spore: profile id: transition-metal-silicides spore_version: 0.2 family: carbide-nitride-boride-ceramics name: Transition-metal silicides (disilicides) abbreviation: MSi2 role: microelectronics contact silicides and oxidation-resistant silicide coatings (WSi2, TiSi2, TaSi2, CrSi2, NbSi2, FeSi2) category: ceramics type: ultra-high-temperature-ceramics summary: | Transition-metal disilicides share the formula MSi2. The sources read here cover six of them. WSi2 has a density of 9.3 g/cm3 and a melting point of 2160 degC (Stanford Advanced Materials). TiSi2 in the low-resistivity C54 phase has a thin-film resistivity of 12 to 24 uOhm·cm and is used as an interconnect and gate silicide in integrated circuits. TaSi2 melts at 2200 degC with a density of 9.14 g/cm3 (Micron Metals). CrSi2 melts at 1490 degC and NbSi2 at 1950 degC. Beta-FeSi2 is a semiconductor with a quoted indirect gap of 0.73 to 0.78 eV, studied as a thermoelectric. NbSi2 is studied as an oxidation-resistant coating for niobium alloys, but a Hokkaido University study reports accelerated oxidation above 1073 K in air. best_for: Low-resistivity silicide contacts in microelectronics (TiSi2 C54, WSi2) and high-melting silicide coatings weakest_at: Oxidation at intermediate temperatures for NbSi2 and CrSi2, and no flight or space data for any of the six compounds identity: formula: MSi2, with M = W, Ti, Ta, Cr, Nb or Fe source: pubchem-wsi2 where: PubChem compound records CID 9794752 (WSi2), 6336889 (TiSi2), 6336888 (TaSi2), 13710602 (CrSi2), 6336884 (NbSi2) and 6336880 (FeSi2); MolecularFormula property of each tags: environments: [] stresses: - extreme-heat applications: - electronics-and-chips - structures - thermal-control properties: - benchmark: density label: Density, WSi2 powder value: 9.3 unit: g/cm3 scope: material conditions: form: powder grade: WSi2 powder, supplier listing method: Density field of the supplier product page status: ground source: samaterials-wsi2 where: Product specification block, Density field - benchmark: melting_point label: Melting point, WSi2 powder value: 2160 unit: degC scope: material conditions: form: powder printed: 3,920°F (2,160°C) method: Melting Point field of the supplier product page status: ground source: samaterials-wsi2 where: Product specification block, Melting Point field - benchmark: electrical_resistivity label: Electrical resistivity, C54 TiSi2 thin film value: 12 value_high: 24 bound: range unit: uOhm·cm scope: material conditions: phase: C54 (low-resistivity orthorhombic phase) form: thin film printed: 12-24 (μΩ − cm) method: Resistivity row of Table 150a, column C54, copied as printed status: ground source: globalsino-tisi2 where: Table 150a, Properties of TiSi2 materials, resistivity row, C54 column - benchmark: density label: Density, C54 TiSi2 (supplier theoretical) value: 4.13 unit: g/cm3 scope: material conditions: phase: C54 basis: theoretical value printed by the supplier method: Density field of the sputtering target page, printed with a tilde (approximate) status: ground note: Supplier figure printed as approximate (~4.13 g/cm3). Not a measured bulk density. source: sputtertargets-tisi2 where: Specification table, Density field - benchmark: melting_point label: Melting point, C54 TiSi2 (supplier approximate) value: 1500 unit: degC scope: material conditions: phase: C54 basis: approximate value printed by the supplier method: Melting Point field of the sputtering target page, printed as approximately 1500 degC status: ground note: Supplier figure printed as approximate. The Table 150a melting row in the globalsino page is not used because its column layout could not be confirmed. source: sputtertargets-tisi2 where: Specification table, Melting Point field - benchmark: density label: Density, TaSi2 (theoretical, Micron Metals) value: 9.14 unit: g/cm3 scope: material conditions: form: powder grade: TaSi2 powder method: Density field of the Micron Metals product page status: ground source: micronmetals-tasi2 where: Product specification table, Density field - benchmark: melting_point label: Melting point, TaSi2 (Micron Metals) value: 2200 unit: degC scope: material conditions: form: powder printed: 2200°C / 3992°F method: Melting Point field of the Micron Metals product page status: ground source: micronmetals-tasi2 where: Product specification