Molybdenum

Molybdenum — Material Page

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Molybdenum (Mo, atomic number 42) is a silvery-white Group 6 refractory transition metal with the fifth-highest melting point of any element (2,623 °C), exceptional high-temperature strength retention, and one of the lowest coefficients of thermal expansion of any structural metal. Its body-centered cubic (BCC) crystal structure, density of 10.28 g/cm³, and Young's modulus of 329 GPa (among the highest of any BCC metal) give molybdenum a combination of stiffness, density, and thermal stability unmatched by most engineering materials in the 1,000–2,500 °C temperature range. Molybdenum is ductile at room temperature in high-purity form — unlike tungsten, which is brittle below its ductile-to-brittle transition temperature (DBTT) — and can be rolled, drawn, and machined. Seven stable isotopes span ⁹²Mo to ¹⁰⁰Mo, including ⁹²Mo and ¹⁰⁰Mo, both candidates for rare double beta decay processes. Molybdenum occurs primarily as molybdenite (MoS₂), and ~80% of global primary production (~300,000 tonnes/year) is as a byproduct of copper porphyry mining — Chile, the US, and China dominate supply. It is classified as a critical raw material by the EU due to supply concentration and essential roles in steel and advanced technology applications.

Molybdenum's largest use — consuming approximately 80% of primary production — is as an alloying addition to steel and superalloys, where even small concentrations (0.1–3 wt% Mo) dramatically improve high-temperature strength, hardenability, creep resistance, and corrosion resistance. Molybdenum is one of the most effective hardenability-increasing elements in steel (hardenability factor ~3–4× that of Mn per unit weight), enabling through-hardening of heavy-section components such as large-diameter shafts, pressure vessel plates, and die blocks. The 300-series and 316-family stainless steels (2–3 wt% Mo) are the standard "marine grade" stainless — the Mo addition improves resistance to pitting and crevice corrosion in chloride environments by stabilizing the passive film and raising the pitting potential. High-speed steels (M-grade: M2 = Fe-0.85C-6W-5Mo-4Cr-2V, the most widely produced HSS grade) use Mo-W synergy to achieve red hardness (maintaining >60 HRC at 600 °C) for cutting tools. Nickel superalloys for gas turbine blades (IN-718, Hastelloy X, Inconel 625) incorporate 3–9 wt% Mo for solid-solution strengthening and oxidation resistance at turbine inlet temperatures above 1,000 °C; Mo additions to cobalt superalloys (Haynes 25) provide similar benefits.

Beyond steel alloying, molybdenum's refractory properties, favorable electrical characteristics, and unique chemistry in sulfide and oxide compounds give it critical roles in thin-film electronics, industrial catalysis, nuclear medicine, and as a structural material for high-temperature furnaces and vacuum systems. Molybdenum thin films and sputtering targets are used in CIGS thin-film solar cells as the back contact (Mo layer on soda-lime glass provides ohmic contact and Na-ion diffusion pathway for CIGS efficiency optimization), in flat-panel display TFT metallization (Mo/Al/Mo gate and source/drain stacks in IGZO and a-Si TFTs), and in semiconductor diffusion barrier research. MoS₂ — the natural ore of molybdenum and the world's most widely used solid lubricant — has reemerged as a two-dimensional material of intense scientific interest: monolayer MoS₂ is a direct-bandgap semiconductor (Eg = 1.8 eV) with valley-selective optical properties, making it the leading chalcogenide for valleytronics and 2D transistor research. ⁹⁹Mo (t½ = 66 hr), produced by neutron fission of ²³⁵U or neutron activation of ⁹⁸Mo, is the parent isotope of the ⁹⁹Mo/⁹⁹ᵐTc generator — the source of ⁹⁹ᵐTc (technetium-99m), the most widely used radioisotope in nuclear medicine diagnostic imaging (~80% of all nuclear medicine procedures globally).

