spore: profile id: terbium spore_version: 0.2 family: rare-earth-metals name: Terbium abbreviation: Tb role: green phosphor activator, magnetostrictive alloy component (Terfenol-D) and Faraday rotator garnet category: metals type: heavy-metals summary: | Terbium is the element Tb (atomic number 65), a silvery-white rare-earth metal that is malleable, ductile and soft enough to be cut with a knife. It has a density of 8.229 g/cm3 at 20 °C and a melting point of 1356 °C (Wikipedia). It is not found as a mineral of its own: it occurs with other rare earths in monazite and xenotime, with a crust abundance of 1.2 mg/kg (Wikipedia). The metal is made by reducing the anhydrous chloride or fluoride with calcium metal (Wikipedia). Most of the world's terbium goes into green phosphors, and the alloy Terfenol-D, which expands or contracts in a magnetic field, is used in actuators and sonar (Wikipedia). The metal tarnishes in air, reacts with hot water and dilute acid, and is flammable as dust, so it needs dry, inert handling (Ames SDS, WebElements). best_for: Green phosphors for lighting and displays, and magnetostrictive Terfenol-D actuators (Wikipedia; NASA 1991 report) weakest_at: Dust and fines that ignite, and metal that releases hydrogen on contact with water or dilute acid (Ames SDS, WebElements) identity: formula: Tb (element, atomic number 65); unalloyed metal sold as pieces, ingot, rod, foil, sheet and target by the Ames Laboratory cas: 7440-27-9 source: pubchem-tb where: Other Identifiers, CAS entry (PubChem CID 23958); EC number 231-137-6 is printed in the Ames SDS, section 3 tags: environments: [] applications: - mechanisms - optics-and-cameras - electronics-and-chips properties: - benchmark: density label: Density, terbium (Wikipedia infobox) value: 8.229 unit: g/cm3 scope: material conditions: temperature: 20 °C unit_in_source: 8.229 g/cm3 method: Value printed in the Wikipedia infobox status: ground source: wikipedia-tb where: Infobox, row Density (at 20° C) 8.229 g/cm3 - benchmark: density label: Relative density, terbium value: 8.23 unit: g/cm3 scope: material conditions: temperature: not stated unit_in_source: 8.230 g/cc method: Value printed in the Ames Laboratory safety data sheet, section 9 status: ground source: ames-tb-sds where: Section 9 Physical and Chemical Properties, row Relative Density (Specific Gravity) 8.230 g/cc - benchmark: melting_point label: Melting point, terbium (Wikipedia infobox) value: 1356 unit: °C scope: material conditions: pressure: not stated unit_in_source: 1629 K (1356 °C, 2473 °F) method: Value printed in the Wikipedia infobox status: ground source: wikipedia-tb where: Infobox, row Melting point, 1629 K (1356 °C, 2473 °F) - benchmark: melting_point label: Melting point, terbium (Ames SDS) value: 1356 unit: °C scope: material conditions: pressure: not stated unit_in_source: 1356 oC method: Value printed in the Ames Laboratory safety data sheet, section 9 status: ground source: ames-tb-sds where: Section 9, row Melting Point 1356 oC - benchmark: boiling_point label: Boiling point, terbium (Wikipedia infobox) value: 3123 unit: °C scope: material conditions: pressure: not stated unit_in_source: 3396 K (3123 °C, 5653 °F) method: Value printed in the Wikipedia infobox status: ground note: The Ames SDS and PubChem give 3230 °C, about 107 °C higher. Both values are kept. source: wikipedia-tb where: Infobox, row Boiling point, 3396 K (3123 °C, 5653 °F) - benchmark: boiling_point label: Boiling point, terbium (PubChem) value: 3230 unit: °C scope: material conditions: pressure: 760 mmHg method: Value printed in the PubChem experimental properties section status: ground source: pubchem-tb where: Chemical and Physical Properties, Experimental Properties, Boiling Point 3230 °C @760 mm Hg - benchmark: boiling_point label: Boiling point, terbium (Ames SDS) value: 3230 unit: °C scope: material conditions: pressure: not stated unit_in_source: 3230 oC method: Value printed in the Ames Laboratory safety data sheet, section 9 status: ground source: ames-tb-sds where: Section 9, row Boiling Point 3230 oC - benchmark: specific_heat label: Specific heat capacity, terbium (Wikipedia infobox) value: 181.904 unit: J/(kg·K) scope: material conditions: temperature: not stated in the infobox method: Value