spore: profile
id: samarium-oxide
spore_version: 0.2
family: oxide-ceramics
name: Samarium(III) oxide
abbreviation: Sm2O3
role: neutron-absorber and optical-glass oxide, and a high-k dielectric studied for MOS devices
category: ceramics
type: oxides
summary: |
  Samarium(III) oxide (Sm2O3, CAS 12060-58-1) is a solid with a cubic crystal structure and a molecular weight of 348.7 g/mol per PubChem. PubChem gives a density of 8.347 g/cm3 at 25 °C. A Nanografi product page gives 8.43 g/cm3, and the melting point is printed as 2325 °C in a Thermo Fisher safety data sheet and as 2335 °C on the Nanografi page. Suppliers list the oxide for neutron absorbers in reactor control rods and for optical and infrared-absorbing glasses. An open-access 2019 modelling paper quotes a dielectric constant of up to 15 for amorphous films. No space flight, vacuum or radiation test on Sm2O3 was found in the sources read.
best_for: Dense rare-earth oxide for optical and infrared-absorbing glass and for neutron-absorber uses, as listed by suppliers
weakest_at: No space or radiation test data for Sm2O3, and melting-point and density values that differ between suppliers and PubChem
identity:
  formula: Sm2O3
  cas: 12060-58-1
  crystal_system: cubic
  source: saip-sm2o3-poster
  where: Abstract (XRD confirms a cubic structure). CAS 12060-58-1 and molecular formula O3Sm2 from PubChem CID 159425, Names and Identifiers
tags:
  environments: []
  stresses: []
  applications:
    - radiation-shielding
    - optics-and-cameras
    - electronics-and-chips
properties:
  - benchmark: density
    value: 8.347
    unit: g/cm3
    scope: material
    conditions:
      temperature: 25 °C
      form: Sm2O3 powder
    method: Database value, read from the PubChem record for CID 159425
    status: ground
    source: pubchem-sm2o3
    where: Chemical and Physical Properties, Experimental Properties, Density
  - benchmark: density
    value: 8.43
    unit: g/cm3
    scope: material
    conditions:
      form: Sm2O3 powder (micron powder product, 325 mesh, supplier listing)
    method: Value printed on a supplier product page (not a test method stated)
    status: ground
    note: Supplier value. It differs from the PubChem value of 8.347 g/cm3 and from the 8.347 printed in the Thermo Fisher SDS.
    source: nanografi-sm2o3-powder
    where: Product specification block, density field
  - benchmark: melting_point
    value: 2325
    unit: °C
    scope: material
    conditions:
      purity: 99.9 weight percent Sm2O3 (Thermo Fisher Cat. No. 36278)
    method: Value printed in a supplier safety data sheet, Section 9
    status: ground
    note: The PubChem record gives no melting point for Sm2O3, so this value comes from the supplier SDS.
    source: wsu-sm2o3-sds
    where: Section 9, Physical and chemical properties, Melting Point/Range row
  - benchmark: melting_point
    value: 2335
    unit: °C
    scope: material
    conditions:
      form: nanopowder and powder listings on the supplier page
    method: Value printed on a supplier product page
    status: ground
    note: Supplier value. It is 10 °C above the 2325 °C printed in the Thermo Fisher SDS.
    source: nanografi-sm2o3-powder
    where: Product specification block, melting point field
  - benchmark: boiling_point
    value: 4118
    unit: °C
    scope: material
    conditions:
      form: samarium oxide nanopowder listing
    method: Value printed on a supplier product page, in the same sentence as the 2335 °C melting point
    status: ground
    note: Supplier value for a nanopowder listing, not a PubChem or SDS value.
    source: nanografi-sm2o3-nano
    where: Product description, melting and boiling points sentence
  - benchmark: molecular_weight
    value: 348.7
    unit: g/mol
    scope: material
    conditions:
      basis: computed by PubChem from the molecular formula
    method: Computed property read from the PubChem record for CID 159425
    status: calculated
    source: pubchem-sm2o3
    where: Computed Properties, Molecular Weight
  - benchmark: lattice_parameter
    label: Lattice parameter a, cubic Sm2O3 (conference abstract)
    value: 10.94
    unit: Å
    scope: material
    conditions:
      crystal_system: cubic
      temperature: sample calcined at 500 and 700 °C (the abstract does not say which calcination temperature gives this lattice parameter)
    method: X-ray diffraction, as reported in the abstract of a 2025 conference contribution
    status: ground
    note: From a conference abstract, not a peer-reviewed paper.
