Strontium titanate SrTiO3

spore: profile
id: strontium-titanate
spore_version: 0.2
family: oxide-ceramics
name: Strontium titanate
abbreviation: SrTiO3
role: cubic perovskite oxide ceramic and single-crystal substrate
category: ceramics
type: oxides
summary: |
  Strontium titanate (SrTiO3) is a cubic perovskite oxide. A crystal datasheet for Verneuil-grown material gives its density as 5.12 g/cm3 and its melting point as 2353 K. Two product sheets give a melting point of 2060 °C for the powder. Its main commercial use is as a single-crystal substrate for growing oxide thin films and superconducting films.
best_for: Single-crystal substrates for growing oxide thin films, and thin-film tunable parts that work at low temperature
weakest_at: No strength, fracture or toughness value was found. The crystal datasheet gives only a Mohs hardness of 6 to 6.5
identity:
  formula: SrTiO3
  cas: 12060-59-2
  crystal_system: cubic
  space_group: Pm3m
  source: ereztech-spec
  where: Product Name, CAS Number and Molecular formula rows (Ereztech SR0592); cubic crystal system from the Crystal Structure row of azimp-crystal; space group Pm3m from the Wikipedia structure section (printed as Pm 3 m, No. 221)
tags:
  environments: []
  stresses: []
  applications:
    - electronics-and-chips
    - optics-and-cameras
properties:
  - benchmark: density
    label: Density, Verneuil-grown single crystal
    value: 5.12
    unit: g/cm3
    scope: material
    conditions:
      form: Verneuil-grown crystal, growth direction near [100]
      temperature: not stated on the datasheet
    method: Value printed in a crystal supplier datasheet
    status: ground
    source: azimp-crystal
    where: Physical Properties table, Density (g/cm3) row
  - benchmark: melting_point
    label: Melting point, Verneuil-grown single crystal
    value: 2353
    unit: K
    scope: material
    conditions:
      form: Verneuil-grown crystal
    method: Value printed in kelvin in a crystal supplier datasheet
    status: ground
    source: azimp-crystal
    where: Physical Properties table, Melting Point (K) row
  - benchmark: lattice_constant
    label: Lattice constant of the cubic cell, Verneuil-grown crystal
    value: 0.39045
    unit: nm
    scope: material
    conditions:
      form: Verneuil-grown crystal
      phase: cubic
    method: Value printed in a crystal supplier datasheet (non-canonical name, see gaps)
    status: ground
    source: azimp-crystal
    where: Crystallographic Properties table, Lattice Constant (nm) row, a = 0.39045
  - benchmark: hardness_mohs
    label: Mohs hardness, Verneuil-grown crystal
    value: 6
    value_high: 6.5
    bound: range
    unit: '-'
    scope: material
    conditions:
      form: Verneuil-grown crystal
    method: Range printed in a crystal supplier datasheet (non-canonical name, see gaps)
    status: ground
    source: azimp-crystal
    where: Physical Properties table, Hardness (Mohs) row, printed 6-6.5
  - benchmark: dielectric_constant
    label: Dielectric constant, Verneuil-grown crystal
    value: 300
    unit: '-'
    scope: material
    conditions:
      form: Verneuil-grown crystal
      frequency: not stated on the datasheet
      temperature: not stated on the datasheet
    method: Value printed in a crystal supplier datasheet with no unit
    status: ground
    source: azimp-crystal
    where: Physical Properties table, Dielectric Constant row
  - benchmark: density
    label: Density, single-crystal substrate (supplier product page)
    value: 5.11
    unit: g/cm3
    scope: material
    conditions:
      form: single-crystal substrate, Verneuil method
    method: Value on a supplier product page whose footnote says the product information is based on theoretical data, so it is recorded as calculated
    status: calculated
    source: sam-substrate
    where: Specification table, Density row; footnote under the table
  - benchmark: melting_point
    label: Melting point, single-crystal substrate (supplier product page)
    value: 2080
    unit: °C
    scope: material
    conditions:
      form: single-crystal substrate
    method: Value on a supplier product page whose footnote says the product information is based on theoretical data
    status: calculated
    source: sam-substrate
    where: Specification table, Melting Point row
  - benchmark: lattice_constant
    label: Lattice constant, single-crystal substrate (supplier product page)
    value: 3.905
    unit: Å
    scope: material
    conditions:
      phase: cubic perovskite
      form: single-crystal substrate
    method: Value on a supplier product page whose footnote says the product information is based on theoretical data
    status: calculated
    source: sam-substrate
    where: Specification table, Lattice Constant row, a = 3.905 Å
  - benchmark: dielectric_constant
    label: Dielectric constant, single-crystal substrate (supplier product page)
    value: 300
    unit: '-'
    scope: material
    conditions:
      temperature: room temperature
      frequency: 1 MHz
    method: Printed as approximately 300 on a supplier product page whose footnote says the product information is based on theoretical data
    status: calculated
    note: Printed with a tilde, so the value is approximate.