printed in the Wikipedia infobox status: ground source: wikipedia-tb where: Infobox, row Specific heat capacity 181.904 J/(kg·K) - benchmark: thermal_conductivity label: Thermal conductivity, terbium (Wikipedia infobox) value: 11.1 unit: W/(m·K) scope: material conditions: temperature: not stated in the infobox method: Value printed in the Wikipedia infobox status: ground source: wikipedia-tb where: Infobox, row Thermal conductivity 11.1 W/(m⋅K) - benchmark: thermal_conductivity label: Thermal conductivity, terbium (WebElements) value: 11 unit: W/(m·K) scope: material conditions: temperature: not stated unit_in_source: 11 W m-1 K-1 method: Value printed on the WebElements physical-properties page status: ground source: webelements-tb where: Heat and conduction, row Thermal conductivity 11 W m-1 K-1 - benchmark: cte label: Coefficient of thermal expansion, terbium (Wikipedia infobox) value: 10.3 unit: µm/(m·K) scope: material conditions: temperature: room temperature form: polycrystalline unit_in_source: 10.3 µm/(m⋅K) method: Value printed in the Wikipedia infobox, row Thermal expansion at r.t. poly status: ground source: wikipedia-tb where: Infobox, row Thermal expansion, at r.t. poly 10.3 µm/(m⋅K) - benchmark: cte label: Coefficient of linear thermal expansion, terbium (WebElements) value: 10.3 unit: ppm/K scope: material conditions: temperature: not stated unit_in_source: 10.3 × 10-6 K-1 method: Value printed on the WebElements physical-properties page status: ground source: webelements-tb where: Heat and conduction, row Coefficient of linear thermal expansion 10.3 × 10-6 K-1 - benchmark: elastic_modulus label: Young's modulus, terbium (Wikipedia infobox) value: 55.7 unit: GPa scope: material conditions: temperature: not stated in the infobox method: Value printed in the Wikipedia infobox status: ground source: wikipedia-tb where: Infobox, row Young's modulus 55.7 GPa - benchmark: elastic_modulus label: Young's modulus, terbium (WebElements) value: 56 unit: GPa scope: material conditions: temperature: not stated method: Value printed on the WebElements physical-properties page status: ground source: webelements-tb where: Elastic properties, row Young's modulus 56 GPa - benchmark: shear_modulus label: Shear modulus, terbium (Wikipedia infobox) value: 22.1 unit: GPa scope: material conditions: temperature: not stated in the infobox method: Value printed in the Wikipedia infobox status: ground source: wikipedia-tb where: Infobox, row Shear modulus 22.1 GPa - benchmark: shear_modulus label: Rigidity modulus, terbium (WebElements) value: 22 unit: GPa scope: material conditions: temperature: not stated method: Value printed on the WebElements physical-properties page; WebElements calls the shear modulus the rigidity modulus status: ground source: webelements-tb where: Elastic properties, row Rigidity modulus 22 GPa - benchmark: bulk_modulus label: Bulk modulus, terbium (Wikipedia infobox) value: 38.7 unit: GPa scope: material conditions: temperature: not stated in the infobox method: Value printed in the Wikipedia infobox status: ground source: wikipedia-tb where: Infobox, row Bulk modulus 38.7 GPa - benchmark: bulk_modulus label: Bulk modulus, terbium (WebElements) value: 38.7 unit: GPa scope: material conditions: temperature: not stated method: Value printed on the WebElements physical-properties page status: ground source: webelements-tb where: Elastic properties, row Bulk modulus 38.7 GPa - benchmark: poissons_ratio label: Poisson's ratio, terbium (Wikipedia infobox) value: 0.261 unit: '-' scope: material conditions: temperature: not stated in the infobox method: Value printed in the Wikipedia infobox status: ground source: wikipedia-tb where: Infobox, row Poisson ratio 0.261 - benchmark: poissons_ratio label: Poisson's ratio, terbium (WebElements) value: 0.26 unit: '-' scope: material conditions: temperature: not stated method: Value printed on the WebElements physical-properties page status: ground source: webelements-tb where: Elastic properties, row Poisson's ratio 0.26 (no units) - benchmark: vickers_hardness label: Vickers hardness, terbium (WebElements) value: 863 unit: MPa scope: material conditions: temperature: not stated unit_in_source: 863 MN m-2 method: Value printed on the WebElements physical-properties