    source: saip-sm2o3-poster
    where: Abstract, sentence beginning "The structural analysis through x-ray diffraction"
  - benchmark: band_gap
    label: Measured band gap, cubic Sm2O3 crystal
    value: 4.9
    unit: eV
    scope: material
    conditions:
      crystal_system: cubic
      basis: value quoted by the 2019 paper from earlier measurements (its references 41 and 42)
    method: Measured value quoted in Section 3.1.3 of the modelling paper
    status: ground
    note: Quoted value, not measured by the authors of the 2019 paper. The paper gives 4.7 eV for monoclinic and 5.1 eV for hexagonal Sm2O3 for comparison.
    source: olsson-cai-2019
    where: Section 3.1.3 Electronic Properties, first sentence on measured band gaps
  - benchmark: dielectric_constant
    label: Dielectric constant of amorphous Sm2O3 films, upper value quoted
    value: 15
    bound: upper
    unit: '-'
    scope: material
    conditions:
      phase: amorphous films
      basis: value quoted by the paper from three earlier film studies (its references 27 to 29)
    method: Literature value quoted in the Introduction of the modelling paper
    status: ground
    note: A quoted upper value for thin amorphous films. Film thickness and deposition method are not given in the text read.
    source: olsson-cai-2019
    where: Introduction, paragraph on high-k dielectric use (text "up to 15 for the amorphous films")
  - benchmark: bulk_modulus
    label: Bulk modulus, cubic Sm2O3, experimental range quoted
    value: 130
    value_high: 149
    bound: range
    unit: GPa
    scope: material
    conditions:
      crystal_system: cubic
      basis: experimental range quoted by the paper from its references 40, 35 and 90
    method: Experimental values quoted in Table 3 of the modelling paper
    status: ground
    source: olsson-cai-2019
    where: Table 3, Experimental row, Bulk modulus column
  - benchmark: bulk_modulus
    label: Bulk modulus, cubic Sm2O3, calculated
    value: 137.26
    unit: GPa
    scope: material
    conditions:
      crystal_system: cubic
      basis: ab initio calculation in the modelling paper, with an interatomic potential
    method: Calculated value from the modelling paper
    status: calculated
    source: olsson-cai-2019
    where: Table 3, Cubic row, B (GPa) column
  - benchmark: elastic_modulus
    label: Young's modulus, cubic Sm2O3, calculated
    value: 191.06
    unit: GPa
    scope: material
    conditions:
      crystal_system: cubic
      basis: calculated value in the modelling paper
    method: Calculated value from the modelling paper
    status: calculated
    source: olsson-cai-2019
    where: Table 3, Cubic row, E (GPa) column
  - benchmark: ld50_oral
    label: Acute oral LD50, Sm2O3, rat
    value: 5
    bound: lower
    unit: g/kg
    scope: material
    conditions:
      species: rat
      route: oral
    method: Value printed in a supplier safety data sheet, Section 11 (component information)
    status: ground
    note: The SDS prints the value as greater than 5 g/kg, so 5 is a lower bound. No dermal or inhalation figure is listed.
    source: wsu-sm2o3-sds
    where: Section 11, Component Information table, LD50 Oral column
corrosion:
  - environment: Moist air and water (storage and handling)
    headline: Sm2O3 is air sensitive and hygroscopic according to the Thermo Fisher SDS.
    effect: The SDS lists exposure to moist air or water as a condition to avoid and says to keep the powder dry in a tightly closed container. It gives no mass-gain figure, so the rate of moisture uptake is not known from this source.
    rating: moderate
    conditions:
      form: powder
      exposure: not quantified
    source: wsu-sm2o3-sds
    where: Section 10 (Stability, Conditions to Avoid) and Section 7 (Storage)
  - environment: Acids
    headline: Sm2O3 is described as soluble in acids and is listed as incompatible with acids.
