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.
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
  source: pubchem-la2o3
  where: CID 150906 (lanthanum sesquioxide); each oxide has its own PubChem CID listed under identity.oxides
  oxides:
    - oxide: La2O3
      name: Lanthanum(III) oxide
      cas: 1312-81-8
      source: pubchem-la2o3
      where: Names and Identifiers, CAS (CID 150906)
    - oxide: Nd2O3
      name: Neodymium(III) oxide
      cas: 1313-97-9
      source: pubchem-nd2o3
      where: Names and Identifiers, CAS (CID 159373)
    - oxide: Gd2O3
      name: Gadolinium(III) oxide
      cas: 12064-62-9
      source: pubchem-gd2o3
      where: Names and Identifiers, CAS (CID 159427)
    - oxide: Er2O3
      name: Erbium(III) oxide
      cas: 12061-16-4
      source: pubchem-er2o3
      where: Names and Identifiers, CAS (CID 159426)
    - oxide: Eu2O3
      name: Europium(III) oxide
      cas: 1308-96-9
      source: pubchem-eu2o3
      where: Names and Identifiers, CAS (CID 159371)
    - oxide: Ho2O3
      name: Holmium(III) oxide
      cas: 12055-62-8
      source: pubchem-ho2o3
      where: Names and Identifiers, CAS (CID 159423)
    - oxide: Sm2O3
      name: Samarium(III) oxide
      cas: 12060-58-1
      source: pubchem-sm2o3
      where: Names and Identifiers, CAS (CID 159425)
    - oxide: Sc2O3
      name: Scandium oxide
      cas: 12060-08-1
      source: pubchem-sc2o3
      where: Names and Identifiers, CAS (CID 134661)
    - oxide: Tb4O7
      name: Terbium(III
      IV) oxide: null
      cas: 12037-01-3
      source: matltech-tb4o7
      where: Product specification table, CAS No. row
    - oxide: Tm2O3
      name: Thulium(III) oxide
      cas: 12036-44-1
      source: pubchem-tm2o3
      where: Names and Identifiers, CAS (CID 159411)
    - oxide: Yb2O3
      name: Ytterbium(III) oxide
      cas: 1314-37-0
      source: pubchem-yb2o3
      where: Names and Identifiers, CAS (CID 159375)
    - oxide: Lu2O3
      name: Lutetium(III) oxide
      source: chemicalbook-lu2o3
      where: CAS not read in a fetched source
tags:
  environments: []
  stresses: []
  applications:
    - optics-and-cameras
    - batteries
properties:
  - benchmark: density
    label: Density, lanthanum oxide (La2O3)
    value: 6.51
    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
  - benchmark: density
    label: Density, lanthanum oxide (La2O3), supplier SDS
    value: 6.51
    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
  - benchmark: density
    label: Density, neodymium oxide (Nd2O3)
    value: 7.24
    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
  - benchmark: density
    label: Density, gadolinium oxide (Gd2O3), PubChem
    value: 7.407
    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
  - benchmark: density
    label: Density, gadolinium oxide (Gd2O3), supplier SDS
    value: 7.07
    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
  - benchmark: density
    label: Density, erbium oxide (Er2O3)
    value: 8640
    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
  - benchmark: density
    label: Density, europium oxide (Eu2O3)
    value: 7.42
    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
  - benchmark: density
    label: Density, holmium oxide (Ho2O3)
    value: 8.41
    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
  - benchmark: density
    label: Density, samarium oxide (Sm2O3), PubChem
    value: 8.347
    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
  - benchmark: density
    label: Specific gravity, samarium oxide (Sm2O3), supplier SDS
    value: 8.347
    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
  - benchmark: density
    label: Density, scandium oxide (Sc2O3)
    value: 3.864
    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
  - benchmark: density
    label: Density, terbium(III,IV) oxide (Tb4O7)
    value: 7.3
    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
  - benchmark: density
    label: Density, thulium oxide (Tm2O3)
    value: 8.6
    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
  - benchmark: density
    label: Density, ytterbium oxide (Yb2O3)
    value: 9.2
    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
  - benchmark: density
    label: Density, lutetium oxide (Lu2O3), vendor
    value: 9.42
    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
  - benchmark: density
    label: Density, lutetium oxide (Lu2O3), research paper
    value: 9.5
    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)
  - benchmark: melting_point
    label: Melting point, lanthanum oxide (La2O3), PubChem
    value: 2304
    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
  - 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)
  - benchmark: melting_point
    label: Melting point, lanthanum oxide (La2O3), supplier SDS
    value: 2315
    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
  - benchmark: melting_point
    label: Melting point, neodymium oxide (Nd2O3)