page, given as MN m-2 (equal to MPa) status: ground note: No canonical name exists for hardness in the property file, so vickers_hardness is a new name and is listed in gaps. source: webelements-tb where: Hardnesses, row Vickers hardness 863 MN m-2 - benchmark: vickers_hardness label: Vickers hardness range, terbium (Wikipedia infobox) value: 450 value_high: 865 unit: MPa scope: material conditions: temperature: not stated in the infobox note_on_range: the infobox gives a range, not a single test value method: Range printed in the Wikipedia infobox status: ground note: The Wikipedia range is 450–865 MPa with no test conditions. vickers_hardness is a new name and is listed in gaps. source: wikipedia-tb where: Infobox, row Vickers hardness 450–865 MPa - benchmark: electrical_resistivity label: Electrical resistivity, terbium alpha polycrystalline form (Wikipedia infobox) value: 1.15 unit: µΩ·m scope: material conditions: temperature: room temperature form: alpha, polycrystalline unit_in_source: 1.150 µΩ⋅m method: Value printed in the Wikipedia infobox, row Electrical resistivity alpha poly 1.150 µΩ⋅m (at r.t.) status: ground source: wikipedia-tb where: Infobox, row Electrical resistivity, α poly 1.150 µΩ⋅m (at r.t.) - benchmark: magnetic_transition_temperature label: Ferromagnetic to helical antiferromagnetic transition, terbium value: 219 unit: K scope: material conditions: transition: ferromagnetic ordering below this temperature, helical antiferromagnetic above it pressure: not stated method: Value printed in the Wikipedia Physical properties section, magnetic ordering paragraph status: ground note: The Wikipedia infobox gives the magnetic ordering as paramagnetic at 300 K and does not print a Curie temperature. magnetic_transition_temperature is a new name and is listed in gaps. source: wikipedia-tb where: Physical properties, paragraph on magnetic ordering, transition at 219 K - benchmark: paramagnetic_transition_temperature label: Helical antiferromagnetic to paramagnetic transition, terbium value: 230 unit: K scope: material conditions: transition: helical antiferromagnetic to disordered paramagnetic pressure: not stated method: Value printed in the Wikipedia Physical properties section, magnetic ordering paragraph status: ground note: paramagnetic_transition_temperature is a new name and is listed in gaps. source: wikipedia-tb where: Physical properties, paragraph on magnetic ordering, paramagnetic state at 230 K corrosion: - environment: Air at room temperature headline: Terbium tarnishes slowly in air and burns readily to form a terbium oxide. effect: WebElements says terbium metal tarnishes slowly in air and burns readily to form a terbium oxide of approximate formula Tb4O7. Wikipedia says the metal is relatively stable in air compared with the more reactive lanthanides, but also that it oxidizes readily in air to a mixed terbium(III,IV) oxide. The two statements disagree in emphasis and are both kept. rating: moderate conditions: temperature: room temperature atmosphere: air source: webelements-tb-chem where: Reaction of terbium with air, paragraph on tarnishing and Tb4O7 - environment: Cold and hot water headline: Terbium reacts slowly with cold water and quite quickly with hot water, releasing hydrogen. effect: WebElements says the metal is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form terbium hydroxide, Tb(OH)3, and hydrogen gas. The Ames SDS says the metal may react with water under fire conditions to liberate flammable hydrogen gas. rating: severe conditions: temperature: cold and hot water form: metal source: webelements-tb-chem where: Reaction of terbium with water, paragraph on cold and hot water - environment: Dilute acids headline: Terbium dissolves readily in dilute sulphuric acid, releasing hydrogen. effect: WebElements says terbium metal dissolves readily in dilute sulphuric acid to form Tb(III) ions and hydrogen gas. The Ames SDS says contact with acids may evolve hydrogen gas. rating: severe conditions: acid: dilute sulphuric acid, and acids in general temperature: not stated source: webelements-tb-chem where: Reaction of terbium with acids, first paragraph - environment: Halogens headline: Terbium reacts with all the halogens to form terbium(III) halides. effect: WebElements says terbium reacts with all the halogens, fluorine, chlorine, bromine and iodine, to form terbium(III) halides. The Ames SDS lists halogens as incompatible materials. rating: severe conditions: atmosphere: halogen gas temperature: not stated source: webelements-tb-chem where: Reaction of terbium with the halogens, first paragraph; Ames SDS section 10, Incompatible Materials risks: hazards: - text: 'PubChem GHS summary (ECHA C&L notifications, 62 company reports): H228 flammable solid in 79 % of notifications, with signal word Danger. 