    effect: The PubChem record quotes Hawley for insoluble in water and soluble in acids, and the SDS lists acids as incompatible. Neither source gives a dissolution rate or temperature, so the rating is qualitative.
    rating: moderate
    conditions:
      basis: qualitative solubility statement
      exposure: not tested in the sources read
    source: pubchem-sm2o3
    where: Experimental Properties, Physical Description (Hawley entry)
risks:
  hazards:
    - text: PubChem's GHS record gives the signal word Warning and lists H400 (very toxic to aquatic life) and H410 (very toxic to aquatic life with long lasting effects), each in 44.6% of company reports.
      ghs:
        - H400
        - H410
      source: pubchem-sm2o3
      where: Safety and Hazards, GHS Classification (ECHA C and L notifications summary)
    - text: PubChem also notes that this chemical does not meet GHS hazard criteria in 55.4% (129 of 233) of company reports, so the notifications disagree.
      ghs: []
      source: pubchem-sm2o3
      where: Safety and Hazards, GHS Classification, Note
    - text: The Thermo Fisher SDS says the product is not considered hazardous by the 2012 OSHA Hazard Communication Standard and has no label elements. It prints an oral LD50 greater than 5 g/kg in rat.
      ghs: []
      source: wsu-sm2o3-sds
      where: Section 2 (Hazard identification) and Section 11 (Component Information)
  failure_risks:
    - mode: Moisture pick-up by the hygroscopic powder
      trigger: Storage or handling in moist air or contact with water
      consequence: The SDS calls the powder air sensitive and hygroscopic and asks for dry, tightly closed storage. The SDS gives no mass-gain figure, so the effect on composition is not quantified.
      severity: moderate
      source: wsu-sm2o3-sds
      where: Section 10 (Stability; Conditions to Avoid)
    - mode: Reaction with acids
      trigger: Contact with acids, which the SDS lists as incompatible
      consequence: Sm2O3 is a basic oxide that PubChem describes as soluble in acids, so oxide is lost from a part or powder exposed to acid. No rate or temperature is printed.
      severity: moderate
      source: pubchem-sm2o3
      where: Experimental Properties, Physical Description (Hawley entry); SDS Section 7 incompatible materials
  side_effects: []
  handling:
    - text: Avoid contact with skin and eyes and do not breathe dust. Handle the product only in a closed system or with appropriate exhaust ventilation.
      source: wsu-sm2o3-sds
      where: Section 7 (Handling)
    - text: Keep in a dry, cool, well-ventilated place in a tightly closed container. Keep away from acids, strong oxidizing agents and carbon dioxide.
      source: wsu-sm2o3-sds
      where: Section 7 (Storage; Incompatible Materials)
  mitigations:
    - text: Wear chemical safety goggles or eyeglasses and gloves as the SDS directs, and use a particle filter where dust may be breathed.
      source: wsu-sm2o3-sds
      where: Section 8 (Eye/face protection, skin and body protection, respiratory protection)
uses:
  - application: radiation-shielding
    device: Neutron absorber in control rods for nuclear power reactors (supplier listing)
    example: Nanografi lists neutron absorber in control rods for nuclear power reactors among the important application areas of its samarium oxide powder. No test result for this use was read.
    source: nanografi-sm2o3-powder
    where: Product description, Applications list
  - application: optics-and-cameras
    device: Optical and infrared-absorbing glasses (supplier listing)
    example: Nanografi lists optical and infrared-absorbing glasses as an important application area of its samarium oxide powder.
    source: nanografi-sm2o3-powder
    where: Product description, Applications list
  - application: electronics-and-chips
    device: High-k gate dielectric in MOS devices (research)
    example: The 2019 modelling paper says the most promising electronic device applications for Sm2O3 are found in MOS and ReRAM devices and quotes a dielectric constant of up to 15 for amorphous films.
    source: olsson-cai-2019
    where: Introduction, first paragraphs on electronic device applications
supply:
  - subject: Samarium and rare earths (USGS 2025 mine production, rare-earth oxide equivalent, all rare earths, not samarium alone)
    abundance: Not read in a source opened for this profile.
