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About Hafnium

Hafnium Bohr

In 1869, Dmitri Mendeleev’s periodic table predicted the existence of an element with 72 protons that would be chemically similar to zirconium . Though Henry Moseley and Niels Bohr’s subsequent theoretical models of the elements supported this prediction, it was not until 1923 that Georg von Hevesy and Dirk Coster provided the first empirical evidence of the elusive element 72, the penultimate element with stable isotopes to be discovered (followed by rhenium two years later). While working at the Bohr Institute of Theoretical Physics in Copenhagen, the two chemists identified the new element via x-ray spectroscopy analysis of a zirconium ore and named it "hafnium" after Hafnia, the Latin name for Copenhagen.

True to Mendeleev’s theory, Hafnium is extremely similar to zirconium; with nearly identical atomic radii, the two always occur together in nature in a continuous solid-solution and are two of the most difficult elements to separate. Primarily zirconium-based minerals typically contain 1-3% hafnium, the most common (and the subject of Coster and von Hevesy’s experiment) being zircon (zirconium silicate) with up to 4% hafnium by content. Other such zirconium-rich minerals include eudialyte, thortveitite, cyrtolite, armstrongite, alvite, and hafnon; the two elements can also be found in minerals such as the titanium ores ilmenite and rutile. Hafnium metal is primarily obtained as a byproduct of producing high-purity nuclear grade zirconium metal. The metals are typically chemically separated via a liquid-liquid extraction process that utilizing the slightly different solubilities of the two metals’ salts.

In its elemental form, hafnium is a ductile gray metal with a brilliantly lustrous silver sheen. Exposure to air causes the metal to form an impenetrable oxide film on its surface which lends the metal an extremely high resistance to corrosion and attack by most acids and alkalis. Because Hafnium’s melting point is high among its fellow transition metals, it is occasionally classified as a refractory metal. Like many other metals, hafnium as a fine powder is pyrophoric, meaning that it can ignite in air; for this reason, it is considered a hazardous material despite being non-toxic to humans. Thought hafnium shares many chemical and physical properties with zirconium, the two metals differ significantly in their densities (hafnium being roughly twice as dense) and their nuclear properties. Hafnium is an excellent neutron absorber with a high thermal neutron cross section, about 600 times that of zirconium, and one of its primary commercial uses is in control rods of nuclear reactors. It has also been used to enhance radiotherapy in the treatment of cancer.

Compound and alloy forms of hafnium are notable for their refractory properties. The melting points of several hafnium compounds are unparalleled within their respective groups: hafnium nitride’s (3310 °C) is the highest of any nitride, hafnium carbide’s (3890 °C) is the highest of any known binary compound, and tantalum hafnium carbide’s (4215 °C) is the single highest of any known compound. Thus, forms of hafnium are frequently employed in high-temperature environments as components of furnace linings, ceramics, rocket thrusters and jet engines for the aerospace industry, nozzle tips for plasma arc cutting, and wear resistant coatings. High performance superalloys typically contain hafnium in combination with metals like titanium, tungsten, and niobium; the metal improves creep ductility, strengthens grain boundaries, and increases corrosion resistance. Other applications for hafnium include serving as an oxygen and nitrogen “getter” in vacuum tubes and incandescent lighting, in geological dating (as isotopes), and in organic catalysis. Additionally, compounds like hafnium oxide and hafnium silicate have shown great promise as high-k dielectric materials that increase efficiency of semiconductor devices such as integrated circuits and transistors in the field of advanced microelectronics.

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There are relatively few technical uses for hafnium and, due to its ability as a nuclear "getter" or absorber of neutrons, much of the hafnium that is produced is used in control rods for nuclear reactors. Hafnium is also used in iron, titanium, niobium, tantalum, and other alloys. Hafnium is replacing polysilicon as the principle gate or electrode material in metal-oxide semiconductor field effect transistors (MOSFETs), which are the basis for all modern semiconductors. As semiconductors get smaller, the limiting factor in further size reduction has been the ability of the silicon dioxide gate to perform below 10 angstroms where leakage occurs. High Purity (99.999%) Hafnium (Hf) Sputtering TargetRecent research has been devoted to the development of high-k materials which can function as a di-electric barrier or gate with lower leakage. Using hafnium based alloys as this di-electric gate has allowed for the development of MOSFET gates smaller than 10 angstroms.This allows for further size reduction, reduced switching power requirements and improved performance. High Purity (99.999%) Hafnium Oxide (HfO2) PowderHafnium is available as metal and compounds with purities from 99% to 99.999% (ACS grade to ultra-high purity). Elemental or metallic forms of hafnium include pellets, rod, wire and granules for evaporation source material purposes. Hafnium nanomaterials provide ultra-high surface area which nanotechnology research and recent experiments demonstrate function to create new and unique properties and benefits. Hafnium oxide is available in powder and dense pellet form for such uses as optical coating and thin film applications. Oxides tend to be insoluble. Fluorides are another insoluble form for uses in which oxygen is undesirable such as metallurgy, chemical and physical vapor deposition and in some optical coatings. Hafnium is also available in soluble forms including chloride, nitrate and acetate. These compounds can be manufactured as solutions at specified stoichiometries.