13 of 62 reports say the substance does not meet GHS hazard criteria.' ghs: - H228 source: pubchem-tb where: Safety and Hazards, Hazards Identification, GHS Classification - text: 'Ames Laboratory safety data sheet for terbium (revised January 26, 2016): GHS classification under 29 CFR 1910.1200 is Not classified as hazardous, with no signal word or hazard statements.' ghs: [] source: ames-tb-sds where: Section 2 Hazards Identification, GHS Classification - text: 'Ames SDS: flammable in the form of dust when exposed to heat, sparks or flame. May react with water under fire conditions to liberate flammable hydrogen gas. May emit fumes of terbium oxide under fire conditions.' ghs: [] source: ames-tb-sds where: Section 5 Firefighting Measures, Specific Hazards Arising from the Material - text: 'PubChem hazards summary: little is known about its toxicity. Wikipedia says terbium is poorly studied in toxicology and that few health-based guidance values for safe exposure are available.' ghs: [] source: pubchem-tb where: Safety and Hazards, Hazards Summary; Wikipedia Health and environmental impacts paragraph - text: Wikipedia says no values are established by OSHA or ACGIH at which terbium exposure becomes hazardous. The Ames SDS lists OSHA/PEL and ACGIH/TLV as No exposure limit established. ghs: [] source: wikipedia-tb where: Health and environmental impacts paragraph; Ames SDS section 8, Exposure Limits failure_risks: - mode: Fire in dust, fines and turnings trigger: Terbium dust, fume or fine pieces exposed to heat, sparks or flame, as in grinding, melting or welding consequence: The Ames SDS says the metal is flammable in the form of dust when exposed to heat, sparks or flame, and PubChem records H228 (flammable solid) in 79 % of notifications. severity: high source: ames-tb-sds where: Section 5 Specific Hazards; Section 4 General Measures (grinding, melting or welding create dusts or fumes); PubChem GHS Classification - mode: Hydrogen release on contact with water or acid trigger: Metal in contact with cold or hot water, or with dilute acid, including water applied to a fire consequence: WebElements says the metal reacts quite quickly with hot water and dissolves readily in dilute sulphuric acid, both releasing hydrogen gas. The Ames SDS says water can liberate flammable hydrogen under fire conditions. severity: high source: webelements-tb-chem where: Reaction of terbium with water; Reaction of terbium with acids; Ames SDS section 5 - mode: Surface oxidation in air and moisture trigger: Exposure to air or moisture during storage or handling consequence: The metal tarnishes slowly in air and forms a terbium oxide of approximate formula Tb4O7, and the Ames SDS calls it air and moisture sensitive. severity: moderate source: webelements-tb-chem where: Reaction of terbium with air; Ames SDS section 7, Precautions for Safe Handling - mode: Reaction with halogens trigger: Contact with halogen gas or with halogen-containing materials consequence: The metal reacts with all the halogens to form terbium(III) halides, and the Ames SDS lists halogens as incompatible. severity: moderate source: webelements-tb-chem where: Reaction of terbium with the halogens; Ames SDS section 10, Incompatible Materials side_effects: - text: PubChem lists the adverse effect of terbium as fibrogenic, meaning it induces tissue injury and fibrosis (scarring). No dose or exposure data are given on the record. affects: Workers exposed to terbium dust or fume, for example during grinding, melting or welding source: pubchem-tb where: Toxicity, Toxicological Information, Adverse Effects handling: - text: Store in tightly-closed containers under argon or mineral oil, in a cool, dry area, and protect from moisture (Ames