    source: sam-substrate
    where: Specification table, Dielectric Constants row, ~300 (R.T., 1 MHz)
  - benchmark: melting_point
    label: Melting point, solid (Stanford Advanced Materials safety data sheet)
    value: 2060
    unit: °C
    scope: material
    conditions:
      form: white to grey powder and pieces, CAS 12060-59-2
    method: Value printed in a supplier safety data sheet, version 2.0
    status: ground
    source: sam-msds
    where: Section III, Melting Point row
  - benchmark: melting_point
    label: Melting point, powder (Ereztech product specification)
    value: 2060
    unit: °C
    scope: material
    conditions:
      form: solid powder, product SR0592
    method: Value printed in a manufacturer's product specification (printed as 2060C)
    status: ground
    source: ereztech-spec
    where: Product specification, Melting point row
  - benchmark: assay_purity
    label: Assay (purity) of the powder, Ereztech SR0592
    value: 99
    unit: '%'
    scope: material
    conditions:
      method: purity by elemental analysis
      grade: printed as 99%+
    method: Value printed in a manufacturer's test specification (non-canonical name, see gaps)
    status: ground
    source: ereztech-spec
    where: Test specification, Assay (purity) row, printed 99%+
  - benchmark: dielectric_peak_temperature
    label: Diffuse permittivity peak on cooling, undoped sol-gel reference thin film
    value: 60
    unit: K
    scope: material
    conditions:
      form: undoped sol-gel thin film on platinized silicon (reference film, not bulk)
      frequency: 10 kHz (Figure 3 caption)
    method: Peak temperature read from the text describing the permittivity against temperature curve of the reference film (non-canonical name, see gaps)
    status: ground
    source: okhay2022
    where: Results, description of Figure 3a (reference ST thin film)
corrosion:
  - environment: Strong acids and strong bases
    headline: The safety data sheet lists strong acids and strong bases as incompatible. No corrosion test was found.
    effect: Stanford Advanced Materials lists strong acids and strong bases as incompatible materials for strontium titanate. The sheet gives no reaction product, rate or test result.
    rating: unknown
    conditions:
      basis: incompatibility list in a supplier safety data sheet
      form: powder
    source: sam-msds
    where: Section V (Incompatibility)
  - environment: Water
    headline: The powder is listed as insoluble in water. The sheet gives no humidity or ageing test.
    effect: The safety data sheet lists solubility in water as insoluble. No study of ageing or humidity exposure of strontium titanate was found in the sources read in this run.
    rating: unknown
    conditions:
      basis: solubility statement only
      form: powder
    source: sam-msds
    where: Section III (Solubility in water)
  - environment: Fire and high temperature
    headline: In a fire the material may emit toxic fumes. The sheet names strontium oxide and titanium oxide as decomposition products.
    effect: The safety data sheet says the material may emit toxic fumes in a fire and lists strontium oxide and titanium oxide as hazardous decomposition products. It gives no corrosion rate.
    rating: unknown
    conditions:
      basis: decomposition products listed in a supplier safety data sheet
      test: none
    source: sam-msds
    where: Section IV (Unusual fire and explosion hazards) and Section V (Hazardous decomposition)
risks:
  hazards:
    - text: The Stanford safety data sheet says strontium compounds have a low order of toxicity and that titanium compounds are considered physiologically inert. It also says the oxides and hydroxides of strontium are moderately caustic.