    producers:
      - country: China
        share_percent: 69.2
        year: 2025
      - country: United States
        share_percent: 13.1
        year: 2025
      - country: Australia
        share_percent: 7.4
        year: 2025
      - country: Burma
        share_percent: 5.6
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (samarium is listed by name)
        listed: true
    price: 'USGS: samarium oxide, 99.5% minimum, average price 2.82 dollars per kg in 2025e'
    import_reliance: 'USGS: net import reliance for rare-earth compounds and metals was 67 percent of apparent consumption in 2025e'
    export_controls: 'USGS: in April 2025 China tightened export controls covering samarium alloys, compounds, metals and oxides.'
    recycling: 'USGS: limited quantities of rare earths were recovered from batteries, permanent magnets and fluorescent lamps. The chapter does not single out samarium oxide.'
    substitutes:
      - 'USGS: substitutes are available for many applications but generally are less effective.'
    source: usgs-mcs2026-rare-earths
    where: 'Salient Statistics (price, net import reliance); World Mine Production and Reserves, 2025 column (world total 390,000 t REO); Events, Trends, and Issues; Recycling; Substitutes. Shares are calculated by Space Mushroom from the printed tonnes and the rounded world total, and cover all rare earths, not samarium alone. Critical list: USGS 2025 List of Critical Minerals page.'
media: []
documents:
  - title: 'PubChem: Samarium(III) oxide (CID 159425), Experimental Properties, GHS classification, Computed Properties'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159425/JSON
    year: 2026
  - title: Thermo Fisher Scientific safety data sheet, Samarium(III) oxide, Cat. No. 36278 (revision 29 March 2024), hosted by Washington State University
    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: 'Nanografi: Samarium oxide (Sm2O3) powder product page'
    type: datasheet
    url: https://shop.nanografi.com/rare-earth-materials/rare-earth-oxide-powder/samarium-oxide-sm2o3-powder/
    year: 2026
  - title: 'Nanografi: Samarium oxide nanoparticles product page'
    type: datasheet
    url: https://shop.nanografi.com/nanoparticles/single-metal-oxide-nanoparticles/samarium-oxide-nanoparticles/
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Rare Earths'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths.pdf
    year: 2026
  - title: 'USGS: About the 2025 List of Critical Minerals'
    type: report
    url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
    year: 2025
  - title: Effect of Temperature on Structural and Optical Properties of Sm2O3 (SAIP 2025 conference contribution)
    type: paper
    url: https://events2.saip.org.za/event/1/contributions/463/contribution.pdf
    year: 2025
  - title: 'Olsson, Cai, Cottom, Jakobsen and Shluger: Structural, Elastic, Vibrational and Electronic Properties of Amorphous Sm2O3 from Ab Initio Calculations (Computational Materials Science, 2019; open access via UCL Discovery)'
    type: paper
    url: https://discovery.ucl.ac.uk/id/eprint/10084314/1/Revised%20Manuscript.pdf
    year: 2019
gaps:
  - No space flight, vacuum, radiation-test or thermal-vacuum result for Sm2O3 was found in any source read. The neutron-absorber and optical-glass uses are catalogue statements from suppliers.
  - No PubChem melting point exists for Sm2O3. The two supplier melting points (2325 °C in the SDS and 2335 °C on the Nanografi page) are both kept and not reconciled.
  - Density differs between PubChem (8.347 g/cm3 at 25 °C), the Nanografi page (8.43 g/cm3) and the Thermo Fisher SDS (specific gravity 8.347, which is the same number). Both values are kept.
  - Thermal expansion coefficient was not recorded. The 2019 modelling paper prints 8.11 × 10^-6 K^-1 (calculated) and 7.5 − 8.8 × 10^-6 K^-1 (experimental) in exponent form, so per the brief these are left out.
  - Band gap range across the Sm2O3 phases (4.70 to 5.10 eV in the modelling paper) and thin-film band gaps (3.15 to 4.0 eV) were not recorded as properties. Only the cubic value of 4.9 eV is kept.
  - The 43 dielectric constant of 1991 electron-beam films was seen only in a search summary and not read in a fetched page, so it is not used. The INIS record for the dielectric film study returned HTTP 402 and the RSC 2023 perspective returned HTTP 403, so neither was read.
  - Space group of cubic Sm2O3 was not read in a source opened for this profile.
