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Antimony
Antimony (Sb, atomic number 51) is a lustrous silvery-white metalloid in Group 15 of the periodic table, classified between metals and non-metals due to its intermediate electrical conductivity and brittle, crystalline nature. With a density of 6.697 g/cm³ and a melting point of 630.63 °C, antimony is considerably denser than most common structural metals and melts at a temperature accessible to conventional steel tooling. Its most stable allotrope has a rhombohedral crystal structure (A7 type) — a layered arrangement of covalently bonded bilayers held together by weak van der Waals forces — which accounts for its easy cleavage, low ductility, and anisotropic physical properties. Pure antimony has a Mohs hardness of 3 and exhibits thermoelectric properties with a positive Seebeck coefficient of approximately +47 µV/K, classifying it as a p-type thermoelectric material.
Antimony's most commercially important property is its synergistic flame-retardant behavior when combined with halogenated compounds. At 2–5 wt% loading as antimony trioxide (Sb₂O₃), it dramatically amplifies the flame-suppression efficiency of chlorine- and bromine-based flame retardants in PVC, polyolefins, and textiles. The mechanism involves gas-phase generation of antimony trihalides (SbX₃), which interrupt combustion chain reactions. This single application accounts for approximately 60% of world antimony consumption. At 1–12 wt%, antimony also hardens lead alloys, improving castability, creep resistance, and cycle life in lead-acid battery grids and babbitt bearing metals.
In the semiconductor and advanced materials domain, antimony is a critical Group V element in narrow-bandgap III-V compound semiconductors. Indium antimonide (InSb, Eg = 0.17 eV) possesses the highest electron mobility of any III-V material (77,000 cm²/V·s at 300 K), enabling mid-infrared photodetectors, Hall sensors, and quantum well transistors. Gallium antimonide (GaSb, Eg = 0.73 eV) underpins thermophotovoltaic cells and cascade laser structures. Sb₂Te₃ is an archetypal topological insulator studied for quantum computing platforms, while Ge₂Sb₂Te₅ (GST) is the active phase-change material in 3D XPoint non-volatile memory.
Goodfellow's range of Antimony (Sb) products, including Antimony Foils, Pellets, Powder, and Sputtering Targets, is essential for research and development laboratories and in many industries. Antimony is widely utilized in semiconductor technology, thermoelectric devices, and battery applications, offering exceptional conductivity and flame-retardant properties. Our high-purity Antimony products, such as Antimony Single Crystal Disks and Thin Films, are tailored for advanced research in materials science, electronics, and energy storage. Known for their versatility, Antimony materials are also critical in applications spanning electronics, metallurgy, and sustainable technologies. With customizable options and precise formulations, Goodfellow provides high-quality Antimony materials to empower innovation for manufacturing and R&D professionals worldwide.