      ghs: []
      source: sam-msds
      where: Section VI (Health hazards)
    - text: The same sheet says the dust may be a nuisance dust that causes coughing and shortness of breath, and that it may cause irritation to the skin and eyes.
      ghs: []
      source: sam-msds
      where: Section VI (Acute inhalation, skin and eye)
  failure_risks:
    - mode: Higher dielectric loss in thin films than in single crystals
      trigger: Use as a thin film, where point defects, local polar regions and stresses are present
      consequence: The 2022 paper states that the dielectric loss of thin films is usually considerably higher than that of single crystals, and that it increases as the film gets thinner.
      severity: moderate
      source: okhay2022
      where: Introduction, first paragraph
    - mode: Reaction with strong acids or strong bases
      trigger: Contact with strong acids or strong bases
      consequence: The safety data sheet lists both as incompatible and gives no reaction product or rate.
      severity: low
      source: sam-msds
      where: Section V (Incompatibility)
  side_effects:
    - text: In a fire the safety data sheet says the material may emit toxic fumes, and that strontium oxide and titanium oxide form as decomposition products.
      affects: Firefighters and the surrounding area
      source: sam-msds
      where: Section IV (Fire) and Section V (Hazardous decomposition)
  handling:
    - text: Store in a tightly sealed container and wash thoroughly after handling, per the safety data sheet.
      source: sam-msds
      where: Section VII (Hazard label information)
    - text: For spills, use a HEPA filter vacuum, take care not to raise dust, and place the material in a closed container for disposal.
      source: sam-msds
      where: Section VII (Steps to be taken in case material is released)
    - text: The sheet recommends a NIOSH approved respirator, impervious gloves, safety glasses and clothing that prevents contact.
      source: sam-msds
      where: Section VIII (Protective equipment summary)
  mitigations:
    - text: Use local exhaust ventilation to keep exposure low, and recommended mechanical general ventilation, per the safety data sheet.
      source: sam-msds
      where: Section VIII (Ventilation)
uses:
  - application: electronics-and-chips
    device: Single-crystal substrate for epitaxial oxide thin films and superconducting films
    example: The Stanford Advanced Materials product page calls strontium titanate a popular crystal substrate for epitaxial growth of many oxide thin films, and says it is commonly used as a substrate for superconductor thin films.
    source: sam-substrate
    where: Product description text
  - application: electronics-and-chips
    device: Tunable thin-film microwave components
    example: The 2022 paper in Materials says that ferroelectric-related films are used in varactors, microwave filters, resonators and phase shifters, and that incipient ferroelectrics such as SrTiO3 are useful at cryogenic temperatures for tuning elements.
    source: okhay2022
    where: Introduction, first and second paragraphs
  - application: optics-and-cameras
    device: Special optical windows
    example: The Stanford Advanced Materials product page lists special optical windows and high-quality sputtering targets among its uses for the material.
    source: sam-substrate
    where: Product description text
supply:
  - subject: Strontium (mined as celestite)
    producers:
      - country: Iran
        share_percent: 55.6
        year: 2025
      - country: Spain
        share_percent: 22.2
        year: 2025
      - country: China
        share_percent: 17.8
        year: 2025
      - country: Mexico
        share_percent: 4.4
        year: 2025
    critical_lists: []
    recycling: 'USGS strontium chapter: Recycling: None.'
    substitutes:
      - 'USGS: barium can be substituted for strontium in ceramic ferrite magnets. No substitute is discussed for electronic perovskite ceramics.'
    source: usgs-mcs2026-strontium
    where: World Mine Production and Reserves table, 2025 column (gross weight of celestite in tons, per footnote 6; shares calculated by Space Mushroom against the printed world total of 450,000); Recycling; Substitutes
  - subject: Titanium (sponge metal, the USGS production table)
    producers:
      - country: China
        share_percent: 70.3
        year: 2025
      - country: Japan
        share_percent: 14.3
        year: 2025
      - country: Russia
        share_percent: 6.8
        year: 2025
      - country: Kazakhstan
        share_percent: 4.3
        year: 2025
    critical_lists: []
    recycling: 'USGS titanium chapter: consumption data for titanium scrap metal were withheld.'
    substitutes:
      - 'USGS: few materials possess titanium metal''s strength-to-weight ratio and corrosion resistance. The chapter does not discuss electronic perovskite ceramics.'
