o3",
      "where": "Properties list, Melting point row",
      "source_detail": {
        "title": "ChemicalBook, Lutetium oxide property list",
        "id": "CB0399744",
        "url": "https://www.chemicalbook.com/ChemicalProductProperty_EN_CB0399744.htm",
        "year": 2026,
        "kind": "web",
        "license": "vendor aggregator page, linked not reproduced"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, lutetium oxide (Lu2O3), research paper",
      "value": 2510,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "oxide": "Lu2O3"
      },
      "method": "Value stated in the introduction of a research paper on Nd-doped Lu2O3 ceramics",
      "status": "ground",
      "note": "Higher than the vendor value of 2487 above. The paper uses it to explain why single crystals are hard to grow.",
      "source": "tohoku-nd-lu2o3",
      "where": "Introduction, paragraph on crystal growth (high melting point (2,510 °C))",
      "source_detail": {
        "title": "Scintillation Properties of Nd3+-Doped Lu2O3 Ceramics in the Visible and Near InfraRed Regions (Tohoku University)",
        "id": "SV9, Boulon",
        "url": "https://www.icc-imr.imr.tohoku.ac.jp/file/SV9_Boulon.pdf",
        "kind": "paper",
        "license": "author copy, linked not reproduced"
      }
    },
    {
      "benchmark": "refractive_index",
      "label": "Refractive index, lutetium oxide (Lu2O3)",
      "value": 1.93,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "oxide": "Lu2O3",
        "wavelength": "532 nm"
      },
      "method": "Value printed in a chemical vendor property list",
      "status": "ground",
      "source": "chemicalbook-lu2o3",
      "where": "Properties list, refractive index row",
      "source_detail": {
        "title": "ChemicalBook, Lutetium oxide property list",
        "id": "CB0399744",
        "url": "https://www.chemicalbook.com/ChemicalProductProperty_EN_CB0399744.htm",
        "year": 2026,
        "kind": "web",
        "license": "vendor aggregator page, linked not reproduced"
      }
    },
    {
      "benchmark": "specific_heat",
      "label": "Specific heat, lutetium oxide (Lu2O3), crystal",
      "value": 0.26,
      "bound": "exact",
      "unit": "J/(g·K)",
      "scope": "material",
      "conditions": {
        "oxide": "Lu2O3",
        "temperature": "25 °C",
        "form": "crystal"
      },
      "method": "Value printed in a chemical vendor property list",
      "status": "ground",
      "source": "chemicalbook-lu2o3",
      "where": "Properties list, Specific Heat Capacity Cp(crystal) row",
      "source_detail": {
        "title": "ChemicalBook, Lutetium oxide property list",
        "id": "CB0399744",
        "url": "https://www.chemicalbook.com/ChemicalProductProperty_EN_CB0399744.htm",
        "year": 2026,
        "kind": "web",
        "license": "vendor aggregator page, linked not reproduced"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Air and moisture (storage and handling of the powders)",
      "headline": "Several rare-earth oxide powders are hygroscopic or air sensitive, so suppliers ask for dry, sealed or inert-gas storage.",
      "effect": "The lanthanum oxide SDS says to store under an inert atmosphere and protect from moisture, and lists moisture as a condition to avoid. The samarium oxide SDS calls the product air sensitive and hygroscopic. The gadolinium oxide SDS calls it hygroscopic and advises inert-gas storage. The lutetium oxide vendor page lists it as hygroscopic and sensitive, to be stored under inert gas.",
      "rating": "moderate",
      "conditions": {
        "form": "powders (no exposure time or humidity figure printed in any of the sources)",
        "exposure": "not quantified"
      },
      "source": "isoflex-la2o3-sds",
      "where": "Section 7 (Storage) and Section 10 (Conditions to Avoid: moisture)"
    },
    {
      "environment": "Air and moisture, samarium oxide",