table, Melting Point field - benchmark: electrical_resistivity label: Electrical resistivity, TaSi2 (supplier bulk figure) value: 35 value_high: 50 bound: range unit: uOhm·cm scope: material conditions: basis: bulk figure printed by the supplier; the page notes that film values depend on deposition and annealing phase: hexagonal C40 method: Electrical Resistivity (Bulk) field of the sputtering target page status: ground note: Supplier range, printed as approximately 35 to 50 uOhm·cm. Not a measured value for a stated test method. source: sputtertargets-tasi2 where: Specification table, Electrical Resistivity (Bulk) field - benchmark: melting_point label: Melting point, CrSi2 (Micron Metals) value: 1490 unit: degC scope: material conditions: form: powder printed: 1490°C / 2714°F method: Melting Point field of the Micron Metals CrSi2 product page status: ground source: micronmetals-crsi2 where: Product specification table, Melting Point field - benchmark: density label: Density, CrSi2 (supplier evaporation material) value: 4.91 unit: g/cm3 scope: material conditions: form: evaporation material grade: CrSi2 method: Density field of the supplier evaporation-materials page status: ground note: Micron Metals prints 5.5 for CrSi2 with no unit, which is not used (see gaps). source: sputtertargets-crsi2 where: Specification table, Density field - benchmark: melting_point label: Melting point, NbSi2 (Micron Metals) value: 1950 unit: degC scope: material conditions: form: powder printed: 1950°C / 3542°F method: Melting Point field of the Micron Metals NbSi2 product page status: ground source: micronmetals-nbsi2 where: Product specification table, Melting Point field - benchmark: band_gap label: Indirect band gap, beta-FeSi2 (values quoted in the arXiv paper) value: 0.73 value_high: 0.78 bound: range unit: eV scope: material conditions: phase: beta-FeSi2 transition: indirect basis: two experimental values quoted by the paper from earlier work (Filonov et al. optical absorption; Radermacher et al. photothermal deflection) method: Quoted in the discussion of experimental band-gap results status: ground note: Custom property name, not in spores/property-canon.yaml. Values are quoted from earlier work, not measured in this run. source: arxiv-fesi2 where: Section on experimental band gap of beta-FeSi2, paragraph beginning "Experimental results on the band gap" corrosion: - environment: Air at high temperature (protective silica scale) headline: WSi2 is described by its supplier as having good oxidation resistance. effect: The supplier describes WSi2 powder as a conductive ceramic with a high melting point and good oxidation resistance. No rate or temperature limit is printed on the page read. rating: low conditions: atmosphere: air temperature: not stated source: samaterials-wsi2 where: Product description paragraph - environment: Air at 773 to 1673 K (sintered NbSi2) headline: NbSi2 oxidises fast above 1073 K in air because its oxide scale becomes porous. effect: The study oxidised sintered NbSi2 in air from 773 to 1673 K and reports accelerated oxidation at 1073 K and above. The accelerated oxidation was attributed to a porous oxide layer. The authors describe the oxidation behaviour as complicated and dependent on temperature, and call NbSi2 a promising candidate for coating Nb-base alloys. rating: moderate conditions: atmosphere: air temperature: 773 to 1673 K (sintered NbSi2) source: hokudai-nbsi2 where: Abstract, first paragraph - environment: Air, mixed-oxidation behaviour of CrSi2 headline: Supplier notes oxidation resistance for CrSi2 but gives no rate or limit. effect: Micron Metals lists oxidation resistance among the properties of CrSi2 powder, but the page read gives no oxidation rate, temperature limit or scale description, so no rating beyond a supplier note is recorded. rating: unknown conditions: atmosphere: air temperature: not stated source: micronmetals-crsi2 where: Product description risks: hazards: - text: PubChem lists WSi2 as not classified under GHS for 100% (3 of 3) of the reports it holds, so no hazard label is recorded for WSi2 in that record. ghs: [] source: pubchem-wsi2 where: Safety and Hazards, GHS Classification (CID 9794752) - text: 'PubChem aggregated GHS for CrSi2 (CID 13710602): H302, H312 and H332 (18.1 percent of reports each), H315 and H319 (79.6 