    source: usgs-mcs2026-titanium
    where: World Sponge Metal Production and Sponge and Pigment Capacity table, 2025 column (sponge metal, not titanium dioxide or mineral concentrates; shares calculated by Space Mushroom against the printed world total of 370,000); Recycling; Substitutes
documents:
  - title: 'Stanford Advanced Materials Material Safety Data Sheet: Strontium titanate, version 2.0 (revision date Sep 5, 2012), hosted by sputtertargets.net'
    type: sds
    url: https://www.sputtertargets.net/Public/pdf/strontium-titanate-msds.pdf
    year: 2012
  - title: 'Ereztech product specification SR0592: Strontium Titanium Oxide'
    type: datasheet
    url: https://ereztech.com/product/strontium-titanium-oxide-12060-59-2/?pdf=2446
  - title: 'Stanford Advanced Materials product page: Strontium titanate single-crystal substrate (catalog CY3345)'
    type: datasheet
    url: https://www.samaterials.com/strontium-titanate-single-crystal-substrate.html
  - title: 'Crystal datasheet: Strontium Titanate, Verneuil growth (azimp.ru PDF)'
    type: datasheet
    url: https://azimp.ru/upload/pdf-static/CRYSTAL/SrTiO3_Strontium_Titanate.pdf
  - title: 'Okhay, Vilarinho and Tkach: Low-Temperature Dielectric Response of Strontium Titanate Thin Films Manipulated by Zn Doping (Materials 15, 859)'
    type: paper
    url: https://ria.ua.pt/bitstream/10773/36031/1/Mat15%282022%290859-Okhay.pdf
    year: 2022
  - title: 'USGS Mineral Commodity Summaries 2026: Strontium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-strontium.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Titanium and Titanium Dioxide'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-titanium.pdf
    year: 2026
gaps:
  - No flight, vacuum, radiation, thermal-vacuum or space-environment result for strontium titanate was found in any source read in this run, so no environments tag is given.
  - No GHS hazard codes are recorded. The PubChem record could not be read (the site returned a browser check), and the Stanford safety data sheet prints no H-codes.
  - The Lorad Chemical product page could not be read by the fetch tools in this run, so its powder density and melting point are not recorded.
  - Atomic weights of strontium, titanium and oxygen were not read in a source this run, so the recipe parts carry no atomic_weight.
  - The molecular weight is printed without a unit in the Ereztech specification and in the Stanford safety data sheet, so it is left out.
  - Strontium abundance in the crust was not found in a source read in this run.
  - Strontium was variously included or not included on critical minerals lists, according to the USGS strontium chapter. No list status for this profile was confirmed, so critical_lists is empty. The titanium critical-list status was not checked.
  - The titanium figures are for titanium sponge metal. Titanium dioxide and mineral concentrate production were not read, so they are not recorded.
  - The thermal expansion and loss tangent values are printed with exponents in the crystal datasheet and the supplier product page, so they are left out.
  - 'Mohs hardness: Wikipedia gives a different value for synthetic material (''Mohs hardness 5.5 for synthetic, 6-6.5 for natural''). Wikipedia is used here only for composition and structure, so only the crystal datasheet''s 6 to 6.5 is recorded.'
  - The supplier product page's values are based on theoretical data, according to its footnote. They are recorded as calculated, and no measured value for the same quantity was found in the sources read here.
  - No humidity, ageing or long-term corrosion study for strontium titanate was found. The corrosion entries rest on the safety data sheet's incompatibility list and solubility statement.
  - Room-temperature permittivity of a sintered bulk ceramic was not found. The 2022 paper reports thin-film values, and its doped-film values are not recorded because they are for a different composition.