      "headline": "The samarium oxide SDS lists the product as air sensitive and hygroscopic.",
      "effect": "The SDS gives no weight-gain figure, so the rate of moisture uptake is not known from this source.",
      "rating": "moderate",
      "conditions": {
        "form": "powder, 99.9% grade",
        "exposure": "not quantified"
      },
      "source": "wsu-sm2o3-sds",
      "where": "Section 10 (Stability and reactivity)"
    },
    {
      "environment": "Strong acids",
      "headline": "The gadolinium oxide SDS says the powder reacts with strong acids, and the samarium and lanthanum records say they dissolve in acids.",
      "effect": "Dissolution in acid is the expected behaviour for these basic oxides. The sources give no rate or temperature, so this is a qualitative rating, not a corrosion measurement.",
      "rating": "moderate",
      "conditions": {
        "basis": "qualitative statements in SDS and database records"
      },
      "source": "lorad-gd2o3-sds",
      "where": "Section 10 (Reactivity: Reacts with strong acids)"
    },
    {
      "environment": "Water",
      "headline": "The lanthanum oxide is practically insoluble in water.",
      "effect": "The lanthanum oxide SDS gives a water solubility of 0.00007 g/l at 20 °C. Several PubChem records also call the oxides insoluble in water and soluble in acids.",
      "rating": "low",
      "conditions": {
        "temperature": "20 °C"
      },
      "source": "isoflex-la2o3-sds",
      "where": "Section 9, Water Solubility row"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "PubChem's GHS record for lanthanum oxide gives skin irritation H315 (39.5 percent of reports), serious eye irritation H319 (40.1 percent) and respiratory irritation H335 (39.5 percent), with the signal word Warning.",
        "ghs": [
          "H315",
          "H319",
          "H335"
        ],
        "source": "pubchem-la2o3",
        "where": "Safety and Hazards, GHS Classification (CID 150906)"
      },
      {
        "text": "The lanthanum oxide SDS says the substance is not considered hazardous by the 2012 OSHA Hazard Communication Standard.",
        "ghs": [],
        "source": "isoflex-la2o3-sds",
        "where": "Section 2 (Classification)"
      },
      {
        "text": "PubChem's record for europium oxide gives H315, H319 and H335, each in 65.3 percent of reports, with the signal word Warning.",
        "ghs": [
          "H315",
          "H319",
          "H335"
        ],
        "source": "pubchem-eu2o3",
        "where": "Safety and Hazards, GHS Classification (CID 159371)"
      },
      {
        "text": "PubChem's record for thulium oxide gives H315, H319 and H335, each in 93.7 percent of reports.",
        "ghs": [
          "H315",
          "H319",
          "H335"
        ],
        "source": "pubchem-tm2o3",
        "where": "Safety and Hazards, GHS Classification (CID 159411)"
      },
      {
        "text": "PubChem's record for ytterbium oxide gives H315, H319 and H335, each in 34 percent of reports.",
        "ghs": [
          "H315",
          "H319",
          "H335"
        ],
        "source": "pubchem-yb2o3",
        "where": "Safety and Hazards, GHS Classification (CID 159375)"
      },
      {
        "text": "The gadolinium oxide SDS gives H319 (causes serious eye irritation) with the signal word Warning.",
        "ghs": [
          "H319"
        ],
        "source": "lorad-gd2o3-sds",
        "where": "Section 2 (Hazard Statements)"
      },
      {
        "text": "PubChem's record for gadolinium oxide gives H319 in 23.3 percent of reports, plus H400 and H410 in 40.5 percent of reports each (very toxic to aquatic life).",
        "ghs": [
          "H319",
          "H400",
          "H410"
        ],
        "source": "pubchem-gd2o3",
        "where": "Safety and Hazards, GHS Classification (CID 159427)"
      },
      {