    value: 2233
    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
  - benchmark: melting_point
    label: Melting point, gadolinium oxide (Gd2O3), PubChem
    value: 2339
    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
  - benchmark: melting_point
    label: Melting point, gadolinium oxide (Gd2O3), supplier SDS
    value: 2420
    unit: °C
    bound: lower
    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)
  - benchmark: melting_point
    label: Melting point, erbium oxide (Er2O3)
    value: 2418
    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
  - benchmark: melting_point
    label: Melting point, europium oxide (Eu2O3)
    value: 2350
    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
  - benchmark: melting_point
    label: Melting point, holmium oxide (Ho2O3)
    value: 2415
    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
  - benchmark: melting_point
    label: Melting point, samarium oxide (Sm2O3), supplier SDS
    value: 2325
    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
  - benchmark: melting_point
    label: Melting point, scandium oxide (Sc2O3)
    value: 2485
    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
  - benchmark: melting_point
    label: Melting point, terbium(III,IV) oxide (Tb4O7)
    value: 2340
    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
  - benchmark: melting_point
    label: Melting point, thulium oxide (Tm2O3)
    value: 2425
    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
  - benchmark: melting_point
    label: Melting point, ytterbium oxide (Yb2O3)
    value: 2435
    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
  - benchmark: melting_point
    label: Melting point, lutetium oxide (Lu2O3), vendor
    value: 2487
    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
  - benchmark: melting_point
    label: Melting point, lutetium oxide (Lu2O3), research paper
    value: 2510
    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))
  - benchmark: refractive_index
    label: Refractive index, lutetium oxide (Lu2O3)
    value: 1.93
    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
  - benchmark: specific_heat
    label: Specific heat, lutetium oxide (Lu2O3), crystal
    value: 0.26
    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
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.
      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).
      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
        mine_production: 270,000 t REO (2025, world total about 390,000 t)
        reserves: 44,000,000 t (2025)
      - country: Australia
        mine_production: 29,000 t REO (2025)
        reserves: 6,300,000 t
      - country: Burma
        mine_production: 22,000 t REO (2025)
        reserves: not available in the USGS table
      - country: United States
        mine_production: 51,000 t REO in mineral concentrates (2025 estimate)
        reserves: 1,900,000 t
    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.'
    import_reliance: 'US net import reliance, compounds and metals: 67 percent (2025 estimate); 53 percent in 2024.'
    export_controls: China added controls on samarium, gadolinium, terbium, dysprosium, lutetium, scandium and yttrium compounds and oxides in April 2025. In October 2025 it added europium, holmium, erbium, thulium and ytterbium, and in November it suspended the October controls for one year.
    price: 'USGS 2025 average prices in dollars per kg: lanthanum oxide 99.5 percent minimum 1.00; samarium oxide 99.5 percent minimum 2.82; europium oxide 99.99 percent minimum 27; gadolinium oxide 99.99 percent minimum 30; neodymium oxide 99.5 percent minimum 73.'
    source: usgs-mcs2026-rare-earths
    where: Salient Statistics; Import Sources; World Mine Production and Reserves table; Events, Trends, and Issues; Recycling; Substitutes
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).
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
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.'
story:
  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
      level: 1
      verdict: Irritant powder, or not hazardous by OSHA
      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.
    - 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.
  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
      value: 2233 to 2510 °C
      line: Melting points run from 2233 °C (Nd2O3, PubChem) to 2510 °C (Lu2O3, Tohoku).
    - label: High density
      value: 3.864 to 9.5 g/cm3
      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.
    - label: Optical index
      value: 1.93 at 532 nm (Lu2O3)
      line: The lutetia property list gives a refractive index of 1.93 at 532 nm. No index was read for the other oxides.
  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
    - label: Density
      benchmark: density
    - label: Refractive index
      benchmark: refractive_index
  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.