General Properties
| Property | Value | Notes |
|---|---|---|
| Atomic Number | 51 | Group 15 (pnictogen), Period 5; metalloid |
| Atomic Mass | 121.760 u | Two stable isotopes: ¹²¹Sb (57.3%) and ¹²³Sb (42.7%) |
| Density (20 °C) | 6.697 g/cm³ | ~2.5× denser than aluminum; denser than most common metals except lead, copper, and iron |
| Melting Point | 630.63 °C (903.78 K) | Low enough for casting in conventional steel tooling; compatible with lead-alloy processing equipment |
| Boiling Point | 1,587 °C (1,860 K) | Relatively low boiling point for a metal — antimony is moderately volatile; fume extraction required during high-temperature processing |
| Thermal Conductivity | 24.4 W/m·K | Substantially lower than most metals; anisotropic — conductivity varies with crystallographic direction in single-crystal material |
| Specific Heat Capacity | 207 J/kg·K | Low heat capacity relative to light metals; relevant for thermal cycling calculations in thermoelectric module design |
| Coefficient of Thermal Expansion | 11.0 µm/m·°C | Anisotropic in single-crystal form; important for solder joint and thin-film stress calculations |
| Electrical Resistivity | 417 nΩ·m (20 °C) | ~16× higher than copper; semimetallic character — resistivity decreases slightly with temperature in some alloy compositions |
| Crystal Structure | Rhombohedral (A7 type) | Layered structure with alternating covalently bonded bilayers and weak van der Waals interlayer forces; cleaves easily parallel to (001); isostructural with bismuth and arsenic |
| Lattice Parameters | a = 4.307 Å; α = 57.11° | Rhombohedral setting; hexagonal cell: a = 4.307 Å, c = 11.27 Å; used in thin-film epitaxy and XRD reference calculations |
| Reflectivity | ~70–75% (visible) | Lustrous metallic appearance on freshly cleaved surfaces; tarnishes slowly in moist air to form Sb₂O₃ |
Mechanical Properties
| Property | Value | Notes |
|---|---|---|
| Hardness | Mohs 3; ~55 HV | Brittle at room temperature — fractures before plastic deformation; cannot be drawn into wire or rolled into thin foil without special processing |
| Elastic (Young's) Modulus | 55 GPa | Anisotropic; lower than most structural metals; relevant for thin-film stress modeling and MEMS applications |
| Shear Modulus | 20 GPa | Low shear stiffness consistent with layered crystal structure and easy cleavage |
| Poisson's Ratio | 0.25 | Moderate; used in FEA modeling of thermoelectric module stress and thin-film mechanics |
| Fracture Behaviour | Brittle (transgranular) | No measurable ductility at room temperature; cleaves along rhombohedral planes; machining requires carbide tooling and controlled feed rates |
| Compressive Strength | ~80 MPa | Resists compression better than tension; in alloyed form (e.g. Pb-Sb), dramatically increases mechanical performance of the base metal |
Thermal & Environmental Properties
| Property | Value | Notes |
|---|---|---|
| Corrosion Resistance | Good in dry air; moderate in humidity | Forms a thin, adherent Sb₂O₃ passivation layer in air; stable in dilute H₂SO₄ and HCl; attacked by concentrated oxidising acids (HNO₃, hot H₂SO₄) and strong alkalis |
| Oxidation States | –3, 0, +3, +5 | +3 (antimonious) and +5 (antimonic) most commercially relevant; Sb₂O₃ (trivalent) and Sb₂O₅ (pentavalent) are the principal industrial oxides |
| Reactivity with Halogens | Reacts readily above ~100 °C | Forms SbF₃, SbCl₃, SbBr₃; reactions exploited in flame-retardant gas-phase chemistry |
| Toxicology | Toxic — handle with care | Sb and its compounds are toxic by inhalation and ingestion; TLV-TWA 0.5 mg/m³ (ACGIH); classified as possibly carcinogenic (IARC Group 2B) for Sb₂O₃; use appropriate PPE and ventilation |
| Seebeck Coefficient | +47 µV/K (p-type) | Positive coefficient indicates p-type thermoelectric behavior; relevant for Bi-Sb thermoelectric device design at cryogenic temperatures |
Chemical Properties
| Property | Value / Behaviour | Notes |
|---|---|---|
| Surface Oxide | Sb₂O₃ (senarmontite / valentinite) | Two polymorphs: cubic senarmontite (stable below 570 °C) and orthorhombic valentinite (stable above 570 °C); both are the primary passivation and industrial oxide forms |