percent each), H317 (20.4 percent). Signal word Warning.' ghs: - H302 - H312 - H315 - H317 - H319 - H332 source: pubchem-crsi2 where: Safety and Hazards, GHS Classification (CID 13710602) - text: 'PubChem aggregated GHS for beta-FeSi2 (CID 6336880): H315 and H319 (66.7 percent of reports each). Signal word Warning.' ghs: - H315 - H319 source: pubchem-fesi2 where: Safety and Hazards, GHS Classification (CID 6336880) - text: 'PubChem aggregated GHS for NbSi2 (CID 6336884): H319 (100 percent of the reports it holds). Signal word Warning.' ghs: - H319 source: pubchem-nbsi2 where: Safety and Hazards, GHS Classification (CID 6336884) failure_risks: - mode: Accelerated oxidation and porous scale on NbSi2 coatings above 1073 K trigger: Sustained exposure to air at 1073 K and above consequence: The porous oxide layer does not protect the substrate, so the coating loses its oxidation barrier. The authors report the cause as a porous oxide layer formed during accelerated oxidation. severity: moderate source: hokudai-nbsi2 where: Abstract, first paragraph side_effects: [] handling: - text: PubChem reports H315, H317 and H319 for CrSi2 and H315 and H319 for beta-FeSi2 (skin and eye irritation), so avoid skin and eye contact and avoid breathing dust. source: pubchem-crsi2 where: Safety and Hazards, GHS Classification (CID 13710602) mitigations: [] uses: - application: electronics-and-chips device: Silicide contacts and gate electrodes in integrated circuits (TiSi2, C54 phase) example: TiSi2 is commonly applied as interconnects in ultra-large-scale integrated circuits and as gate electrodes in MOS transistors, because it has low resistivity and good electrical contact with silicon. source: globalsino-tisi2 where: Introduction paragraph of the TiSi2 entry, before Table 150a - application: electronics-and-chips device: Contact material and polysilicon shunt in microelectronics (WSi2) example: The supplier says WSi2 is mostly used in microelectronics as a contact material because of its small resistance, and as a shunt over polysilicon lines to raise conductivity and signal speed. source: samaterials-wsi2 where: Product description paragraph - application: electronics-and-chips device: Semiconductor metallization (TaSi2 sputtering targets) example: The supplier describes TaSi2 as a critical material in semiconductor metallization, with a hexagonal C40 structure that is the stable low-resistivity phase for thin films. source: sputtertargets-tasi2 where: Product description and phase table - application: structures device: Oxidation-protective silicide coating on niobium-base alloys (research) example: The Hokkaido study calls NbSi2 a promising candidate as a coating material for Nb-base alloys, but reports complicated oxidation behaviour that depends on temperature. This is a research finding, not a flight use. source: hokudai-nbsi2 where: Abstract, first sentence - application: thermal-control device: Beta-FeSi2 thermoelectric material for waste-heat conversion (research) example: A review describes beta-FeSi2 as a sustainable thermoelectric material because it is abundant, non-toxic and environmentally compatible. source: pmc-fesi2-review where: Abstract, first sentence supply: - subject: Tungsten (WSi2) abundance: 'USGS: world mine production of tungsten in 2025 was 85,000 t (rounded), with China reserves of 2,500,000 t.' producers: - country: China share_percent: 78.8 year: 2025 - country: Vietnam share_percent: 3.5 year: 2025 - country: Kazakhstan share_percent: 2.8 year: 2025 - country: Russia share_percent: 2.4 year: 2025 - country: Bolivia share_percent: 2 year: 2025 substitutes: [] source: usgs-mcs2026-tungsten where: World Mine Production and Reserves table, 2025 column (world total 85,000 rounded; shares calculated by Space Mushroom against that total) - subject: Titanium (TiSi2, sponge metal) abundance: 'USGS: sponge production table, 2025 estimate, world total printed as 370,000 (rounded). The United States did not produce titanium sponge in 2025.' 