General Properties

Property	Value	Notes
Atomic Number	42	Group 6, Period 5; transition metal; 4d⁵5s¹ electron configuration — half-filled 4d shell gives Mo a similar electronic structure to Cr (3d⁵4s¹) and a wide range of oxidation states (+2 to +6); sits above tungsten (74) in the same group; seven stable isotopes, one of the most isotopically diverse elements
Atomic Mass	95.95 u	Seven stable isotopes spanning ⁹²Mo to ¹⁰⁰Mo with no single dominant isotope; ⁹⁸Mo is most abundant (24.39%); the wide isotope spread enables IDMS measurements for Mo geochemistry and enables Mo isotope ratio (δ⁹⁸Mo, δ⁹⁷Mo) MC-ICP-MS measurements used as redox proxies in ancient ocean chemistry and ore deposit formation studies; ⁹⁸Mo can be activated to ⁹⁹Mo by reactor neutron capture
Density (20 °C)	10.28 g/cm³	High density — approximately 1.3× iron, comparable to silver; lower than tungsten (19.25 g/cm³), rhenium (21.02 g/cm³), and osmium (22.59 g/cm³); the density/melting point combination makes Mo the highest-melting-point metal with density below ~12 g/cm³, giving it a unique role in applications requiring refractory properties without the extreme mass penalty of W or Re components
Melting Point	2,623 °C (2,896 K)	Fifth-highest melting point of any element (after W, Re, Os, Ta); approximately 1,000 °C above nickel and 1,085 °C above iron; Mo retains useful strength to ~1,900 °C in inert atmosphere — far above the useful temperature limit of most competing refractory metals and ceramics; Mo melts well above the operating temperature of standard electric arc furnaces (~1,700 °C), requiring electron beam melting or powder metallurgy (sintering + hot working) for fabrication
Boiling Point	4,639 °C (4,912 K)	One of the highest boiling points of any element; Mo vapor pressure at 1,600 °C is ~10⁻⁸ Pa — negligible for vacuum applications; at 2,000 °C it is ~10⁻⁴ Pa, still very low; this minimal vapor pressure makes Mo an ideal vacuum furnace structural material where metal evaporation would contaminate processed materials or degrade insulation
Thermal Conductivity	138 W/m·K (25 °C)	High thermal conductivity for a refractory metal — substantially higher than tungsten (173 W/m·K at 25 °C), much higher than TiN (~20 W/m·K), ZrO₂ (~2 W/m·K), or carbon steel (~50 W/m·K); Mo's high conductivity enables efficient heat spreading in power electronics substrates (Mo heat sinks, Mo-Cu composites), uniform temperature distribution in furnace heating elements, and effective thermal management in high-power laser mirrors
Electrical Resistivity	53.4 nΩ·m (20 °C)	Low resistivity for a refractory metal — approximately 3.2× copper (16.8 nΩ·m) but much lower than tungsten (53 nΩ·m, similar); sufficiently low for use in thin-film metallization (TFT gate metals, CIGS back contact), high-current vacuum feedthroughs, and resistance heating elements where lower resistivity means less wasted heat in leads vs. the working element; resistivity increases linearly with temperature (TCR ~4.35 × 10⁻³/°C)
Crystal Structure	BCC; a = 3.147 Å (room temperature)	BCC structure stable from RT to melting; no allotropic transformations — unlike tungsten and iron; the BCC structure enables room-temperature ductility in high-purity Mo (unlike the BCC W which is brittle below DBTT ~400 °C); Mo DBTT (~−20 to +100 °C depending on purity and prior processing) is much lower than W, allowing Mo to be mechanically worked at or near room temperature in reasonably pure form; grain boundary segregation of O, P, S, and C dramatically raises the DBTT