Hafnium Properties

Hafnium(Hf) atomic and molecular weight, atomic number and elemental symbol Hafnium is a Block D, Group 4, Period 6 element. The number of electrons in each of Hafnium's shells is 2, 8, 18, 32, 10, 2 and its electronic configuration is [Xe] 4f14 5d2 6s2. Hafnium Bohr ModelThe hafnium atom has a radius of 156.4.pm and its Van der Waals radius is 200.pm. Elemental HafniumIn its elemental form, CAS 7440-58-6, hafnium has a steel gray appearance. Hafnium does not exist as a free element in nature. It is found in zirconium compounds such as zircon (ZrSiO4). Hafnium was first predicted by Dmitri Mendeleev in 1869 but it was not until 1922 that it was first isolated Dirk Coster and George de Hevesy.

Symbol: Hf
Atomic Number: 72
Atomic Weight: 178.49
Element Category: transition metal
Group, Period, Block: 4, 6, d
Color: silvery/ gray steel
Other Names: Afnio, Háfnio, Hafnio
Melting Point: 2233 °C, 4051 °F, 2506 K
Boiling Point: 4603 °C,8317 °F, 4876 K
Density: 13.31 kg·cm3
Liquid Density @ Melting Point: 12 g·cm3
Density @ 20°C: 13.2 g/cm3
Density of Solid: 13310 kg·m3
Specific Heat: 0.14 (kJ/kg K)
Superconductivity Temperature: 0.128 [or -273.022 °C (-459.44 °F)] K
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): 25.5
Heat of Vaporization (kJ·mol-1): 570.7
Heat of Atomization (kJ·mol-1): 618.9
Thermal Conductivity: 23.0 W·m-1·K-1
Thermal Expansion: (25 °C) 5.9 µm·m-1·K-1
Electrical Resistivity: (20 °C) 331 nΩ·m
Tensile Strength: N/A
Molar Heat Capacity: 25.73 J·mol-1·K-1
Young's Modulus: 78 GPa
Shear Modulus: 30 GPa
Bulk Modulus: 110 GPa
Poisson Ratio: 0.37
Mohs Hardness: 5.5
Vickers Hardness: 1760 MPa
Brinell Hardness: 1700 MPa
Speed of Sound: (20 °C) 3010 m·s-1
Pauling Electronegativity: 1.3
Sanderson Electronegativity: N/A
Allred Rochow Electronegativity: 1.23
Mulliken-Jaffe Electronegativity: N/A
Allen Electronegativity: N/A
Pauling Electropositivity: 2.7
Reflectivity (%): N/A
Refractive Index: N/A
Electrons: 72
Protons: 72
Neutrons: 106
Electron Configuration: [Xe] 4f14 5d2 6s2
Atomic Radius: 159 pm
Atomic Radius,
non-bonded (Å):
2.23
Covalent Radius: 175±10 pm
Covalent Radius (Å): 1.64
Van der Waals Radius: 200 pm
Oxidation States: 4, 3, 2 (amphoteric oxide)
Phase: Solid
Crystal Structure: Hexagonal
Magnetic Ordering: paramagnetic
Electron Affinity (kJ·mol-1) 1.64
1st Ionization Energy: 658.52 kJ·mol-1
2nd Ionization Energy: 1437.64 kJ·mol-1
3rd Ionization Energy: 2248.12 kJ·mol-1
CAS Number: 7440-58-6
EC Number: 231-166-4
MDL Number: MFCD00011032
Beilstein Number: N/A
SMILES Identifier: [Hf]
InChI Identifier: InChI=1S/Hf
InChI Key: VBJZVLUMGGDVMO-UHFFFAOYSA-N
PubChem CID: 23986
ChemSpider ID: 22422
Earth - Total: 230 ppb
Mercury - Total: 177 ppb
Venus - Total: 241 ppb
Earth - Seawater (Oceans), ppb by weight: 0.008
Earth - Seawater (Oceans), ppb by atoms: 0.00028
Earth -  Crust (Crustal Rocks), ppb by weight: 3300
Earth -  Crust (Crustal Rocks), ppb by atoms: 380
Sun - Total, ppb by weight: 1
Sun - Total, ppb by atoms: 0.01
Stream, ppb by weight: N/A
Stream, ppb by atoms: N/A
Meterorite (Carbonaceous), ppb by weight: 170
Meterorite (Carbonaceous), ppb by atoms: 20
Typical Human Body, ppb by weight: N/A
Typical Human Body, ppb by atom: N/A
Universe, ppb by weight: 0.7
Universe, ppb by atom: 0.005
Discovered By: Dirk Coster and George de Hevesy
Discovery Date: 1922
First Isolation: Dirk Coster and George de Hevesy (1922)