  - Atomic weights for samarium and oxygen were not read in a source opened for this profile, so the recipe parts carry no atomic_weight. The molecular weight 348.7 g/mol is PubChem's.
  - Abundance of samarium in the Earth's crust was not read in a source opened for this profile.
  - The EU critical raw materials list was not checked for samarium.
  - USGS world production is given for all rare earths. No samarium-only production figure was read, so the producer shares are rare-earth shares.
  - The PubChem GHS record and the Thermo Fisher SDS disagree on hazard classification (aquatic toxicity warnings versus not hazardous under OSHA). Both are recorded.
  - Several property names are not in the canonical list (band_gap, lattice_parameter, molecular_weight, ld50_oral). They use short snake_case names as the brief allows.
sources:
  pubchem-sm2o3:
    title: 'PubChem compound record, Samarium(III) oxide (CID 159425): Experimental Properties, Computed Properties, GHS Classification, Physical Description'
    id: CID 159425; CAS 12060-58-1
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/159425/JSON
    year: 2026
    kind: database
    license: public domain (NCBI)
  wsu-sm2o3-sds:
    title: Thermo Fisher Scientific safety data sheet, Samarium(III) oxide, Cat. No. 36278, revision 29 March 2024 (hosted by Washington State University)
    id: Cat. No. 36278; 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 safety data sheet, linked not reproduced
  nanografi-sm2o3-powder:
    title: 'Nanografi: Samarium oxide (Sm2O3) powder product page'
    id: supplier product page
    url: https://shop.nanografi.com/rare-earth-materials/rare-earth-oxide-powder/samarium-oxide-sm2o3-powder/
    year: 2026
    kind: web
    license: supplier web page, linked not reproduced
  nanografi-sm2o3-nano:
    title: 'Nanografi: Samarium oxide nanoparticles product page'
    id: supplier product page
    url: https://shop.nanografi.com/nanoparticles/single-metal-oxide-nanoparticles/samarium-oxide-nanoparticles/
    year: 2026
    kind: web
    license: supplier web page, linked not reproduced
  usgs-mcs2026-rare-earths:
    title: Mineral Commodity Summaries 2026, Rare Earths
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-critical-2025:
    title: About the 2025 List of Critical Minerals (USGS, final list of 60 minerals)
    id: Final 2025 List of Critical Minerals
    url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
    year: 2025
    kind: web
    license: public domain (USGS)
  saip-sm2o3-poster:
    title: Effect of Temperature on Structural and Optical Properties of Sm2O3 (SAIP 2025 conference contribution)
    id: SAIP 2025, contribution 463
    url: https://events2.saip.org.za/event/1/contributions/463/contribution.pdf
    year: 2025
    kind: paper
    license: conference abstract, linked not reproduced
  olsson-cai-2019:
    title: Structural, Elastic, Vibrational and Electronic Properties of Amorphous Sm2O3 from Ab Initio Calculations (Olsson, Cai, Cottom, Jakobsen, Shluger)
    id: doi:10.1016/j.commatsci.2019.109119 (Computational Materials Science, 2019); UCL Discovery eprint 10084314
    url: https://discovery.ucl.ac.uk/id/eprint/10084314/1/Revised%20Manuscript.pdf
    year: 2019
    kind: paper
    license: open access via UCL Discovery (as listed)
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 13
  unreachable: 2
  caveats: 3
  note: Drafted by an AI assistant on 2026-11-01 from pages opened in this run. Values are from PubChem, a Thermo Fisher SDS, two Nanografi product pages, a 2025 conference abstract and a 2019 open-access modelling paper, with USGS for supply. Two supplier values disagree on melting point and density and both are kept.
story:
  recipe:
    line: Sm2O3 is samarium(III) oxide. Each formula unit combines two samarium atoms with three oxygen atoms, and PubChem gives the formula as O3Sm2 with a molecular weight of 348.7 g/mol.
    parts:
      - name: Samarium
        symbol: Sm
        role: The metal centre, held in the +3 state in Sm2O3.