Mechanical Properties

Property	Value	Notes
Hardness	Mohs ~5.5; ~1,530 MPa Vickers (annealed pure Mo)	Moderately hard in the annealed condition — can be machined with carbide tools; work hardening is significant, and cold-drawn Mo wire is substantially harder; ODS (oxide-dispersion-strengthened) Mo alloys (Mo-La₂O₃, TZM: Mo-0.5Ti-0.08Zr-0.025C) achieve 200–350 HV, roughly doubling the hardness of pure Mo through dispersoid pinning of grain boundaries and dislocations
Elastic (Young's) Modulus	329 GPa	One of the highest elastic moduli of any metal — 1.56× iron (211 GPa) and 4.7× aluminum (70 GPa); the high modulus makes Mo an excellent structural material where dimensional stability under load is critical — precision grinding mandrels, die-casting tooling, and high-temperature furnace fixtures; the modulus decreases to ~310 GPa at 500 °C and ~270 GPa at 1,000 °C, still substantially higher than most competing materials at these temperatures
Poisson's Ratio	0.31	Typical BCC metal Poisson's ratio; used in stress analysis of Mo structural components and thin-film residual stress calculations; the high modulus and moderate Poisson's ratio give Mo a bulk modulus of ~230 GPa and shear modulus of ~126 GPa — among the highest of any common metal
Tensile Strength	~550 MPa (annealed rod); ~700–1,200 MPa (cold-worked)	Good tensile strength at RT, maintained to exceptional levels at high temperature: ~500 MPa at 500 °C, ~300 MPa at 1,000 °C, ~100 MPa at 1,500 °C — far exceeding nickel superalloys (<100 MPa at 1,100 °C) and steel (<50 MPa at 1,000 °C); TZM alloy (Mo-0.5Ti-0.08Zr-0.025C) extends this to ~700 MPa at 1,000 °C through dispersoid strengthening

Thermal & Chemical Properties

Property	Value / Behavior	Notes
Oxidation Behavior	Forms volatile MoO₃ above ~500 °C in air; excellent resistance below 400 °C	Molybdenum's critical oxidation limitation is the volatility of MoO₃ (mp 795 °C, significant vapor pressure above ~500 °C) — unlike W, which forms a protective WO₃ scale, Mo undergoes "pest" oxidation above ~500 °C in air with accelerating mass loss due to MoO₃ volatilization; molybdenum components for high-temperature use require inert atmosphere (Ar, H₂, or vacuum) protection; MoSi₂ coatings and Mo-Re alloy additions improve oxidation resistance; below ~400 °C in dry air, Mo is essentially unaffected
Corrosion Resistance	Excellent in mineral acids (HCl, H₂SO₄, HF); attacked by HNO₃ and oxidizing acids	Mo is resistant to HCl, dilute H₂SO₄, dilute HF, and many organic acids at room temperature — making it the standard electrode material for electrochemical cells with aggressive electrolytes; resistant to liquid sulfur, sulfide melts, and molten glass up to ~1,500 °C; attacked by hot concentrated HNO₃, hot H₂SO₄, and mixtures of HNO₃/H₂SO₄; resistant to liquid sodium and potassium up to ~700 °C; excellent in vacuum and inert atmosphere to its melting point
Coefficient of Thermal Expansion	4.8 µm/m·°C (20–100 °C)	One of the lowest CTEs of any structural metal — comparable to Fe-Ni Invar alloys (~1.2 µm/m·°C) but achievable in pure metal form without special composition; the low CTE closely matches silicon (~2.6 µm/m·°C) and alumina (~7 µm/m·°C), making Mo the preferred substrate and heat spreader for high-power electronics where CTE mismatch would cause solder joint fatigue or die cracking; Mo-Cu composites (10–40% Cu by volume) tailor CTE between 6–12 µm/m·°C for matched thermal management substrates
Oxidation States & Key Compounds	+2 to +6; dominant: MoO₃ (+6), MoS₂ (+4), MoO₄²⁻ (+6)	MoO₃ is the industrial starting material for most Mo chemistry (from molybdenite roasting); molybdate (MoO₄²⁻) is the form of Mo in biological systems (cofactor in nitrogenase, xanthine oxidase, sulfite oxidase); MoS₂ is the dominant ore mineral and the standard solid lubricant (lamellar structure, low shear between S-Mo-S layers, stable to ~400 °C in air, ~800 °C in vacuum); Mo carbides (Mo₂C, MoC) are hard, catalytically active materials used as platinum-group-metal substitutes for hydrodesulfurization and hydrogen evolution catalysis

Identifier	Value
Symbol	Mo
Atomic Number	42
CAS Number	7439-98-7
UN Number	Not classified (bulk metal); UN3089 applies to Mo powder
EINECS Number	231-107-2