Health, Safety & Transportation Information for Hafnium

Hafnium is not toxic; however, safety data for hafnium and its compounds can vary widely depending on the form. For potential hazard information, toxicity, and road, sea and air transportation limitations, such as DOT Hazard Class, DOT Number, EU Number, NFPA Health rating and RTECS Class, please see the specific material or compound referenced in the Products tab. The below information applies to elemental (metallic) Magnesium.

Safety Data
Material Safety Data Sheet MSDS
Signal Word Danger
Hazard Statements H228
Hazard Codes F
Risk Codes 11
Safety Precautions N/A
RTECS Number MG4600000
Transport Information N/A
WGK Germany nwg
Globally Harmonized System of
Classification and Labelling (GHS)
Flame-Flammables

Hafnium Isotopes

Naturally occurring hafnium (Hf) has five stable isotopes: 176Hf, 177Hf, 178Hf, 179Hf, and 180Hf.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
153Hf 152.97069(54)# 400# ms [>200 ns] Unknown 1/2+# N/A 1183.2 -
154Hf 153.96486(54)# 2(1) s ß+ to 154Lu; a to 150Yb 0+ N/A 1200.6 -
155Hf 154.96339(43)# 890(120) ms ß+ to 155Lu; a to 151Yb 7/2-# N/A 1208.68 -
156Hf 155.95936(22) 23(1) ms a to 152Yb; ß+ to 156Lu 0+ N/A 1226.07 -
157Hf 156.95840(21)# 115(1) ms a to 153Yb; ß+ to 157Lu 7/2- N/A 1234.15 -
158Hf 157.954799(19) 2.84(7) s ß+ to 158Lu; a to 154Yb 0+ N/A 1242.23 -
159Hf 158.953995(18) 5.20(10) s ß+ to 159Lu; a to 155Yb 7/2-# N/A 1250.31 -
160Hf 159.950684(12) 13.6(2) s ß+ to 160Lu; a to 156Yb 0+ N/A 1258.39 -
161Hf 160.950275(24) 18.2(5) s ß+ to 161Lu; a to 157Yb 3/2-# N/A 1266.46 -
162Hf 161.94721(1) 39.4(9) s ß+ to 162Lu; a to 158Yb 0+ N/A 1283.86 -
163Hf 162.94709(3) 40.0(6) s ß+ to 163Lu; a to 159Yb 3/2-# N/A 1291.94 -
164Hf 163.944367(22) 111(8) s ß+ to 164Lu 0+ N/A 1300.02 -
165Hf 164.94457(3) 76(4) s ß+ to 165Lu (5/2-) N/A 1308.1 -
166Hf 165.94218(3) 6.77(30) min ß+ to 166Lu 0+ N/A 1316.17 -
167Hf 166.94260(3) 2.05(5) min ß+ to 167Lu (5/2)- N/A 1324.25 -
168Hf 167.94057(3) 25.95(20) min ß+ to 168Lu 0+ N/A 1332.33 -
169Hf 168.94126(3) 3.24(4) min ß+ to 169Lu (5/2)- N/A 1340.41 -
170Hf 169.93961(3) 16.01(13) h EC to 170Lu 0+ N/A 1357.81 -
171Hf 170.94049(3) 12.1(4) h ß+ to 170Lu 7/2(+) N/A 1356.57 -
172Hf 171.939448(26) 1.87(3) y EC to 172Lu 0+ N/A 1373.96 -
173Hf 172.94051(3) 23.6(1) h EC to 173Lu 1/2- N/A 1372.73 -
174Hf 173.940046(3) 2.0(4)E+15 y a to 170Yb 0+ N/A 1380.8 0.16
175Hf 174.941509(3) 70(2) d EC to 175Lu 5/2- 0.54 1388.88 -
176Hf 175.9414086(24) Observationally Stable - 0+ N/A 1396.96 5.26
177Hf 176.9432207(23) Observationally Stable - 7/2- 0.7936 1405.04 18.6
178Hf 177.9436988(23) Observationally Stable - 0+ N/A 1413.12 27.28
179Hf 178.9458161(23) Observationally Stable - 9/2+ -0.6409 1421.2 13.62
180Hf 179.9465500(23) Observationally Stable - 0+ N/A 1429.28 35.08
181Hf 180.9491012(23) 42.39(6) d ß- to 181Ta 1/2- N/A 1437.36 -
182Hf 181.950554(7) 8.90(9)E+6 y ß- to 182Ta 0+ N/A 1436.12 -
183Hf 182.95353(3) 1.067(17) h ß- to 183Ta (3/2-) N/A 1444.2 -
184Hf 183.95545(4) 4.12(5) h ß- to 184Ta 0+ N/A 1452.28 -
185Hf 184.95882(21)# 3.5(6) min ß- to 185Ta 3/2-# N/A 1460.35 -
186Hf 185.96089(32)# 2.6(12) min ß- to 186Ta 0+ N/A 1459.12 -
187Hf 186.96459(43)# 30# s [>300 ns] Unknown N/A N/A 1467.19 -
188Hf 187.96685(54)# 20# s [>300 ns] Unknown 0+ N/A 1475.27 -
Hafnium Elemental Symbol