SDS). source: ames-tb-sds where: Section 7 Conditions for Safe Storage - text: Handle in an enclosed, controlled process under dry protective gas such as argon when possible, because the metal is air and moisture sensitive (Ames SDS). source: ames-tb-sds where: Section 7 Precautions for Safe Handling - text: Do not use water on a fire. Use Class D dry powder extinguishing agent (Ames SDS). source: ames-tb-sds where: Section 5 Extinguishing Media and Unsuitable Extinguishing Media - text: Use local exhaust or other engineering controls for dust and fume, wear impermeable gloves and safety glasses, and use a NIOSH approved dust respirator if permissible levels are exceeded (Ames SDS). source: ames-tb-sds where: Section 8 Engineering Controls and Personal Protection mitigations: [] uses: - application: mechanisms device: Terfenol-D magnetostrictive actuator and direct-drive rotary stepper motor (research concept) example: NASA's 1991 report says Tb.3Dy.7Fe2, commercially known as TERFENOL-D, has been used in high power actuators and linear motors, and that NASA researchers were investigating it as the basis of a direct micro-stepping rotary motor. This is a research study, not a flown system. source: nasa-ntrs-1991 where: Abstract of the 1991 Magnetostrictive direct drive motor report (Naik and Dehoff, NTRS 19910013248) - application: optics-and-cameras device: Terbium gallium garnet (TGG) crystal in Faraday rotators and optical isolators example: The 2023 arXiv preprint uses TGG for its broadband isolator study because it is one of the most common crystals for Faraday rotators. TGG is a terbium garnet compound, not the metal. Wikipedia also says terbium-doped garnets are used in optical isolators. source: arxiv-tgg-2023 where: Section on the broadband isolator design (Fig. 1 text, paragraph on TGG); Wikipedia Applications section for the garnet isolator statement - application: electronics-and-chips device: Terbium-activated green phosphor in fluorescent lamps, colour TV tubes and flat-screen monitors example: Wikipedia says most of the world's terbium supply is used in green phosphors. Terbium oxides are used in green phosphors in fluorescent lamps, colour TV tubes and flat screen monitors, and terbium green phosphors are combined with europium phosphors for trichromatic lighting. source: wikipedia-tb where: Applications section, paragraphs on green phosphors supply: - subject: Rare earths (terbium is not reported separately by USGS) abundance: 1.2 mg/kg crust abundance (Wikipedia, Occurrence section) 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: [] recycling: 'USGS: Limited quantities of rare earths were recovered from batteries, permanent magnets, and fluorescent lamps.' substitutes: - 'USGS: Substitutes are available for many applications but generally are less effective.' source: usgs-ree-2026 where: 'World Mine Production and Reserves table, 2025 column: China 270,000 t, United States 51,000 t, Australia 29,000 t, Burma 22,000 t, world total 390,000 t (rounded). Shares are calculated from those printed figures. Reserves: China 44,000,000 t of more than 75,000,000 t world total.' - subject: Rare-earth compounds and metals imported into the United States producers: - country: China share_percent: 71 year: 2024 - country: Malaysia share_percent: 13 year: 2024 - country: Japan share_percent: 5 year: 2024 - country: Estonia share_percent: 5 year: 2024 critical_lists: [] recycling: '' substitutes: [] source: usgs-ree-2026 where: 'Import Sources (2021–24) paragraph: rare-earth compounds and metals, China 71%, Malaysia 13%, Japan 5%, Estonia 5%. The year column shows the end of the 2021 to 2024 range.' - subject: Export controls on terbium producers: [] critical_lists: [] recycling: '' substitutes: [] source: usgs-ree-2026 where: 'Events, Trends, and Issues: In April 2025, China tightened its export controls on rare-earth elements, adding specific controls on alloys, compounds, metals, and oxides of samarium, gadolinium, terbium, dysprosium, lutetium, scandium, and yttrium. The April controls remained in effect, and China began to issue general export licenses to selected exporters.' documents: - title: 'USGS Mineral Commodity Summaries 2026: Rare Earths' type: report url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths.pdf