Isotope	Type	Notes
⁹²Mo	Stable	14.53% natural abundance; I = 0; candidate for double electron capture decay to ⁹²Zr (t½ >10²⁰ yr, not yet observed); used as an enriched IDMS spike for Mo concentration measurements; ⁹²Mo is one of the p-process nuclides thought to be produced by photodisintegration in supernova envelopes
⁹⁴Mo	Stable	9.15% natural abundance; I = 0; p-process nuclide; used in enriched isotope studies; ⁹⁴Mo(p,n)⁹⁴Tc reaction has been studied for production of the short-lived PET isotope ⁹⁴ᵐTc (t½ = 52 min)
⁹⁵Mo	Stable	15.84% natural abundance; I = 5/2, NMR-active; ⁹⁵Mo NMR (along with ⁹⁷Mo) is used to characterize Mo coordination in catalysts, polyoxomolybdates, Mo enzymes (molybdopterin cofactor), and MoS₂-based materials; thermal neutron capture cross-section ~13.4 barn
⁹⁶Mo	Stable	16.67% natural abundance; I = 0; the second most abundant Mo isotope; double beta decay candidate to ⁹⁶Ru (Q = 3.35 MeV, t½ >10²⁰ yr, experimentally constrained but not definitively observed at current sensitivity); studied in solar neutrino detection proposals
⁹⁷Mo	Stable	9.60% natural abundance; I = 5/2, NMR-active; ⁹⁷Mo NMR used in parallel with ⁹⁵Mo NMR for structural characterization (slightly different quadrupole moment); δ⁹⁷Mo isotope ratios (MC-ICP-MS) are used as palaeoredox proxies — Mo fractionates between oxic and anoxic marine sediments, enabling reconstruction of ancient ocean oxygenation and biological Mo utilization over geological history
⁹⁸Mo	Stable	24.39% natural abundance — the most abundant Mo isotope; I = 0; ⁹⁸Mo(n,γ)⁹⁹Mo reaction (thermal neutron cross-section ~0.13 barn) is used for reactor-based production of ⁹⁹Mo (the ⁹⁹Mo/⁹⁹ᵐTc generator parent); enriched ⁹⁸Mo targets are used for high-specific-activity ⁹⁹Mo production in research reactors where the neutron flux is insufficient to achieve high yield from natural Mo
¹⁰⁰Mo	Stable*	9.82% natural abundance; I = 0; two-neutrino double beta decay to ¹⁰⁰Ru has been measured (t½ = 7.1 × 10¹⁸ yr); candidate for neutrinoless double beta decay search (0νββ, Q = 3.034 MeV) — the NEMO-3 and SuperNEMO experiments use enriched ¹⁰⁰Mo foils to search for lepton number violation and Majorana neutrino mass; the relatively high Q-value (3.034 MeV) is favorable for 0νββ experiments as it places the signal above most natural radioactivity backgrounds
⁹⁹Mo	Radioactive	t½ = 65.94 hr (β⁻); the most important Mo radioisotope; produced primarily by thermal neutron fission of ²³⁵U (fission yield ~6.1%) in nuclear reactors at dedicated high-flux facilities (BR2 Belgium, NRU Canada, Safari-1 South Africa, HFR Netherlands); parent of the ⁹⁹Mo/⁹⁹ᵐTc generator (cow) — ⁹⁹ᵐTc (t½ = 6.01 hr, 140.5 keV gamma) is eluted daily and used in ~85% of all nuclear medicine diagnostic imaging procedures worldwide (bone scans, myocardial perfusion, sentinel lymph node, renal, pulmonary, thyroid); ⁹⁹Mo supply security is a critical global public health infrastructure concern — disruption of the small number of producer reactors causes immediate shortages of ⁹⁹ᵐTc for patient imaging

