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72Hf178.49
Transition metal

Hafnium

Hafnium is a hard, silvery transition metal discovered in 1923 after being specifically predicted to exist by atomic theory. Chemically similar to zirconium and hard to separate from it, hafnium is now essential to nuclear reactor control and to modern computer chips.

Group · Period
4 · 6
At room temp
solid
Melts at
2506 K
Density
13.3 g/cm³
Discovered
1923

Uses

Hafnium’s ability to absorb neutrons efficiently, combined with its resistance to corrosion and heat, makes it valuable for nuclear reactor control rods — it’s a standard material in naval nuclear reactors, including those that power submarines and aircraft carriers. In a very different field, hafnium oxide has become a key material in modern electronics: since the mid-2000s, chipmakers have used a thin layer of hafnium oxide inside computer processor transistors as a “high-k” insulator, letting transistors keep shrinking without leaking excessive current. Hafnium is also used, alongside its chemical relative zirconium, in some superalloys and in the electrodes of plasma-cutting torches, where its properties help sustain a stable, high-temperature arc.

History

Hafnium’s discovery is unusual among the elements in that it was essentially predicted before it was found. Niels Bohr’s atomic theory suggested a missing element should exist with chemical properties very close to zirconium, and in 1923 Dutch physicist Dirk Coster and Hungarian chemist George de Hevesy, working in Copenhagen, found it hiding in zirconium ore, exactly where the theory said to look. They named it hafnium after Hafnia, the Latin name for Copenhagen, honoring the city where the discovery was made.

Fun facts

  • Hafnium was discovered because physicist Niels Bohr's atomic theory predicted a missing element would be found alongside zirconium — and it was.
  • Hafnium is used in the control rods of nuclear submarine reactors because it absorbs neutrons well and holds up under harsh conditions.
  • Hafnium compounds are used as an insulating layer inside the tiny transistors that make up modern computer processors.

Frequently asked questions

Why is hafnium used in nuclear reactor control rods?

Hafnium absorbs neutrons very effectively, which lets control rods made from it regulate the rate of a nuclear chain reaction. It also resists corrosion well and holds up mechanically under the heat and radiation inside a reactor core, which is part of why it's a preferred material for control rods in naval nuclear reactors like those used in submarines.

What does hafnium have to do with computer chips?

Since the mid-2000s, chipmakers have used hafnium oxide as a thin insulating layer inside the transistors of computer processors, replacing older materials that stopped working well as transistors shrank to a few nanometers. This "high-k" hafnium layer helps prevent unwanted current leakage in incredibly small transistors, making modern chips more efficient.

Why is hafnium so hard to separate from zirconium?

Hafnium and zirconium have nearly identical chemical behavior because of how their electrons are arranged, so they occur together in the same minerals and don't separate easily through ordinary chemical reactions. It took specialized techniques to isolate hafnium after it was first detected, and the two elements are still typically separated using more elaborate industrial processes rather than simple chemistry.

Compounds

3 notable compounds containing Hf

  • HfCindustrial

    Hafnium carbide

    An extremely hard, grey ceramic with one of the highest melting points of any known binary compound, giving it exceptional resistance to extreme heat.

    Used for: Ultra-high-temperature coatings for rocket nozzles and hypersonic vehicle surfaces

  • HfO2oxide

    Hafnium dioxide

    A hard, chemically inert white oxide with an unusually high dielectric constant, which let it replace silicon dioxide as the insulating layer in modern transistor gates.

    Used for: High-k gate dielectric in advanced semiconductor transistors

  • HfCl4halide

    Hafnium tetrachloride

    A white, moisture-sensitive solid that fumes in air as it hydrolyzes, serving as the key precursor for depositing hafnium compounds by vapor-phase processes.