        "text": "PubChem's record for erbium oxide gives H319 in 12.7 percent of reports and H400 and H410 in 37.3 percent of reports each.",
        "ghs": [
          "H319",
          "H400",
          "H410"
        ],
        "source": "pubchem-er2o3",
        "where": "Safety and Hazards, GHS Classification (CID 159426)"
      },
      {
        "text": "PubChem's record for samarium oxide gives H400 and H410 in 44.6 percent of reports each, and the samarium SDS calls the product not hazardous under the OSHA standard.",
        "ghs": [
          "H400",
          "H410"
        ],
        "source": "pubchem-sm2o3",
        "where": "Safety and Hazards, GHS Classification (CID 159425); also the samarium SDS, Section 2"
      },
      {
        "text": "PubChem's records for neodymium oxide, holmium oxide and scandium oxide say the substance does not meet GHS hazard criteria in most company reports (202 of 225, 116 of 116 and 31 of 33 respectively).",
        "ghs": [],
        "source": "pubchem-nd2o3",
        "where": "Safety and Hazards, GHS Classification (CID 159373); similar records for CID 159423 and CID 134661"
      }
    ],
    "failure_risks": [
      {
        "mode": "Moisture uptake and air sensitivity of the powder",
        "trigger": "Storage or handling of the powder in ordinary air",
        "consequence": "Suppliers call several powders hygroscopic or air sensitive and advise inert-gas storage. An open container can change the powder before use, so the composition check should be repeated before a melt or sinter.",
        "severity": "moderate",
        "source": "isoflex-la2o3-sds",
        "where": "Section 7 (Storage) and Section 10 (Conditions to Avoid: moisture)"
      },
      {
        "mode": "Reaction with strong acids",
        "trigger": "Contact with strong acids, for example in a cleaning or etching bath",
        "consequence": "The gadolinium oxide SDS says the powder reacts with strong acids, and the samarium oxide SDS lists acids as incompatible. A part or powder exposed to acid will lose oxide and may form soluble salts.",
        "severity": "moderate",
        "source": "lorad-gd2o3-sds",
        "where": "Section 10 (Reactivity; Incompatible Conditions)"
      },
      {
        "mode": "Density and melting point differ between sources",
        "trigger": "Using a single supplier or database value for design or purchase",
        "consequence": "For gadolinium oxide the density is 7.407 g/cm3 in PubChem and 7.07 g/cm3 in the supplier SDS. For lanthanum oxide the melting point is 2304 °C in PubChem and 2305 to 2315 °C in the supplier SDS. The spread is small, but it shows that a supplier certificate is needed for a specified part.",
        "severity": "low",
        "source": "lorad-gd2o3-sds",
        "where": "Section 9 (Density and Melting Point rows) against PubChem Experimental Properties"
      }
    ],
    "side_effects": [],
    "handling": [
      {
        "text": "Store the powder dry and sealed, under an inert atmosphere where the supplier asks for it. The lanthanum oxide SDS says store under an inert atmosphere and protect from moisture.",
        "source": "isoflex-la2o3-sds",
        "where": "Section 7 (Storage)"
      },
      {
        "text": "Avoid forming dust. Use appropriate exhaust ventilation where dust is formed, and wear safety glasses with side shields for eye protection.",
        "source": "lorad-gd2o3-sds",
        "where": "Section 7 (Handling), Section 8 (Exposure Controls)"
      },
      {
        "text": "Keep the powder away from acids, strong oxidizing agents and carbon dioxide. The samarium oxide SDS lists these as incompatible materials.",
        "source": "wsu-sm2o3-sds",
        "where": "Section 7 (Storage: Incompatible Materials)"
      }
    ],
    "mitigations": [
      {
        "text": "Handle the powder in accordance with good industrial hygiene and safety practice, as the samarium oxide SDS directs.",