Scientific & Research Applications

Use Case	Form Typically Used	Description
CIGS Solar Cell Back Contact & Thin-Film Research	Mo sputtering targets (99.95–99.99%), Mo foil	Mo is the standard back contact layer (~500–1,000 nm) in CIGS (Cu(In,Ga)Se₂) and CdTe thin-film solar cells — deposited by DC magnetron sputtering onto soda-lime glass. The Mo/CIGS interface forms a MoSe₂ interlayer that provides ohmic contact; the Mo layer also serves as a Na-ion diffusion pathway from the SLG substrate into the CIGS absorber, enhancing carrier concentration and cell efficiency (~0.3% absolute efficiency improvement from Na). Research focuses on Mo bilayer optimization (dense/porous Mo stacks for stress management and Na flux control) and Mo-on-flexible-substrate deposition for roll-to-roll CIGS manufacturing.
Flat-Panel Display TFT Metallization	Mo sputtering targets (99.95–99.99%), Mo-Nb/Mo-W alloy targets	Mo and Mo alloy films (Mo/Al/Mo tri-layer, Mo-Nb, Mo-W) are used as gate metal and source/drain contact layers in thin-film transistors (TFTs) for LCD and OLED flat-panel displays — valued for low resistivity (~75 nΩ·m thin film), good adhesion to glass, compatibility with wet-etch patterning (H₃PO₄/HNO₃/acetic acid), and resistance to hillock formation during processing. Mo-Nb alloys (5–10% Nb) improve etch uniformity; Mo-W alloys improve high-temperature stability for oxide TFT backplane processing temperatures above 400 °C.
High-Temperature Furnace Components	Mo plate, rod, crucible, heating element (99.95%+)	Molybdenum is the preferred structural and heating element material for vacuum and inert-atmosphere furnaces operating at 1,200–2,000 °C — used in hot zones of sapphire crystal growth furnaces (Czochralski/HEM), SiC crystal growth reactors (PVT method), rare earth magnet sintering furnaces, and UHV ultra-high-temperature annealing equipment. Mo's combination of high-temperature strength, low vapor pressure, and acceptable electrical resistivity for resistive heating makes it the material of choice where graphite would contaminate oxide or carbide-sensitive processes. Mo crucibles are standard for high-temperature melting of rare earth metals, actinides, and refractory oxides.
X-ray Anode Targets	Mo foil and rod (99.95–99.99%), Mo/W composite anodes	Molybdenum X-ray tube anodes are used in mammography X-ray systems — Mo's characteristic X-ray emission lines at 17.5 keV (Kα) and 19.6 keV (Kβ) fall in the optimal energy range for soft tissue contrast in breast imaging (below 20 keV), achieving better image contrast for microcalcifications and masses than the 59 keV emission of W anodes used in general radiography. Rotating Mo anodes (or Mo/Rh dual-track anodes for dense breast tissue) are standard in mammography tubes. Mo anodes are also used in analytical X-ray fluorescence (XRF) systems for lighter element analysis.
Hydrodesulfurization (HDS) Catalysis Research	MoO₃/Al₂O₃ → MoS₂/Al₂O₃ (sulfided catalyst); Mo carbide powder	Supported MoS₂ catalysts (typically MoO₃/Al₂O₃ pre-sulfided to MoS₂/Al₂O₃, promoted with Co or Ni — CoMo or NiMo catalysts) are the industrial standard for hydrodesulfurization (HDS) of petroleum fractions — removing thiophenes, dibenzothiophenes, and other sulfur compounds from diesel, gasoline, and jet fuel to meet increasingly stringent sulfur emission regulations (<15 ppm sulfur for ultra-low-sulfur diesel). HDS is the largest application of heterogeneous catalysis by volume. Mo carbides (Mo₂C, MoC) are studied as platinum-group-metal substitutes for hydrogen evolution (HER) and nitrogen reduction (NRR) catalysis.
Neutron Scattering Sample Environments	Mo rod, plate, wire for sample holders and furnace components	Molybdenum is a preferred construction material for neutron scattering sample environment equipment — high-temperature furnaces (to 2,000 °C), pressure cells, and sample holders — because its low neutron absorption cross-section (~2.5 barn average over natural Mo) minimizes sample environment background, its high-temperature strength maintains structural integrity during experiments, and its low vapor pressure ensures clean vacuum conditions in scattering chambers. Mo furnaces at ILL (Grenoble), ISIS (Oxfordshire), and SNS (Oak Ridge) enable in situ neutron diffraction during high-temperature reactions.