    Used for: Precursor gas for depositing hafnium dioxide gate dielectrics

Isotopes

39 known isotopes

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IsotopeNatural abundanceHalf-lifeDecay modeMass excessBinding energy / nucleonDecay width
Hf-174 0.16% 2.0E+15 Y Alpha decay (100%) -55,844.58 keV 8,068.53 keV 7.23 × 10-39 eV
Hf-176 stable 5.26% Stable — -54,576.43 keV 8,061.36 keV —
Hf-177 stable 18.6% Stable — -52,880.75 keV 8,051.84 keV —
Hf-178 stable 27.28% Stable — -52,435.37 keV 8,049.44 keV —
Hf-179 stable 13.62% Stable — -50,463.04 keV 8,038.55 keV —
Hf-180 stable 35.08% Stable — -49,779.48 keV 8,034.93 keV —
Show all 39 isotopes
Hf-151 — — Unknown — — —
Hf-153 — — Unknown -27,300 keV 7,882 keV —
Hf-154 — 2 s Electron capture / beta-plus decay (100%), Alpha decay (0%) -32,730 keV 7,918 keV 2.28 × 10-16 eV
Hf-155 — 843 ms Electron capture / beta-plus decay (100%) -34,310 keV 7,929 keV 5.41 × 10-16 eV
Hf-156 — 23 ms Alpha decay (100%) -37,819.51 keV 7,952.67 keV 1.98 × 10-14 eV
Hf-157 — 115 ms Alpha decay (94%), Electron capture / beta-plus decay (14%) -38,855 keV 7,960 keV 3.97 × 10-15 eV
Hf-158 — 2.85 s Electron capture / beta-plus decay (55.7%), Alpha decay (44.3%) -42,102.4 keV 7,981.28 keV 1.60 × 10-16 eV
Hf-159 — 5.6 s Electron capture / beta-plus decay (65%), Alpha decay (35%) -42,852.61 keV 7,986.56 keV 8.15 × 10-17 eV
Hf-160 — 13.6 s Electron capture / beta-plus decay (99.3%), Alpha decay (0.7%) -45,938.75 keV 8,006.38 keV 3.35 × 10-17 eV
Hf-161 — 18.4 s Electron capture / beta-plus decay (99.87%), Alpha decay (0.13%) -46,315.82 keV 8,009.12 keV 2.48 × 10-17 eV
Hf-162 — 39.4 s Electron capture / beta-plus decay (99.992%), Alpha decay (0.008%) -49,168.43 keV 8,027.12 keV 1.16 × 10-17 eV
Hf-163 — 40.0 s Electron capture / beta-plus decay (100%), Alpha decay (0.0001%) -49,269.32 keV 8,028.01 keV 1.14 × 10-17 eV
Hf-164 — 111 s Electron capture / beta-plus decay (100%) -51,818.36 keV 8,043.81 keV 4.11 × 10-18 eV
Hf-165 — 76 s Electron capture / beta-plus decay (100%) -51,635.51 keV 8,042.87 keV 6.00 × 10-18 eV
Hf-166 — 6.77 m Electron capture / beta-plus decay (100%) -53,858.99 keV 8,056.44 keV 1.12 × 10-18 eV
Hf-167 — 2.05 m Electron capture / beta-plus decay (100%) -53,467.76 keV 8,054.19 keV 3.71 × 10-18 eV
Hf-168 — 25.95 m Electron capture / beta-plus decay (100%) -55,360.56 keV 8,065.55 keV 2.93 × 10-19 eV
Hf-169 — 3.24 m Electron capture / beta-plus decay (100%) -54,716.9 keV 8,061.78 keV 2.35 × 10-18 eV
Hf-170 — 16.01 h Electron capture (100%) -56,253.86 keV 8,070.88 keV 7.92 × 10-21 eV
Hf-171 — 12.1 h Electron capture / beta-plus decay (100%) -55,431.35 keV 8,066.07 keV 1.05 × 10-20 eV
Hf-172 — 1.87 Y Electron capture (100%) -56,402.23 keV 8,071.74 keV 7.73 × 10-24 eV
Hf-173 — 23.6 h Electron capture / beta-plus decay (100%) -55,411.79 keV 8,066.02 keV 5.37 × 10-21 eV
Hf-175 — 70 d Electron capture (100%) -54,481.76 keV 8,060.76 keV 7.54 × 10-23 eV
Hf-181 — 42.39 d Beta-minus decay (100%) -47,402.96 keV 8,022 keV 1.25 × 10-22 eV
Hf-182 — 8.90E+6 Y Beta-minus decay (100%) -46,049.64 keV 8,014.84 keV 1.62 × 10-30 eV
Hf-183 — 1.018 h Isomeric transition (100%), Beta-minus decay (100%) -43,283.55 keV 8,000.03 keV 1.24 × 10-19 eV
Hf-184 — 4.12 h Beta-minus decay (100%) -41,499.45 keV 7,990.72 keV 3.08 × 10-20 eV
Hf-185 — 3.5 m Beta-minus decay (100%) -38,319.8 keV 7,973.97 keV 2.17 × 10-18 eV
Hf-186 — 2.6 m Beta-minus decay (100%) -36,424.21 keV 7,964.3 keV 2.92 × 10-18 eV
Hf-187 — — Beta-minus decay (100%) -33,000 keV 7,947 keV —
Hf-188 — — Beta-minus decay (100%) -30,830 keV 7,936 keV —
Hf-189 — — Beta-minus decay (100%) -27,150 keV 7,917 keV —
Hf-190 — — Beta-minus decay (100%) -24,800 keV 7,905 keV —