  - The non-canonical property names lattice_constant, hardness_mohs, assay_purity and dielectric_peak_temperature are used because the canonical list has no entry for them.
sources:
  azimp-crystal:
    title: Strontium Titanate crystal datasheet (Verneuil growth, PDF)
    id: azimp.ru PDF, file SrTiO3_Strontium_Titanate.pdf
    url: https://azimp.ru/upload/pdf-static/CRYSTAL/SrTiO3_Strontium_Titanate.pdf
    kind: datasheet
    license: supplier document, linked not reproduced
  ereztech-spec:
    title: Ereztech product specification SR0592, Strontium Titanium Oxide
    id: Ereztech SR0592; CAS 12060-59-2
    url: https://ereztech.com/product/strontium-titanium-oxide-12060-59-2/?pdf=2446
    kind: datasheet
    license: supplier document, linked not reproduced
  sam-msds:
    title: 'Stanford Advanced Materials: Material Safety Data Sheet, Strontium titanate'
    id: Version 2.0, revision date Sep 5, 2012; CAS 12060-59-2
    url: https://www.sputtertargets.net/Public/pdf/strontium-titanate-msds.pdf
    year: 2012
    kind: datasheet
    license: supplier document, linked not reproduced
  sam-substrate:
    title: 'Stanford Advanced Materials: Strontium titanate single-crystal substrate product page (catalog CY3345)'
    id: catalog CY3345
    url: https://www.samaterials.com/strontium-titanate-single-crystal-substrate.html
    kind: datasheet
    license: supplier page, linked not reproduced
  okhay2022:
    title: Low-Temperature Dielectric Response of Strontium Titanate Thin Films Manipulated by Zn Doping
    id: doi:10.3390/ma15030859 (Materials 15, 859)
    url: https://ria.ua.pt/bitstream/10773/36031/1/Mat15%282022%290859-Okhay.pdf
    year: 2022
    kind: paper
    license: CC BY 4.0
  usgs-mcs2026-strontium:
    title: Mineral Commodity Summaries 2026, Strontium
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-strontium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-mcs2026-titanium:
    title: Mineral Commodity Summaries 2026, Titanium and Titanium Dioxide
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-titanium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  wikipedia-sto:
    title: 'Wikipedia: Strontium titanate (used for composition, crystal system, space group and history only)'
    id: English Wikipedia article, Strontium titanate
    url: https://en.wikipedia.org/wiki/Strontium_titanate
    kind: web
    license: CC BY-SA 4.0
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 13
  unreachable: 3
  caveats: 3
  note: 'Read by an AI assistant on 2026-11-01 from the pages and PDFs fetched in that run. Unreachable in that run: the Lorad Chemical product page (no text returned to curl), the PubChem record (browser check page) and the American Elements SDS (HTTP 403). Wikipedia was used for composition, crystal system, space group and history only. Caveats: the supplier product page''s values are stated as theoretical in its footnote, so they are recorded as calculated; the crystal datasheet gives Mohs hardness as 6-6.5 without a form; the 2022 paper''s values are for thin films.'
story:
  recipe:
    line: SrTiO3 is a strontium titanium oxide with the cubic perovskite structure. Its formula is SrTiO3, with one strontium atom, one titanium atom and three oxygen atoms per formula unit. Single crystals are grown by the Verneuil method, according to the crystal datasheet from azimp.
    parts:
      - name: Strontium
        symbol: Sr
        role: The large cation in the perovskite framework. Strontium is mined as celestite, the strontium mineral named in the USGS summary.
      - name: Titanium
        symbol: Ti
        role: The smaller cation of the perovskite framework, sitting among the oxygen atoms.
      - name: Oxygen
        symbol: O
        role: Three oxygen atoms per formula unit complete the framework around the cations.
  risk_groups:
    - title: For people
      level: 1
      verdict: Low toxicity per the SDS; dust irritates
      lead: The Stanford safety data sheet gives strontium titanate a low order of toxicity and lists nuisance dust and mild irritation. No GHS hazard codes are recorded for it, and the sheet gives no toxicity values.
      points:
        - label: The powder
          line: The sheet lists the dust as a possible nuisance dust that can cause coughing and shortness of breath, and as a possible irritant to skin and eyes.
        - label: Strontium and titanium
          line: The sheet says strontium compounds have a low order of toxicity and describes titanium compounds as physiologically inert.
        - label: Exposure limits
          line: The sheet lists no OSHA PEL and no ACGIH TLV for the material, both printed as N/A.
    - title: If it fails
      lead: These results come from thin-film measurements and from the safety sheet, not from service incidents.
      points:
        - label: Thin films
          line: The 2022 paper says thin films usually have much higher dielectric loss than single crystals, because of point defects, local polar regions and stresses.