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 - country: Saudi Arabia share_percent: 3.2 year: 2025 substitutes: - 'USGS: few materials have titanium metal''s strength-to-weight ratio and corrosion resistance; in high-strength applications it competes with aluminum, composites, intermetallics, steel and superalloys.' source: usgs-mcs2026-titanium where: Sponge production table, 2025 estimate column (shares calculated by Space Mushroom against the 370,000 world total); Domestic Production and Use; Substitutes - subject: Chromium (CrSi2) abundance: 'USGS: mine production table, 2025 estimate, world total printed as 51,000 (rounded).' producers: - country: South Africa share_percent: 45.1 year: 2025 - country: Turkey share_percent: 17.6 year: 2025 - country: Kazakhstan share_percent: 13.7 year: 2025 - country: India share_percent: 5.9 year: 2025 - country: Brazil share_percent: 3.9 year: 2025 source: usgs-mcs2026-chromium where: Mine production table, 2025e column (world total 51,000 rounded; shares calculated by Space Mushroom against that total) - subject: Niobium (NbSi2) abundance: 'USGS: world mine production of niobium 2025 estimate printed as 112,000 (rounded); reserves printed as more than 21,000,000.' producers: - country: Brazil share_percent: 92.9 year: 2025 - country: Canada share_percent: 5.4 year: 2025 - country: Russia share_percent: 0.3 year: 2025 source: usgs-mcs2026-niobium where: Mine production table, 2025e column (world total 112,000 rounded; shares calculated by Space Mushroom against that total) - subject: Tantalum (TaSi2) abundance: 'USGS: world mine production of tantalum 2025 estimate printed as 2,500 (rounded).' producers: - country: Congo (Kinshasa) share_percent: 52 year: 2025 - country: Rwanda share_percent: 16 year: 2025 - country: Nigeria share_percent: 15.6 year: 2025 - country: China share_percent: 3.2 year: 2025 source: usgs-mcs2026-tantalum where: Mine production table, 2025e column (world total 2,500 rounded; shares calculated by Space Mushroom against that total) media: [] documents: - title: Stanford Advanced Materials, tungsten disilicide (WSi2) powder product page type: datasheet url: https://www.samaterials.com/tungsten/1475-tungsten-disilicide-wsi2-powder.html year: 2026 - title: Micron Metals, tantalum disilicide powder product page type: datasheet url: https://micronmetals.com/product/tantalum-disilicide-powder year: 2026 - title: Micron Metals, chromium disilicide powder product page type: datasheet url: https://micronmetals.com/product/chromium-disilicide-powder/ year: 2026 - title: Micron Metals, niobium disilicide powder product page type: datasheet url: https://micronmetals.com/product/niobium-disilicide-powder/ year: 2026 - title: Hokkaido University, Improvement of Oxidation Resistance of NbSi2 by Addition of Boron (Materials Science Forum 502) type: paper url: https://eprints.lib.hokudai.ac.jp/repo/huscap/all/733/NbSi2.pdf - title: PubChem compound records for the six disilicides (GHS classification) type: database url: https://pubchem.ncbi.nlm.nih.gov/compound/9794752 year: 2026 - title: USGS Mineral Commodity Summaries 2026, Tungsten type: report url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tungsten.pdf year: 2026 gaps: - Six compounds are covered in one file, so most families have only two to four sourced properties. TaSi2, CrSi2, NbSi2 and FeSi2 have no sourced electrical-resistivity or hardness value except TaSi2 (supplier bulk range). - No melting point for FeSi2 found. The PMC review and the arXiv paper note incongruent melting but print no temperature in the parts read. - Density of NbSi2 and CrSi2 from Micron Metals is printed with no unit (5.6 and 5.5), so it is left out. The sputtering-target page gives 4.91 g/cm3 for CrSi2; no sourced density for NbSi2. - Crystal structures are stated by sources (C54 for TiSi2 in the sputtering target and globalsino pages, C40 hexagonal for TaSi2 and NbSi2 and CrSi2) but are not recorded as identity fields. - Melting point of TiSi2 C54 is a supplier approximate figure (about 1500 degC); the Table 150a melting row (1540) is not used because the column could not be matched to C54 with confidence. - Band-gap values for FeSi2 are quoted from earlier work by the arXiv paper, not measured in this run. Direct-gap value (0.85 eV, thin film) was not read on a fetched page. - Hazard data rest on the PubChem aggregate. No safety data sheet for any of the six compounds was read in this run; PubChem returns no GHS classification text for TiSi2 or TaSi2 in the record read. - 'Supply: USGS critical-mineral list status for tungsten, titanium, tantalum, chromium, niobium and silicon was not read