year: 2026 - title: 'Wikipedia: Terbium' type: database url: https://en.wikipedia.org/wiki/Terbium year: 2026 - title: PubChem compound record for terbium (CID 23958), including ECHA C&L Inventory classification type: database url: https://pubchem.ncbi.nlm.nih.gov/compound/23958 year: 2026 - title: Terbium Safety Data Sheet, Ames Laboratory Materials Preparation Center (revised January 26, 2016) type: sds url: https://www.ameslab.gov/sites/default/files/inline-files/65_Terbium_SDS.pdf year: 2016 - title: 'WebElements: Terbium, physical properties (University of Sheffield)' type: database url: https://www.webelements.com/terbium/physics.html - title: 'WebElements: Terbium, chemical reactions (University of Sheffield)' type: database url: https://www.webelements.com/terbium/chemistry.html - title: Magnetostrictive direct drive motor, NASA NTRS 19910013248 (Naik and Dehoff, 1991) type: report url: https://ntrs.nasa.gov/citations/19910013248 year: 1991 - title: Broadband composite nonreciprocal polarization wave plates and optical isolators, arXiv 2305.06431 (Gevorgyan, Rangelov and Vitanov) type: paper url: https://arxiv.org/pdf/2305.06431 year: 2023 gaps: - 'Terbium-specific production: USGS 2026 reports rare earths as one group, so the producer shares above are for all rare earths, not terbium. World output of terbium alone was not found in an opened source.' - 'Critical-mineral listing: the USGS 2025 critical minerals list and the EU critical raw materials list were not opened for terbium, so critical_lists is empty.' - 'Space flight of terbium: no flown terbium metal or flown terbium part was found in the sources read. The NASA item is a 1991 research study of a motor concept. The TGG item is a 2023 simulation preprint and a garnet, not the metal. Environment tags are left empty because no source ties terbium metal to a space environment.' - Terfenol-D magnetostriction (about 2000 ppm, NASA 1991) is for the alloy Tb.3Dy.7Fe2, not terbium metal, so it is not entered as a terbium property. - The TGG Verdet constant is for a garnet crystal, and the text layer of the arXiv paper is garbled at that point, so no Verdet value is entered. - 'Density: WebElements prints 8219 kg m-3 with no temperature, and PubChem prints 8.234 at 25 °C with no unit. Neither is entered. Wikipedia (8.229 at 20 °C) and the Ames SDS (8.230 g/cc) are entered.' - 'Boiling point: Wikipedia gives 3123 °C and the Ames SDS and PubChem give 3230 °C. Both are entered with their sources.' - 'Hardness: vickers_hardness is a new name because the property file has no canonical name for it. Wikipedia gives a range of 450–865 MPa and WebElements gives 863 MN m-2.' - 'Magnetic transitions: 219 K and 230 K are entered under the new names magnetic_transition_temperature and paramagnetic_transition_temperature, because the property file has no canonical name for them and the Curie temperature is not printed for terbium.' - 'Electrical resistivity: WebElements prints 115 × 10-8 Ω m, which is the same as the Wikipedia value of 1.150 µΩ·m, and it is not entered separately.' - 'Mechanical strength: no tensile or yield strength for terbium metal was found in an opened source, and WebElements gives no tensile figures.' - Corrosion data are qualitative (WebElements, Wikipedia, Ames SDS). No measured corrosion rate or weight-gain figure for terbium in air or water was found. Wikipedia says terbium is relatively stable in air and also that it oxidizes readily in air, and both are kept. - 'Hazard data conflict: PubChem records H228 in 79 % of notifications, while the Ames SDS says not classified as hazardous. Both are entered and the form of the metal (dust or solid) is not separated in every source.' - 'Specific heat: the Wikipedia infobox gives 181.904 J/(kg·K) with no temperature, and no temperature was found in another source.' - 'Goodfellow terbium datasheet: the product page returned HTTP 404 and was not read. The PubChem compound web page was blocked by a browser check, so the PubChem REST JSON record was read instead.' - 'Optics Express 2010 (Sun and Jiang, doi 10.1364/OE.18.012191) on terbium-doped fibre Verdet constant: the abstract page returned only a loading page and was not read.' sources: wikipedia-tb: title: Terbium (Wikipedia) url: https://en.wikipedia.org/wiki/Terbium year: 2026 kind: web license: CC BY-SA 4.0 (cited, not reproduced) pubchem-tb: title: 'PubChem compound record: Terbium (CID 23958), including ECHA C&L Inventory classification' id: CAS 7440-27-9 url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23958/JSON kind: database license: PubChem (NCBI), public domain; sections attributed to ECHA and others ames-tb-sds: title: Terbium Safety Data Sheet, Ames Laboratory Materials Preparation Center (revised January 26, 2016) url: https://www.ameslab.gov/sites/default/files/inline-files/65_Terbium_SDS.pdf year: 2016 kind: datasheet license: supplier safety data sheet, cited not reproduced webelements-tb: title: 'WebElements: Terbium, physical properties (University of Sheffield)' url: https://www.webelements.com/terbium/physics.html kind: database license: WebElements, cited not reproduced webelements-tb-chem: title: 'WebElements: Terbium, chemical reactions (University of Sheffield)' url: https://www.webelements.com/terbium/chemistry.html kind: database license: WebElements, cited not reproduced usgs-ree-2026: title: 'Mineral Commodity Summaries 2026: Rare Earths (USGS)' url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths.pdf year: 2026 kind: report license: public domain (USGS) nasa-ntrs-1991: title: Magnetostrictive direct drive motor (NASA NTRS 19910013248, Naik and Dehoff, 1991) url: https://ntrs.nasa.gov/citations/19910013248 year: 1991 kind: report license: NASA public document, cited not reproduced arxiv-tgg-2023: title: Broadband composite nonreciprocal polarization wave plates and optical isolators (arXiv 2305.06431) url: https://arxiv.org/pdf/2305.06431 year: 2023 kind: paper license: arXiv preprint, cited not reproduced license: CC-BY-4.0 updated: '2026-10-26' review: status: draft method: assistant checked_values: 25 unreachable: 3 caveats: 6 note: 'Read by an AI assistant on 2026-10-26 from the pages and PDFs named in each entry. Unreachable: Goodfellow terbium product page (HTTP 404), Optics Express abstract page (loading page only), DTIC magnetostrictive shape-control PDF (not a PDF). Caveats: the physical values come from Wikipedia, WebElements and the Ames SDS; the boiling point and density differ between sources; the hazard classes differ between PubChem and the Ames SDS; supply shares are for all rare earths, not terbium; the magnetic transitions use new property names; the Verdet value for TGG was not entered.' story: risk_groups: - title: For people lead: The sources read say little about human toxicity. The hazard is mainly in the form of the metal, because dust and fumes from grinding, melting or welding can be inhaled. level: 1 verdict: Form-dependent points: - label: Dust and fumes line: Grinding, melting or welding may create dusts or fumes that can be inhaled or contact skin or eyes (Ames SDS, section 4). - label: Classification line: PubChem records H228 (flammable solid) in 79 % of 62 notifications, while the Ames SDS says the metal is not classified as hazardous. - label: Toxicity data line: Wikipedia says terbium is poorly studied in toxicology, and no OSHA or ACGIH exposure limit is established. - title: If it fails lead: 'The sources give four failure routes: a dust fire, hydrogen release with water or acid, tarnishing in air, and reaction with halogens.' points: - label: Fire line: The metal is flammable as dust when exposed to heat, sparks or flame, and water can liberate hydrogen under fire conditions (Ames SDS). - label: Water and acid line: The metal reacts quite quickly with hot water and dissolves readily in dilute sulphuric acid, releasing hydrogen (WebElements). - label: Air line: Terbium tarnishes slowly in air and burns readily to form a terbium oxide of approximate formula Tb4O7 (WebElements). - title: Handling and storage points: - label: Keep it dry line: Store in tightly-closed containers under argon or mineral oil, in a cool, dry area, and protect it from moisture (Ames SDS). - label: Fire agents line: Use a Class D dry powder extinguishing agent. Do not use water (Ames SDS). why: 'Terbium is a rare-earth metal whose best-known roles are light and magnetism. Its strong green emission is the reason most of the world''s terbium goes into green phosphors. Its magnetostriction, as part