| Acid Resistance | Resistant to dilute HCl and H₂SO₄ | Dissolves slowly in concentrated HCl; rapidly attacked by hot concentrated H₂SO₄ and HNO₃; resistant to dilute organic acids |
| Alkali Resistance | Attacked by strong alkalis | Dissolves in concentrated NaOH forming antimonates; more alkali-sensitive than arsenic but less so than bismuth |
| Galvanic Behaviour | Noble relative to lead and zinc | When alloyed with lead, Sb acts as a cathodic phase — can accelerate lead corrosion in electrolytic environments if phase separation occurs |
| Identifier | Value |
|---|---|
| Symbol | Sb |
| Atomic Number | 51 |
| CAS Number | 7440-36-0 |
| UN Number | UN2871 (powder) |
| EINECS Number | 231-146-5 |
| Isotope | Type | Notes |
|---|---|---|
| ¹²¹Sb | Stable | 57.21% natural abundance; I = 5/2, NMR-active; used as ¹²¹Sb/¹²³Sb isotope ratio tracer in environmental geochemistry |
| ¹²³Sb | Stable | 42.79% natural abundance; I = 7/2, NMR-active; both stable isotopes used in MC-ICP-MS isotope ratio measurements |
| ¹²⁵Sb | Radioactive | t½ = 2.76 yr (β⁻); gamma emitter used in industrial radiography and as a check source; produced in nuclear reactors |
| ¹²²Sb | Radioactive | t½ = 2.72 days (β⁻/β⁺); produced by neutron activation of ¹²¹Sb; used in neutron activation analysis (NAA) for trace Sb determination |
| ¹²⁴Sb | Radioactive | t½ = 60.2 days (β⁻); strong 1.69 MeV gamma emitter; used as a radiotracer in hydrological studies and as a calibration source |
Scientific & Research Applications
| Use Case | Form Typically Used | Description |
|---|---|---|
| III-V Semiconductor Research | High-purity ingot, sputtering targets, MBE sources | Antimony is an essential Group V element in narrow-bandgap III-V compound semiconductors. InSb (Eg = 0.17 eV) is the highest-electron-mobility III-V semiconductor (77,000 cm²/V·s at 300 K) and is used in mid-IR photodetectors (3–5 µm), Hall sensors, and quantum well transistors. GaSb (Eg = 0.73 eV) underpins thermophotovoltaic cells and cascade laser structures. |
| Topological Insulator Research | Single crystals, thin films | Sb₂Te₃ and Bi₁₋ₓSbₓ alloys are archetypal topological insulators — materials with insulating bulk states but topologically protected metallic surface states — intensively studied for quantum computing (Majorana fermion platforms) and spintronics. Single-crystal Sb substrates with defined (001) orientation are used as growth templates. |
| Thermoelectric Devices | Ingot, powder, sputtering targets | Bi-Sb alloys (x = 0.12–0.15 in Bi₁₋ₓSbₓ) exhibit the highest thermoelectric figure of merit (ZT ~0.5) of any material at cryogenic temperatures (80–200 K), making them the material of choice for Peltier cooling below ambient. |
| Phase-Change Memory (PCM) Research | Sputtering targets, evaporation pellets | Germanium-antimony-tellurium (GST) alloys, particularly Ge₂Sb₂Te₅, are the dominant active material in phase-change memory devices — commercially used in 3D XPoint (Intel Optane) storage. Sb-rich compositions offer faster crystallisation kinetics for high-speed applications. |
| Thin-Film Photovoltaics | Sputtering targets, evaporation sources | Antimony sulfide (Sb₂S₃) and antimony selenide (Sb₂Se₃) are emerging earth-abundant absorber materials for thin-film solar cells, with bandgaps of 1.7 eV and 1.17 eV respectively — well matched to the solar spectrum and of interest as non-toxic alternatives to CdTe and CIGS. |
| Geochemical & Environmental Tracing | High-purity standard solutions, powder | The ¹²¹Sb/¹²³Sb isotope ratio is measurable by MC-ICP-MS and used to trace antimony sources in contaminated soils, mine drainage, and atmospheric particulates. Sb is a regulated environmental contaminant (WHO drinking water guideline: 20 µg/L). |
| Neutron Activation Analysis | High-purity foil, powder | The high neutron capture cross-section of ¹²¹Sb (5.8 barn) and the characteristic gamma energies of ¹²²Sb and ¹²⁴Sb activation products are exploited in instrumental neutron activation analysis (INAA) for trace Sb determination in geological samples, alloys, and archaeological artefacts. |