        "source": "wsu-sm2o3-sds",
        "where": "Section 8 (Hygiene Measures)"
      }
    ]
  },
  "uses": [
    {
      "application": "optics-and-cameras",
      "device": "Nd-doped lutetium oxide transparent ceramic as an infrared scintillator (research candidate)",
      "example": "A Tohoku paper proposes Nd-doped Lu2O3 as an infrared scintillator candidate, because Lu2O3 has a density of 9.5 g/cm3 and a high atomic number, and suggests medical imaging as a use. The paper calls it a research proposal, not a product.",
      "source": "tohoku-nd-lu2o3",
      "where": "Introduction, first paragraph"
    },
    {
      "application": "optics-and-cameras",
      "device": "Solid-state laser host ceramic (research)",
      "example": "The same paper says Nd:Lu2O3 ceramics were studied for laser applications, and that solid-state reactions make a ceramic easier to make than a single crystal, because the melting point of 2510 °C makes single-crystal growth hard.",
      "source": "tohoku-nd-lu2o3",
      "where": "Introduction, paragraphs on laser applications and crystal growth"
    },
    {
      "application": "batteries",
      "device": "Rare-earth end uses across the family, not one oxide",
      "example": "USGS lists catalysts as the leading domestic end use of rare earths and magnets as the leading global use, with batteries, ceramics and glass, metallurgical applications and alloys, and polishing as other uses. The chapter does not give an oxide-by-oxide split.",
      "source": "usgs-mcs2026-rare-earths",
      "where": "Domestic Production and Use paragraph"
    }
  ],
  "supply": [
    {
      "subject": "Rare-earth oxides (rare-earth oxide equivalent, REO), US and world",
      "producers": [
        {
          "country": "China"
        },
        {
          "country": "Australia"
        },
        {
          "country": "Burma"
        },
        {
          "country": "United States"
        }
      ],
      "critical_lists": [
        {
          "list": "Not confirmed in this profile (the USGS critical-minerals page was not reachable)",
          "listed": false
        }
      ],
      "recycling": "USGS: limited quantities of rare earths were recovered from batteries, permanent magnets and fluorescent lamps.",
      "substitutes": [
        "USGS: substitutes are available for many applications but generally are less effective."
      ],
      "source": "usgs-mcs2026-rare-earths",
      "where": "Salient Statistics; Import Sources; World Mine Production and Reserves table; Events, Trends, and Issues; Recycling; Substitutes"
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "USGS Mineral Commodity Summaries 2026: Rare Earths (chapter)",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths.pdf",
      "year": 2026
    },
    {
      "title": "PubChem compound records for the rare-earth oxides (CIDs 150906, 159373, 159427, 159426, 159371, 159423, 159425, 134661, 159411, 159375)",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/150906",
      "year": 2026
    },
    {
      "title": "Isoflex lanthanum(III) oxide safety data sheet (Rev. 1)",
      "type": "sds",
      "url": "https://ww2.isoflex.com/cn/docman-all-categories/sds/542-lanthanum-oxide-rev-1/file",
      "year": 2026
    },
    {
      "title": "Lorad Chemical gadolinium(III) oxide safety data sheet",
      "type": "sds",
      "url": "https://loradchemical.com/data/sds/SDS-Gadolinium-Oxide.pdf",
      "year": 2026
    },
    {
      "title": "Washington State University samarium(III) oxide safety data sheet (revision 29 March 2024)",
      "type": "sds",
      "url": "https://wpcdn.web.wsu.edu/wp-research/uploads/sites/2909/2025/05/Samarium-III-Oxide-12060-58-1.pdf",
      "year": 2024
    },
    {
      "title": "Tohoku University, Scintillation Properties of Nd3+-Doped Lu2O3 Ceramics in the Visible and Near InfraRed Regions (SV9, Boulon)",