of the alloy Terfenol-D, drives actuators and sonar. The pure metal is a research material: it is reactive, it is sold in small pieces, and its space-relevant use is through alloys and garnet crystals rather than the metal itself.' uses: - where: Magnetostrictive actuators and motors line: NASA's 1991 report says Terfenol-D, a terbium alloy, has been used in high power actuators and linear motors, and NASA studied it for a direct-drive rotary stepper motor. This is a research concept, not a flown system. - where: Phosphors in lighting and displays line: Terbium oxides are used in green phosphors in fluorescent lamps, colour TV tubes and flat-screen monitors (Wikipedia). - where: Garnet crystals in optical isolators line: Terbium gallium garnet (TGG) is one of the most common crystals for Faraday rotators, according to a 2023 arXiv preprint. TGG is a compound, not the metal. can_do: - label: Melt value: 1356 °C benchmark: melting_point line: The melting point is 1356 °C (Wikipedia), and the Ames SDS prints the same 1356 °C. - label: Weight value: 8.229 g/cm3 benchmark: density line: The density is 8.229 g/cm3 at 20 °C (Wikipedia), and the Ames SDS prints 8.230 g/cc. - label: Heat conduction value: 11.1 W/(m·K) benchmark: thermal_conductivity line: Thermal conductivity is 11.1 W/(m·K) in the Wikipedia infobox, and WebElements prints 11 W/(m·K). - label: Stiffness value: 55.7 GPa benchmark: elastic_modulus line: Young's modulus is 55.7 GPa (Wikipedia), and WebElements prints 56 GPa. - label: Magnetic transition value: 219 K benchmark: magnetic_transition_temperature line: The ferromagnetic ordering lies below 219 K, and the state becomes paramagnetic at 230 K (Wikipedia). compare: Terbium is a dense rare-earth metal at 8.229 g/cm3 (Wikipedia), with a melting point of 1356 °C. Its thermal conductivity of 11.1 W/(m·K) is modest for a metal. It is relatively stable in air compared with the more reactive lanthanides (Wikipedia), but it reacts with hot water and dilute acid. No comparison profile is carried in this file, so the rows below list terbium values only. compare_rows: - label: Density benchmark: density - label: Melting point benchmark: melting_point - label: Thermal conductivity benchmark: thermal_conductivity recipe: line: Terbium is a single-element metal (Tb). Wikipedia says the metal is produced by reducing the anhydrous chloride or fluoride with calcium metal, after ion-exchange separation from the other rare earths. Calcium and tantalum impurities can be removed by vacuum remelting, distillation, amalgam formation or zone melting. parts: - name: Terbium symbol: Tb atoms: 1 atomic_weight: 158.92535 role: The whole material. The Ames SDS lists terbium as the only ingredient of the product. handling: - Store in tightly-closed containers under argon or mineral oil, in a cool, dry area (Ames SDS). - Handle in an enclosed, controlled process under dry gas such as argon when possible (Ames SDS). - Do not use water on a fire. Use a Class D dry powder extinguishing agent (Ames SDS). - If permissible exposure levels are exceeded, use a NIOSH approved dust respirator (Ames SDS). good_for: - 'Green phosphors: most of the world''s terbium supply goes into green phosphors (Wikipedia).' - 'Magnetostrictive actuators: Terfenol-D, a terbium alloy, expands or contracts in a magnetic field (Wikipedia; NASA 1991).' - 'Research: the Ames Laboratory sells terbium for scientific research (Ames SDS).' watch_out: - Dust and fines are flammable, and the Ames SDS says the metal is flammable as dust when exposed to heat, sparks or flame. - Water and dilute acid release hydrogen, and the metal reacts quite quickly with hot water (WebElements). - China's April 2025 export controls cover terbium alloys, compounds, metals and oxides (USGS). - 'Hazard classes differ: PubChem records H228 for most notifications, while the Ames SDS says not classified (PubChem, Ames SDS).' verdict: Terbium is a rare-earth metal whose value lies in its green luminescence and in Terfenol-D, its magnetostrictive alloy. The metal is dense at 8.229 g/cm3 and melts at 1356 °C, and it is flammable as dust and reactive with water and acid, so it needs dry, inert handling. The space evidence is a 1991 NASA study of a Terfenol-D motor concept, not a flown terbium part.