Industrial & Commercial Applications
| Sector | Alloys / Forms Commonly Used | Description |
|---|---|---|
| Lead-Acid Battery Grids | Pb-Sb alloys (1–12 wt% Sb) | Antimony hardens lead battery grids, improving castability, creep resistance, and cycle life. Modern VRLA batteries have largely replaced Sb with calcium, but Sb-containing alloys remain standard in flooded traction and stationary batteries where deep-cycle durability is paramount. |
| Flame Retardants | Sb₂O₃ powder (ATO) | Antimony trioxide (ATO) is by far the largest end use of antimony globally, consuming ~60% of world production. Used at 2–5 wt% as a synergist with halogenated flame retardants in PVC, polyolefins, textiles, and rubber — gas-phase SbX₃ radicals quench combustion chain reactions. |
| Antifriction / Bearing Alloys | Babbitt metal (Sn-Sb-Cu, Pb-Sb-Sn) | Babbitt metals contain 3–15% Sb to form hard SbSn intermetallic precipitates in a soft Sn or Pb matrix, providing excellent conformability for journal bearings in large turbines, marine engines, and heavy industrial machinery. |
| Glass Manufacturing | Sb₂O₃ (fining agent) | Antimony trioxide is used as a fining (defoaming) agent in specialty optical glass and borosilicate glass. At ~1,400 °C it releases oxygen by reduction to Sb metal, coalescing and removing small bubbles. Being phased out in some applications due to toxicity concerns. |
| Electronics Soldering | Sn-Sb, Pb-Sn-Sb solder alloys | Sn-5Sb solder offers a higher liquidus temperature (~240 °C vs. ~183 °C for eutectic Sn-Pb) and superior creep resistance at elevated temperatures, making it preferred for high-reliability joints in automotive electronics and power modules. |
| Semiconductors (Doping) | High-purity Sb (99.999%+) | Sb is an n-type dopant in germanium and, less commonly, silicon. In III-V device manufacturing, Sb is used as a surfactant during MBE growth of InGaAs and AlGaAs layers to suppress 3D islanding and improve interface quality. |
| Ammunition & Pyrotechnics | Pb-Sb alloy, Sb₂S₃ powder | Antimony sulfide (Sb₂S₃) is a friction-sensitive component used in primer compositions for small-arms ammunition and safety matches. Pb-Sb hardened alloys are used for bullet jackets and shot where hardness and castability are required. |
| Purity | Common Use |
|---|---|
| 95% | General industrial applications — primarily antimony trioxide (ATO) production for flame-retardant synergists in PVC, polyolefins, and textiles, where lower purity is acceptable for bulk chemical processing |
| 99% | Alloys, batteries, and glass manufacturing — suitable for Pb-Sb battery grid hardening, babbitt bearing metals, Sn-Sb solders, and glass fining where controlled impurity levels improve castability and cycle performance |
| 99.99% | Electronic components and semiconductors — used in InSb and GaSb compound synthesis, thermoelectric module fabrication, and sputtering target production where sub-ppm transition metal impurities are required to control carrier concentration |
| 99.999% | Advanced R&D, photonics, and specialty electronics — the standard source for MBE and CVD growth of III-V antimonide heterostructures, phase-change memory (GST) targets, topological insulator research, and single-crystal growth where ppb-level purity is essential |
| Synonym / Alternative Name | Context |
|---|---|
| Stibium | Latin name; origin of the chemical symbol Sb |
| Antimony metal | General commercial and regulatory term |
| Sb | Chemical symbol |
| Regulus of antimony | Historical alchemical term for purified antimony metal |
| Grey antimony | Refers to the common metallic rhombohedral allotrope (most stable form) |
| Black antimony | Amorphous form produced by rapid vapour condensation; metastable; higher reactivity than grey form |
| Yellow antimony | Unstable allotrope formed at very low temperatures; rapidly converts to grey form above –90 °C |
| Antimoine / Antimonio | French and Spanish/Italian language equivalents |