Recent Research & Development for Hafnium

  • Hafnium(IV) chloride complexes with chelating β-ketiminate ligands: Synthesis, spectroscopic characterization and volatility study. 2015 Sep 5 Patil SA, Medina PA, Antic A, Ziller JW, Vohs JK, Fahlman BD. Spectrochim Acta A Mol Biomol Spectrosc. 2015 Sep 5
  • Hafnium silicate: a new microwave dielectric ceramic with low thermal expansivity. 2015 Mar 21 Varghese J, Joseph T, Surendran KP, Rajan TP, Sebastian MT. Dalton Trans. 2015 Mar 21
  • Direct synthesis of macrodiolides via hafnium(iv) catalysis. 2015 Jun 16 de Léséleuc M, Collins SK. Chem Commun (Camb). 2015 Jun 16
  • Instability of metal 1,3-benzodi(thiophosphinoyl)methandiide complexes: formation of hafnium, tin and zirconium complexes of 1,3-benzodi(thiophosphinoyl)thioketone dianionic ligand 1,3-C6H4(PhPS)2CS(2.). 2015 Jul 8 Yang YX, Li Y, Ganguly R, So CW. Dalton Trans. 2015 Jul 8
  • Crystal structure of di-n-but-yl-bis-(η (5)-penta-methyl-cyclo-penta-dien-yl)hafnium(IV). 2015 Jan 10 Arndt P, Schubert K, Burlakov VV, Spannenberg A, Rosenthal U. Acta Crystallogr E Crystallogr Commun. 2015 Jan 10
  • Crystal structure of bis-(η(5)-cyclo-penta-dien-yl)(2,3-di-ethyl-butane-1,4-di-yl)hafnium(IV). 2015 Jan 1 Burlakov VV, Baumann W, Arndt P, Spannenberg A, Rosenthal U. Acta Crystallogr E Crystallogr Commun. 2015 Jan 1
  • Preparation of octahydro- and tetrahydro-1,10phenanthroline zirconium and hafnium complexes for olefin polymerization. 2015 Feb 28 Hwang EY, Park GH, Lee CS, Kang YY, Lee J, Lee BY. Dalton Trans. 2015 Feb 28
  • Aqueous hafnium sulfate chemistry: structures of crystalline precipitates. 2014 Oct 20 Kalaji A, Soderholm L. Inorg Chem. 2014 Oct 20
  • Monoclinic hafnium oxynitride supported on reduced graphene oxide to catalyse the oxygen reduction reaction in acidic media. 2014 Oct 14 Chisaka M, Sasaki H, Muramoto H. Phys Chem Chem Phys. 2014 Oct 14
  • The energy landscape of glassy dynamics on the amorphous hafnium diboride surface. 2014 Nov 28 Nguyen D, Mallek J, Cloud AN, Abelson JR, Girolami GS, Lyding J, Gruebele M. J Chem Phys. 2014 Nov 28