      - name: Oxygen
        symbol: O
        role: Oxygen anions around each samarium. The 2019 modelling paper describes each Sm as six-coordinated in a distorted octahedron in the cubic crystal.
  risk_groups:
    - title: For people
      level: 1
      verdict: 'Hazard data conflict: PubChem and the SDS differ'
      lead: PubChem's GHS record lists aquatic toxicity warnings, while the Thermo Fisher SDS calls the product not hazardous under OSHA.
      points:
        - label: Aquatic
          line: PubChem's GHS record gives the signal word Warning with H400 and H410 in 44.6 percent of company reports each.
        - label: SDS
          line: The Thermo Fisher SDS prints an oral LD50 greater than 5 g/kg in rat and no GHS label elements.
        - label: Dust
          line: Avoid breathing dust and use exhaust ventilation, as the SDS directs.
    - title: Moisture and acids
      verdict: Keep dry and away from acids
      lead: The SDS calls the powder air sensitive and hygroscopic, and lists acids as incompatible.
      points:
        - label: Storage
          line: Keep the container tightly closed in a dry, cool, well-ventilated place.
        - label: Acids
          line: PubChem describes the oxide as soluble in acids, so acid contact removes material.
  why: Samarium(III) oxide is a dense, high-melting rare-earth oxide. Suppliers list it for neutron absorbers in reactor control rods and for optical and infrared-absorbing glasses. Samarium is also on the USGS 2025 critical mineral list, so its supply is closely watched.
  uses:
    - where: Neutron absorbers in reactor control rods (supplier listing)
      line: Nanografi lists neutron absorber in control rods for nuclear power reactors among the important application areas of its Sm2O3 powder. No test result for this use was read.
    - where: Optical and infrared-absorbing glasses
      line: Nanografi lists optical and infrared-absorbing glasses as a further application area of the same powder.
    - where: High-k dielectric research in MOS devices
      line: The 2019 modelling paper says the most promising electronic device applications for Sm2O3 are MOS and ReRAM devices, and quotes a dielectric constant of up to 15 for amorphous films.
  can_do:
    - label: Neutron absorber
      value: Reactor control rods (supplier listing)
      line: Nanografi lists neutron absorber in control rods for nuclear power reactors as an application of its Sm2O3 powder. No test result for this use was read.
    - label: Optical glass
      value: Optical and infrared-absorbing glasses (supplier listing)
      line: Nanografi lists optical and infrared-absorbing glasses as a further application of the same powder.
    - label: Melting point
      value: 2325 °C (SDS) and 2335 °C (Nanografi)
      line: The Thermo Fisher SDS prints a melting point of 2325 °C, and the Nanografi page prints 2335 °C for the same oxide.
  compare: Sm2O3 is a dense, high-melting oxide with a cubic crystal structure. PubChem gives 8.347 g/cm3 at 25 °C for its density, while the Nanografi page gives 8.43 g/cm3. Its melting point is printed as 2325 °C in the SDS and 2335 °C on the Nanografi page, and the modelling paper gives a calculated bulk modulus of 137.26 GPa for the cubic crystal. Its main space-relevant case is as a dielectric and optical material in research, with no flight record found.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Bulk modulus
      benchmark: bulk_modulus
  handling:
    - PubChem and the Thermo Fisher SDS both point to acid incompatibility. Keep the powder away from acids and strong oxidizing agents.
    - The SDS asks for dry, tightly closed storage because the powder is hygroscopic.
    - Avoid breathing dust, and handle in a closed system or with exhaust ventilation.
  good_for:
    - Optical and infrared-absorbing glass, as supplier listings describe.
    - Research on high-k dielectrics, where the 2019 modelling paper quotes a dielectric constant of up to 15 for amorphous films.
  watch_out:
    - Two supplier melting points (2325 °C and 2335 °C) and two densities (8.347 and 8.43 g/cm3) differ, so check the source that matches the grade and form you need.
    - PubChem's aquatic toxicity warnings and the SDS's not-hazardous classification disagree.
    - No space or radiation test on Sm2O3 was found, so treat the neutron-absorber and glass uses as supplier claims.
  verdict: 'Sm2O3 is a dense, high-melting rare-earth oxide with useful supplier-listed uses in neutron absorbers and optical glasses, and a research record as a high-k dielectric. For space work it is unproven: no flight or radiation test was found, and the melting point and density values differ between sources.'