in this run, so critical_lists are left out. Silicon supply is not repeated here (see the MoSi2 profile).' - 'Space use: no flight, radiation, vacuum or atomic-oxygen data for any of the six compounds were read in this run.' - The NbSi2 coating research cited here is laboratory oxidation work. Coating life and pest-oxidation range are not quantified in the parts read. - 'Custom property names used because they are not in spores/property-canon.yaml: band_gap.' - Recipe atomic weights are for the elemental metals and silicon; PubChem compound records for the disilicides themselves give MolecularFormula, not atomic weights. sources: samaterials-wsi2: title: Stanford Advanced Materials, Tungsten Disilicide Powder (WSi2) product page url: https://www.samaterials.com/tungsten/1475-tungsten-disilicide-wsi2-powder.html kind: datasheet license: supplier product page, cited not reproduced globalsino-tisi2: title: Practical Electron Microscopy and Database, page 150 (titanium disilicide, Table 150a) url: https://www.globalsino.com/EM/page150.html kind: web license: web reference, cited not reproduced sputtertargets-tisi2: title: Sputter Targets, Titanium Silicide (TiSi2) planar sputtering target page url: https://www.sputtertargets.net/st11217-titanium-silicide-tisi2-planar-sputtering-target/ kind: datasheet license: supplier product page, cited not reproduced sputtertargets-tasi2: title: Sputter Targets, Tantalum Silicide (TaSi2) planar target page url: https://www.sputtertargets.net/st11216-tantalum-silicide-planar-target-tasi2-target/ kind: datasheet license: supplier product page, cited not reproduced sputtertargets-crsi2: title: Sputter Targets, Chromium silicide evaporation materials page url: https://www.sputtertargets.net/chromium-silicide-evaporation-materials.html kind: datasheet license: supplier product page, cited not reproduced micronmetals-tasi2: title: Micron Metals, Tantalum Disilicide Powder product page url: https://micronmetals.com/product/tantalum-disilicide-powder kind: datasheet license: supplier product page, cited not reproduced micronmetals-crsi2: title: Micron Metals, Chromium Disilicide Powder product page url: https://micronmetals.com/product/chromium-disilicide-powder/ kind: datasheet license: supplier product page, cited not reproduced micronmetals-nbsi2: title: Micron Metals, Niobium Disilicide Powder product page url: https://micronmetals.com/product/niobium-disilicide-powder/ kind: datasheet license: supplier product page, cited not reproduced arxiv-fesi2: title: Thermoelectric properties of beta-FeSi2 (arXiv 1308.6529) url: https://arxiv.org/pdf/1308.6529 kind: paper license: arXiv, cited not reproduced hokudai-nbsi2: title: Kurokawa, Yamauchi, Matsushita, Improvement of Oxidation Resistance of NbSi2 by Addition of Boron, Materials Science Forum 502 url: https://eprints.lib.hokudai.ac.jp/repo/huscap/all/733/NbSi2.pdf kind: paper license: university repository, cited not reproduced pmc-fesi2-review: title: Strategies to improve the thermoelectric performance of iron silicide-based materials (PMC) url: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12667310/ kind: paper license: open access (PMC), cited not reproduced pubchem-wsi2: title: PubChem compound CID 9794752, tungsten disilicide (MolecularFormula Si2W) url: https://pubchem.ncbi.nlm.nih.gov/compound/9794752 kind: database license: PubChem public database pubchem-tisi2: title: PubChem compound CID 6336889, titanium disilicide url: https://pubchem.ncbi.nlm.nih.gov/compound/6336889 kind: database license: PubChem public database pubchem-tasi2: title: PubChem compound CID 6336888, tantalum disilicide url: https://pubchem.ncbi.nlm.nih.gov/compound/6336888 kind: database license: PubChem public database pubchem-crsi2: title: PubChem compound CID 13710602, chromium disilicide (GHS classification) url: https://pubchem.ncbi.nlm.nih.gov/compound/13710602 kind: database license: PubChem public database pubchem-nbsi2: title: PubChem compound CID 6336884, niobium disilicide (GHS classification) url: https://pubchem.ncbi.nlm.nih.gov/compound/6336884 kind: database license: PubChem public database pubchem-fesi2: title: PubChem compound CID 6336880, iron disilicide (GHS classification) url: https://pubchem.ncbi.nlm.nih.gov/compound/6336880 kind: database license: PubChem public database pubchem-w: title: PubChem compound CID 23964, tungsten (MolecularWeight 183.84) url: https://pubchem.ncbi.nlm.nih.gov/compound/23964 kind: database license: PubChem public database pubchem-ti: title: PubChem compound CID 23963, titanium (MolecularWeight 47.867) url: https://pubchem.ncbi.nlm.nih.gov/compound/23963 kind: database license: PubChem public database pubchem-ta: title: PubChem compound CID 23956, tantalum (MolecularWeight 180.9479) url: https://pubchem.ncbi.nlm.nih.gov/compound/23956 kind: database license: PubChem public database pubchem-cr: title: PubChem compound CID 23976, chromium (MolecularWeight 51.996) url: https://pubchem.ncbi.nlm.nih.gov/compound/23976 kind: database license: PubChem public database pubchem-nb: title: PubChem compound CID 23936, niobium (MolecularWeight 92.90637) url: https://pubchem.ncbi.nlm.nih.gov/compound/23936 kind: database license: PubChem public database pubchem-fe: title: PubChem compound CID 23925, iron (MolecularWeight 55.84) url: https://pubchem.ncbi.nlm.nih.gov/compound/23925 kind: database license: PubChem public database pubchem-si: title: PubChem compound CID 5461123, silicon (MolecularWeight 28.085) url: https://pubchem.ncbi.nlm.nih.gov/compound/5461123 kind: database license: PubChem public database usgs-mcs2026-tungsten: title: Mineral Commodity Summaries 2026, Tungsten url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tungsten.pdf kind: report license: public domain (USGS) usgs-mcs2026-titanium: title: Mineral Commodity Summaries 2026, Titanium (sponge metal) url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-titanium.pdf kind: report license: public domain (USGS) usgs-mcs2026-chromium: title: Mineral Commodity Summaries 2026, Chromium url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf kind: report license: public domain (USGS) usgs-mcs2026-niobium: title: Mineral Commodity Summaries 2026, Niobium url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf kind: report license: public domain (USGS) usgs-mcs2026-tantalum: title: Mineral Commodity Summaries 2026, Tantalum url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tantalum.pdf kind: report license: public domain (USGS) license: CC-BY-4.0 updated: '2026-10-26' review: status: draft method: assistant checked_values: 12 unreachable: 3 caveats: 6 note: 'Written in this run from the Stanford Advanced Materials WSi2 page, the Globalsino TiSi2 page, three sputtering-target pages (TiSi2, TaSi2 and CrSi2), Micron Metals pages (TaSi2, CrSi2, NbSi2), the arXiv FeSi2 paper, the Hokkaido NbSi2 paper, the PMC iron silicide review, PubChem GHS records and USGS MCS 2026 tables. Not reachable or not used: the AmericanElements WSi2 page (Cloudflare block), the RSC NbSi2 paper (no text), and the Nemanich TiSi2 PDF (404).' story: recipe: line: 'Each compound is a 1:2 metal-to-silicon phase. Per formula unit: one transition-metal atom and two silicon atoms (WSi2, TiSi2, TaSi2, CrSi2, NbSi2 or FeSi2). The metal parts below are one per compound, not a single mixture.' parts: - name: Silicon symbol: Si atoms: 2 atomic_weight: 28.085 role: Two per formula unit. Silicon forms the disilicide lattice with the metal and, in microelectronics contacts, bonds to the silicon substrate. - name: Tungsten symbol: W atoms: 1 atomic_weight: 183.84 role: The metal in WSi2, which is used for microelectronics contacts and has a melting point of 2160 degC. - name: Titanium symbol: Ti atoms: 1 atomic_weight: 47.867 role: The metal in TiSi2. The low-resistivity C54 phase is the one used for contacts. - name: Tantalum symbol: Ta atoms: 1 atomic_weight: 180.9479 role: The metal in TaSi2, used in semiconductor metallization. - name: Chromium symbol: Cr atoms: 1 atomic_weight: 51.996 role: The metal in CrSi2. - name: Niobium symbol: Nb atoms: 1 atomic_weight: 92.90637 role: The metal in NbSi2, studied as an oxidation-resistant coating for niobium alloys. - name: Iron symbol: Fe atoms: 1 atomic_weight: 55.84 role: The metal in beta-FeSi2, a semiconductor studied for thermoelectric use. risk_groups: - title: For people level: 0 verdict: Irritant reports for CrSi2 and FeSi2 lead: PubChem's aggregated GHS data for CrSi2 and beta-FeSi2 give skin and eye irritation codes. The WSi2 record has no classification. No supplier safety data sheet for these powders was read in this run. points: - label: Powder line: CrSi2 is reported with H302, H312 and H332 (harmful if swallowed, in contact with skin or if inhaled) for part of its reports, and with H315, H317 and H319 for most of them. - label: Eyes and skin line: beta-FeSi2 and NbSi2 are reported with H315 or H319 (skin or serious eye irritation). - title: If a coating or element fails lead: These points come from the NbSi2 oxidation study and the sources on use. points: - label: Accelerated oxidation line: NbSi2 oxidised fast above 1073 K in air, because the oxide scale became porous. A coating in that range would not protect the niobium alloy. - label: Contacts line: TiSi2 and WSi2 contacts depend on low resistivity; the TiSi2 C54 thin film is quoted at 12 to 24 uOhm·cm. - title: Handling points: - label: Dust line: Avoid breathing and handling the powder, as PubChem's irritation codes for CrSi2 and beta-FeSi2 suggest. why: Transition-metal disilicides combine a high melting point with low electrical resistivity. TiSi2 in the C54 phase and WSi2 are used as contacts and gate silicides in integrated circuits. TaSi2 is used in semiconductor metallization. NbSi2 is studied as an oxidation-resistant coating for niobium alloys, but it oxidises fast above 1073 K. beta-FeSi2 is a semiconductor with an indirect gap of 0.73 to 0.78 eV, studied for thermoelectric use. The sources read here give melting points of 1490 to 2200 degC for four of the compounds, and no flight or space data. uses: - where: Microelectronics contacts line: TiSi2 is commonly applied as interconnects and gate electrodes in integrated circuits. WSi2 is mostly used as a contact material and as a shunt over polysilicon lines, according to the supplier. TaSi2 is used in semiconductor metallization. - where: Oxidation-protective coating (research) line: NbSi2 is described as a promising coating for niobium-base alloys. Its oxidation is complicated and depends on temperature, so it is a research candidate, not a production coating. - where: Thermoelectric research line: beta-FeSi2 is studied as a sustainable thermoelectric material because it is abundant and non-toxic. - where: Space applications line: No flight, space or lunar source for any of the six compounds was read in this run. can_do: - label: Melt benchmark: melting_point value: 2160 degC line: WSi2 melts at 2160 degC according to its supplier, and TaSi2 at 2200 degC. CrSi2 melts at 1490 degC and NbSi2 at 1950 degC. - label: Low resistivity benchmark: electrical_resistivity value: 12 to 24 uOhm·cm line: The C54 TiSi2 thin film has a resistivity of 12 to 24 uOhm·cm. TaSi2 bulk is quoted at 35 to 50 uOhm·cm by a supplier. - label: Density benchmark: density value: 9.3 g/cm3 line: WSi2 powder has a density of 9.3 g/cm3 and TaSi2 has 9.14 g/cm3. CrSi2 has 4.91 g/cm3 and C54 TiSi2 about 4.13 g/cm3 (supplier, approximate). compare: The compounds split into two groups by density and melting point. WSi2 and TaSi2 are dense (9.3 and 9.14 g/cm3) and melt above 2160 degC. CrSi2 and TiSi2 are lighter and melt near 1500 degC. For microelectronics contacts, the TiSi2 C54 phase has the lowest resistivity quoted here (12 to 24 uOhm·cm, thin film), while TaSi2 bulk is quoted at 35 to 50 uOhm·cm. compare_rows: - label: Density benchmark: density - label: Melting point benchmark: melting_point - label: Electrical resistivity benchmark: electrical_resistivity handling: - PubChem lists irritation codes for CrSi2 and beta-FeSi2. Avoid skin and eye contact and avoid breathing the dust. - NbSi2 oxidises fast above 1073 K in air, so do not expect a coating to hold above that temperature without a protective layer. good_for: - Silicide contacts in integrated circuits. TiSi2 C54 thin film is quoted at 12 to 24 uOhm·cm, and WSi2 is used as a contact material. - High-melting silicide powders. WSi2 melts at 2160 degC and TaSi2 at 2200 degC according to the suppliers. watch_out: - 'NbSi2 oxidation: accelerated above 1073 K, with a porous oxide layer.' - Density and melting point differ between suppliers. Use the supplier certificate for the grade you buy. - No space, radiation or vacuum data for any of the six compounds. verdict: The six disilicides are useful as contacts and high-melting powders. Only TiSi2 and WSi2 have a clear microelectronics use in the sources read, and NbSi2 coatings do not yet hold up above about 1073 K.