        - label: In a fire
          line: The sheet lists strontium oxide and titanium oxide as decomposition products, and says fumes from a fire are hazardous.
        - label: Strong acids and bases
          line: The sheet lists strong acids and strong bases as incompatible, and gives no reaction data.
    - title: Handling and storage
      points:
        - label: Keep it sealed
          line: Store in a tightly sealed container and wash thoroughly after handling. Keep it away from strong acids and strong bases.
        - label: Dust
          line: Use a HEPA filter vacuum for spills and avoid raising dust. The sheet recommends a NIOSH approved respirator, impervious gloves and safety glasses.
  why: Strontium titanate (SrTiO3, CAS 12060-59-2) is a cubic perovskite oxide that is sold as a powder and as single crystals. Its main commercial role is as a substrate. Crystal suppliers describe it as a popular substrate for growing oxide thin films and superconducting films, and the supplier page also lists special optical windows among its uses.
  uses:
    - where: Single-crystal substrates for oxide and superconducting thin films
      line: The Stanford Advanced Materials product page calls strontium titanate a popular crystal substrate for epitaxial growth of many oxide thin films, and says it is commonly used as a substrate for superconductor thin films.
    - where: Tunable thin-film microwave components
      line: A 2022 paper in Materials says that ferroelectric-related films are used in varactors, microwave filters, resonators and phase shifters. It adds that incipient ferroelectrics such as SrTiO3 are useful at cryogenic temperatures for tuning elements.
  can_do:
    - label: Substrate lattice
      benchmark: lattice_constant
      line: Serves as a cubic perovskite substrate for oxide films. The supplier product page prints a lattice constant of 3.905 Å and calls it a popular substrate for epitaxial growth.
    - label: Melting point
      benchmark: melting_point
      value: 2060 °C
      line: Melts at 2060 °C as a powder, per the Ereztech specification, and at 2353 K as a Verneuil crystal, per the crystal datasheet.
    - label: Thin-film permittivity peak
      benchmark: dielectric_peak_temperature
      value: 60 K
      line: Shows a diffuse permittivity peak near 60 K in an undoped sol-gel reference thin film, according to the 2022 paper.
    - label: Hardness
      benchmark: hardness_mohs
      value: 6 to 6.5
      line: Reaches a Mohs hardness of 6 to 6.5 for a Verneuil crystal, according to its datasheet.
  compare: 'The melting point is reported at two levels. The Ereztech specification and the Stanford safety sheet both give 2060 °C for the powder. The crystal datasheet gives 2353 K, and the supplier substrate page gives 2080 °C, which is the figure the crystal datasheet''s 2353 K converts to. Two density figures are on record: 5.12 g/cm3 from the crystal datasheet and 5.11 g/cm3 from the supplier substrate page, which the page footnote says is based on theoretical data. The crystal datasheet prints a dielectric constant of 300 with no temperature or frequency, and the substrate page prints about 300 at room temperature and 1 MHz. The sources read here give no bulk ceramic value.'
  compare_rows:
    - label: Melting point
      benchmark: melting_point
    - label: Density
      benchmark: density
    - label: Dielectric constant
      benchmark: dielectric_constant
  handling:
    - Store in a tightly sealed container and wash thoroughly after handling.
    - Avoid raising dust. Vacuum spills with a HEPA filter and place the material in a closed container for disposal.
    - Keep it away from strong acids and strong bases, which the safety sheet lists as incompatible.
  good_for:
    - Oxide thin-film growth. The supplier page calls it a popular crystal substrate for epitaxial growth of many oxide thin films.
    - Low-temperature tunable parts. The 2022 paper says it is useful at cryogenic temperatures for tuning elements.
  watch_out:
    - Thin films have much higher dielectric loss than single crystals, according to the 2022 paper.
    - Hardness is not settled. The crystal datasheet gives a Mohs hardness of 6 to 6.5, and Wikipedia gives a lower Mohs value for synthetic material.
    - The supplier substrate values are theoretical, according to the footnote on that page, so they are calculated rather than measured.
  verdict: Strontium titanate is a well-recorded oxide substrate. Its melting-point figures differ between suppliers (2060 °C and 2080 °C), and its datasheets give no strength, toxicity or space-environment data, so it is best treated as a substrate and a dielectric material only.