      "type": "paper",
      "url": "https://www.icc-imr.imr.tohoku.ac.jp/file/SV9_Boulon.pdf"
    }
  ],
  "gaps": [
    "Crystal structure is not read for most members. Only lutetium oxide is given (Sc2O3-type, space group Ia3, from a vendor page). The Wikipedia pages were not used for numbers.",
    "Thermal conductivity, thermal expansion and elastic modulus were not found in any fetched source for these oxides. The yttrium-oxide profile has these values for yttrium oxide only.",
    "Samarium oxide has no PubChem melting point. The only melting value is from the SDS (2325 °C); a second source was not read.",
    "Terbium oxide: a search summary said Tb4O7 decomposes rather than melting. That statement came from a search result and was not read in a fetched page, so the 2340 °C value is kept as printed by the supplier and flagged here.",
    "Erbium oxide has no density in PubChem. The density is from WebElements, which prints it in kg/m3 without a temperature.",
    "Lutetium oxide and terbium oxide have no PubChem experimental density or melting record (PubChem CIDs 4323797 and 16211492 print none); values come from vendor and research sources.",
    "Gadolinium oxide density is 7.407 g/cm3 in PubChem (at 15 °C) and 7.07 g/cm3 in the supplier SDS (no temperature). Both are kept; neither is preferred.",
    "Hazard data conflict for lanthanum oxide: PubChem reports irritation from some notifications, while the supplier SDS says not hazardous under OSHA. Both are kept.",
    "Plasma erosion and fluorine-plasma data for these oxides were not read in a paper. Patent text and search summaries mention erbium, scandium and gadolinium oxides in chamber coatings, but no measured comparison was read.",
    "No space-flight or outgassing record was found for any member in this profile.",
    "Abundance in the Earth's crust and atomic weights were not read, so the recipe carries no atomic_weight.",
    "The critical-minerals status of rare-earth oxides was not confirmed in this profile. The USGS critical-minerals page was not reachable, so critical_lists is marked as not confirmed.",
    "The USGS chapter says China's October 2025 export controls (including erbium, holmium, europium, thulium and ytterbium) were suspended for one year in November 2025. The current status was not checked beyond the chapter text.",
    "Refractive index is given for lutetium oxide only.",
    "Neodymium, holmium and scandium oxide records say the substance does not meet GHS hazard criteria in most reports, and the sample counts are small for scandium oxide (31 of 33 companies, and only 6.1 percent provided GHS data)."
  ],
  "story": {
    "why": "The rare-earth sesquioxides are dense, high-melting oxides. Their melting points run from 2233 °C (Nd2O3) to 2510 °C (Lu2O3 research paper), and their densities run from 3.864 g/cm3 (Sc2O3) to 9.5 g/cm3 (Lu2O3). The Tohoku paper and the lutetia vendor data point to optical ceramics and laser hosts. The sourced data are thin for most members, and the hazard and density values differ between sources.",
    "uses": [
      {
        "where": "Infrared scintillator research",
        "line": "A Tohoku paper proposes Nd-doped lutetium oxide as an infrared scintillator candidate, because its density is 9.5 g/cm3. It is a research proposal, not a product."
      },
      {
        "where": "Solid-state laser host research",
        "line": "The same paper says Nd:Lu2O3 ceramics were studied for lasers. Its melting point of 2510 °C makes single crystals hard to grow, so ceramics are made by solid-state reaction."
      },
      {
        "where": "Batteries, ceramics, glass and catalysts",
        "line": "USGS lists catalysts as the leading domestic use of rare earths and magnets as the leading global use. Batteries, ceramics and glass, and polishing are other uses. The chapter does not split these by oxide."