Industrial & Commercial Applications

Sector	Form / Grade Used	Description
Steel & Superalloy Alloying	Ferromolybdenum (60–70% Mo), MoO₃ technical grade, Mo metal powder	Molybdenum is added to virtually all stainless steels (316/316L: 2–3% Mo for marine and pharmaceutical use), high-speed steels (M2: 5% Mo), die steels (H13: 1.5% Mo), pressure vessel steels (ASTM A387 Gr. 22: 0.87–1.13% Mo), and nickel superalloys (Inconel 625, Hastelloy X, IN-718). Key effects: hardenability (very strong), creep resistance (solid solution and precipitation), pitting corrosion resistance (Mo in passive film raises pitting potential), and tempering resistance (Mo carbides prevent softening on tempering). Approximately 80% of primary Mo production is consumed in steel and superalloy alloying.
Electrodes for EDM & Glass Melting	Mo rod and tube (99.95%), Mo-lanthanum oxide (ML, Mo-0.3%La₂O₃)	Mo electrodes are used in electrical discharge machining (EDM) wire and sinker electrodes where high melting point, dimensional stability, and low erosion rate are required for precision hole drilling in hardened steels and cemented carbides. Mo electrodes for glass melting furnaces (borosilicate, specialty optical glass, glass fiber) provide corrosion resistance against molten glass at 1,200–1,500 °C while maintaining structural integrity — Mo dissolves negligibly in most glass melts, unlike Pt electrodes which are too expensive for large-scale glass melting applications.
MoS₂ Solid Lubricant	MoS₂ powder (technical grade, <2 µm), MoS₂ coating (sputtered or burnished)	Molybdenum disulfide (MoS₂) is the world's most widely used solid lubricant — its lamellar hexagonal structure (S-Mo-S layers held together by weak van der Waals forces) provides extremely low friction (µ ≈ 0.02–0.05 in vacuum and inert gas) without liquid lubricant. MoS₂ coatings (deposited by sputtering, burnishing, or in epoxy binders) are standard for spacecraft bearings and mechanisms (functioning in vacuum where liquid lubricants evaporate), aerospace fasteners (prevents galling in stainless steel threads), and automotive transmission components. MoS₂ in engine oil additive packages (MoDTC friction modifier) reduces boundary lubrication friction by up to 40%.
⁹⁹Mo/⁹⁹ᵐTc Radioisotope Production	Enriched ²³⁵U targets (fission route); ⁹⁸Mo-enriched targets (activation route)	⁹⁹Mo is the parent of ⁹⁹ᵐTc (t½ = 6.01 hr), the most widely used diagnostic radioisotope in nuclear medicine — used in approximately 40 million patient procedures per year globally for bone scans, myocardial perfusion imaging (stress/rest cardiac), renal function studies, pulmonary ventilation/perfusion, and sentinel lymph node mapping. The ⁹⁹Mo/⁹⁹ᵐTc generator (alumina column chromatography, eluted with saline) must be replaced weekly due to ⁹⁹Mo decay; the entire global supply chain depends on a handful of dedicated high-flux reactors (BR2, NRU, HFR, Safari-1) producing fission-yield ⁹⁹Mo, creating significant supply vulnerability.
Aerospace Refractory Components	Mo alloys (TZM: Mo-0.5Ti-0.08Zr-0.025C; ML: Mo-La₂O₃), Mo-Re alloys	TZM (Mo-0.5%Ti-0.08%Zr-0.025%C) is the workhorse high-strength Mo alloy — its dispersed carbide phases (Mo₂C, TiC) pin grain boundaries, maintaining high-temperature strength to ~1,400 °C and raising the recrystallization temperature by ~200 °C vs. pure Mo. Used in aircraft structural components exposed to aerodynamic heating, nozzle inserts for liquid rocket engines (where Mo's erosion resistance and high-temperature strength are critical), re-entry vehicle throat liners, and X-ray tube rotating anodes. Mo-Re alloys (41–47.5% Re) are used where enhanced ductility at low temperatures and superior high-temperature strength beyond TZM capability are required (space nuclear power systems, extremely high-temperature thermocouples).
Mo-Cu Thermal Management Substrates	Mo-Cu composites (10–30% Cu by volume), Mo heat spreader plates	Mo-Cu composites (10–30% Cu infiltrated into Mo powder compacts) provide tunable CTE (6–10 µm/m·°C, matching AlN, Al₂O₃, and Si) combined with high thermal conductivity (160–200 W/m·K) for power electronics thermal management — used as heat spreaders and submounts for high-power GaN RF transistors, IGBT modules, and high-brightness LED arrays. Pure Mo plates are used as heat spreaders in microwave power modules (traveling wave tube amplifiers, TWTAs) where the CTE match to semiconductor die is more critical than thermal conductivity. Mo-Cu is also the standard backing plate material for sputtering target assemblies requiring both thermal conductivity and dimensional stability.