      }
    ],
    "can_do": [
      {
        "label": "High melting point",
        "line": "Melting points run from 2233 °C (Nd2O3, PubChem) to 2510 °C (Lu2O3, Tohoku).",
        "scope": "material",
        "value": "2233 to 2510 °C"
      },
      {
        "label": "High density",
        "line": "Densities run from 3.864 g/cm3 (Sc2O3, PubChem) to 9.5 g/cm3 (Lu2O3, Tohoku). Ytterbia is 9.2 g/cm3 in PubChem.",
        "scope": "material",
        "value": "3.864 to 9.5 g/cm3"
      },
      {
        "label": "Optical index",
        "line": "The lutetia property list gives a refractive index of 1.93 at 532 nm. No index was read for the other oxides.",
        "scope": "material",
        "value": "1.93 at 532 nm (Lu2O3)"
      }
    ],
    "compare": "The sourced values agree in order of magnitude. Scandia is the lightest, at 3.864 g/cm3, and the lanthana, neodymia and gadolinia values fall between 6.5 and 7.4 g/cm3 in PubChem. The heavy oxides, thulia, ytterbia and lutetia, run from 8.6 to 9.5 g/cm3. Gadolinia has two densities, 7.407 g/cm3 (PubChem) and 7.07 g/cm3 (supplier SDS), and the lanthana melting range is 2304 to 2315 °C across sources.",
    "compare_rows": [
      {
        "label": "Highest melting point",
        "benchmark": "melting_point",
        "scope": "material"
      },
      {
        "label": "Density",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Refractive index",
        "benchmark": "refractive_index",
        "scope": "material"
      }
    ],
    "handling": [
      "Store the powder dry and sealed, under inert gas where the supplier asks for it.",
      "Avoid dust. Use exhaust ventilation where dust is formed.",
      "Keep it apart from acids and strong oxidizing agents."
    ],
    "good_for": [
      "Dense optical ceramics. Lutetia has a density of 9.5 g/cm3 and a melting point of 2510 °C in the research paper, which makes single crystals hard to grow and favours ceramics.",
      "Research scintillators and laser hosts. The Tohoku paper proposes Nd-doped lutetia for both.",
      "High-temperature oxide parts that need a high melting point. The lowest melting point read is 2233 °C (Nd2O3, PubChem)."
    ],
    "watch_out": [
      "Moisture. Several powders are hygroscopic or air sensitive, so they need dry storage.",
      "Acid. The gadolinia SDS says the powder reacts with strong acids.",
      "Conflicting data. Gadolinia has two densities and lanthana has conflicting hazard classes, so a supplier certificate is needed.",
      "Thin data. Most oxides have one database value, and no space or plasma record was read."
    ],
    "verdict": "Lutetia and the heavy oxides have the strongest case for dense optical and laser ceramics, based on the Tohoku paper and vendor data. For most other members the sourced record is one database value and one or two supplier values, so each oxide needs its own check before use.",
    "recipe": {
      "line": "Ln2O3 is a metal oxide. Each formula unit has two trivalent rare-earth ions and three oxide ions. Terbium is sold as Tb4O7 (product specification, 99.9 percent or more). Scandium oxide is included in the same family.",
      "parts": [
        {
          "name": "Rare-earth metal (Ln)",
          "symbol": "Ln",
          "role": "The metal. Each oxide has one rare-earth element, from lanthanum (La) to lutetium (Lu), plus scandium (Sc)."
        },
        {
          "name": "Oxygen",
          "symbol": "O",
          "role": "Three oxide ions per formula unit balance the charge of the two trivalent ions."
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "PubChem reports irritation for several oxides, while the lanthanum and samarium SDSs call the powder not hazardous under OSHA. Both views are kept.",
        "points": [
          {
            "label": "The powder",
            "line": "PubChem reports skin, eye and respiratory irritation (H315, H319, H335) for lanthanum, europium, thulium and ytterbium oxides. The lanthanum and samarium SDSs say the product is not hazardous under the OSHA standard."
          },
          {
            "label": "Eye irritation",
            "line": "The gadolinium oxide SDS gives H319, serious eye irritation, with the signal word Warning. PubChem reports the same hazard in 23.3 percent of its gadolinium notifications."
          },
          {
            "label": "Aquatic life",
            "line": "PubChem's records for gadolinium, erbium and samarium oxides carry H400 and H410 (very toxic to aquatic life), in 37.3 to 44.6 percent of reports."
          }
        ],
        "level": 1,
        "verdict": "Irritant powder, or not hazardous by OSHA"
      },
      {
        "title": "If it fails",
        "lead": "These are data-sheet and database results, not service incidents.",
        "points": [
          {
            "label": "Moisture",
            "line": "Several powders are hygroscopic or air sensitive. The lanthanum oxide SDS says to protect it from moisture, and the samarium oxide SDS calls it air sensitive."
          },
          {
            "label": "Acid",
            "line": "The gadolinium oxide SDS says the powder reacts with strong acids. The samarium oxide SDS lists acids as incompatible."
          },
          {
            "label": "Spread between sources",
            "line": "The gadolinium oxide density is 7.407 g/cm3 in PubChem and 7.07 g/cm3 in the supplier SDS. A supplier certificate is needed for a specified part."
          }
        ]
      },
      {
        "title": "Handling and storage",
        "points": [
          {
            "label": "Keep it dry",
            "line": "Store the powder dry and sealed, under an inert atmosphere if the supplier asks for it."
          },
          {
            "label": "Avoid dust",
            "line": "Avoid forming dust, and use exhaust ventilation where dust is formed."
          },
          {
            "label": "Keep it apart",
            "line": "Keep the powders away from acids, strong oxidizing agents and carbon dioxide."
          }
        ]
      }
    ]
  },
  "updated": "2026-10-26",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 34,
    "unreachable": 1,
    "caveats": 5,
    "note": "Read by an AI assistant on 2026-10-26 from the PubChem records, USGS chapter, supplier SDS files, vendor and reference pages and one research paper fetched in that run. Values from search snippets were not used. The USGS critical-minerals page was not reachable. Caveats: density and melting values for several oxides come from one database record each; the gadolinia and lanthana sources disagree; terbia has one supplier value; the Tohoku paper is the only source for the lutetia research uses; hazard classifications conflict between PubChem and the supplier SDS for lanthana and samaria."
  },
  "sources": {
    "usgs-mcs2026-rare-earths": {
      "title": "Mineral Commodity Summaries 2026, Rare Earths (chapter)",
      "id": "USGS MCS 2026",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths.pdf",
      "year": 2026,
      "kind": "report",
      "license": "public domain (USGS)"
    },
    "pubchem-la2o3": {
      "title": "PubChem compound record, Lanthanum sesquioxide (CID 150906)",
      "id": "CID 150906, CAS 1312-81-8",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/150906/JSON?heading=Experimental+Properties",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "pubchem-nd2o3": {
      "title": "PubChem compound record, Neodymium sesquioxide (CID 159373)",
      "id": "CID 159373, CAS 1313-97-9",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159373/JSON?heading=Experimental+Properties",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "pubchem-gd2o3": {
      "title": "PubChem compound record, Gadolinia (CID 159427)",
      "id": "CID 159427, CAS 12064-62-9",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159427/JSON?heading=Experimental+Properties",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "pubchem-er2o3": {
      "title": "PubChem compound record, Erbium oxide (CID 159426)",
      "id": "CID 159426, CAS 12061-16-4",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159426/JSON?heading=Experimental+Properties",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "pubchem-eu2o3": {
      "title": "PubChem compound record, Europium oxide (CID 159371)",
      "id": "CID 159371, CAS 1308-96-9",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159371/JSON?heading=Experimental+Properties",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "pubchem-ho2o3": {