Purity	Main Use
99.8%	Industrial-grade molybdenum for furnace components, electrodes, glass melting hardware, and general-purpose alloy additions — where sub-0.2% impurities (primarily Fe, Ni, Cr, Si, C) are acceptable and full refractory performance at elevated temperature is the primary requirement
99.9%	High-purity material for demanding metallurgical and coating applications — TZM and ML alloy sintering feedstock, Mo crucibles for rare earth metal melting, and EDM electrodes where consistent erosion behavior requires low impurity variation
99.95%	Research-grade molybdenum for electronics and scientific instruments — the standard purity for CIGS back contact sputtering targets, flat-panel display TFT metallization targets, X-ray tube anode discs, vacuum furnace heating elements, and neutron scattering sample environments
99.98%	Ultra-high purity for semiconductor applications and sensitive vacuum environments — Mo sputtering targets for advanced logic and memory thin-film metallization, Mo diffusion barrier research, and UHV surface science studies where sub-200 ppm total metallic impurities are required
99.999% (5N)	Electronic-grade molybdenum for advanced microelectronics and specialized research — the highest-purity form for fundamental studies of Mo electronic structure and surface chemistry, zone-refined single crystal growth for Fermi surface measurements, and isotopically enriched Mo (⁹⁸Mo, ¹⁰⁰Mo) targets for radioisotope production and neutrinoless double beta decay experiments

Synonym / Alternative Name	Context
Mo	Chemical symbol; from the Greek molybdos (μόλυβδος), meaning lead — molybdenite (MoS₂) was historically confused with graphite and lead-bearing minerals (galena, PbS) because all three leave gray marks on paper; the element was distinguished from lead compounds by Carl Wilhelm Scheele in 1778 and first isolated by Peter Jacob Hjelm in 1781
Molybdenum metal	Standard commercial and regulatory designation for the elemental form; used in trade documentation for Mo powder, sintered Mo plate/rod, and Mo sputtering targets; distinguished from ferromolybdenum (FeMo, the dominant steel alloying form) and molybdenum compounds (MoO₃, MoS₂, ammonium molybdate, ferromolybdenum) in supply chain and customs classification
Elemental molybdenum	Scientific term distinguishing pure Mo metal from molybdenum compounds (MoO₃, MoS₂, MoO₄²⁻, molybdopterin, MoC, MoSi₂, Mo₂C) in chemistry and materials literature; used in surface science, thin-film deposition, and electrochemistry literature
Ferromolybdenum (FeMo)	Fe-Mo alloy (60–75% Mo, balance Fe) produced by aluminothermic reduction of MoO₃; the principal commercial form in which Mo is added to steel — not pure Mo, but the most commonly encountered Mo-bearing material in steelmaking; produced to ASTM A132 standard; listed here as the dominant industrial Mo-bearing product
TZM alloy	Mo-0.5Ti-0.08Zr-0.025C (wt%) — the most widely used high-strength molybdenum alloy; sintered by powder metallurgy then hot-worked; provides ~50% higher high-temperature strength than pure Mo through TiC/ZrC dispersoid grain boundary pinning; the standard Mo alloy for elevated-temperature structural applications in aerospace, nuclear, and high-temperature furnace engineering; "TZM" stands for Titanium-Zirconium-Molybdenum

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