      "title": "PubChem compound record, Holmium oxide (CID 159423)",
      "id": "CID 159423, CAS 12055-62-8",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159423/JSON?heading=Experimental+Properties",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "pubchem-sm2o3": {
      "title": "PubChem compound record, Samarium oxide (Sm2O3) (CID 159425)",
      "id": "CID 159425, CAS 12060-58-1",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159425/JSON?heading=Experimental+Properties",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "pubchem-sc2o3": {
      "title": "PubChem compound record, Scandium oxide (Sc2O3) (CID 134661)",
      "id": "CID 134661, CAS 12060-08-1",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/134661/JSON?heading=Experimental+Properties",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "pubchem-tm2o3": {
      "title": "PubChem compound record, Thulium oxide (Tm2O3) (CID 159411)",
      "id": "CID 159411, CAS 12036-44-1",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159411/JSON?heading=Experimental+Properties",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "pubchem-yb2o3": {
      "title": "PubChem compound record, Ytterbium oxide (CID 159375)",
      "id": "CID 159375, CAS 1314-37-0",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159375/JSON?heading=Experimental+Properties",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "isoflex-la2o3-sds": {
      "title": "Isoflex Lanthanum(III) oxide safety data sheet (Rev. 1)",
      "id": "CAS 1312-81-8",
      "url": "https://ww2.isoflex.com/cn/docman-all-categories/sds/542-lanthanum-oxide-rev-1/file",
      "year": 2026,
      "kind": "datasheet",
      "license": "supplier document, linked not reproduced"
    },
    "sputter-la2o3-msds": {
      "title": "Lanthanum oxide MSDS (sputtertargets.net)",
      "id": "lanthanum oxide MSDS",
      "url": "https://www.sputtertargets.net/Public/pdf/lanthanum-oxide-msds.pdf",
      "year": 2026,
      "kind": "datasheet",
      "license": "supplier document, linked not reproduced"
    },
    "lorad-gd2o3-sds": {
      "title": "Lorad Chemical Gadolinium(III) oxide safety data sheet",
      "id": "CAS 12064-62-9",
      "url": "https://loradchemical.com/data/sds/SDS-Gadolinium-Oxide.pdf",
      "year": 2026,
      "kind": "datasheet",
      "license": "supplier document, linked not reproduced"
    },
    "wsu-sm2o3-sds": {
      "title": "Samarium(III) oxide safety data sheet (Washington State University, revision 29 March 2024)",
      "id": "CAS 12060-58-1",
      "url": "https://wpcdn.web.wsu.edu/wp-research/uploads/sites/2909/2025/05/Samarium-III-Oxide-12060-58-1.pdf",
      "year": 2024,
      "kind": "datasheet",
      "license": "supplier document, linked not reproduced"
    },
    "webelements-er2o3": {
      "title": "WebElements, Dierbium trioxide (Er2O3)",
      "id": "CAS 12061-16-4",
      "url": "https://winter.group.shef.ac.uk/webelements/compounds/erbium/dierbium_trioxide.html",
      "year": 2026,
      "kind": "web",
      "license": "public (University of Sheffield)"
    },
    "chemicalbook-lu2o3": {
      "title": "ChemicalBook, Lutetium oxide property list",
      "id": "CB0399744",
      "url": "https://www.chemicalbook.com/ChemicalProductProperty_EN_CB0399744.htm",
      "year": 2026,
      "kind": "web",
      "license": "vendor aggregator page, linked not reproduced"
    },
    "matltech-tb4o7": {
      "title": "Matltech, Terbium oxide (Tb4O7) product specification",
      "id": "CAS 12037-01-3",
      "url": "https://www.matltech.com/terbium-oxide-product/",
      "year": 2026,
      "kind": "web",
      "license": "supplier page, linked not reproduced"
    },
    "tohoku-nd-lu2o3": {
      "title": "Scintillation Properties of Nd3+-Doped Lu2O3 Ceramics in the Visible and Near InfraRed Regions (Tohoku University)",
      "id": "SV9, Boulon",
      "url": "https://www.icc-imr.imr.tohoku.ac.jp/file/SV9_Boulon.pdf",
      "kind": "paper",
      "license": "author copy, linked not reproduced"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/rare-earth-oxides/"
}