Hafnium

Hafnium is a shiny, silvery-grey metal almost always found mixed with zirconium: the two are so chemically similar they were not distinguished until 1923. Unlike zirconium, hafnium absorbs neutrons strongly, making it ideal for nuclear reactor control rods. It is also used in the gate insulator of modern computer chip transistors.

• Atomic Number7272 protons, 72 electrons
• Atomic Mass178.49 u72× heavier than hydrogen
• State at Room TempSolidSolid
• Density13.3 g/cm³
• Melting / Boiling2232.8°C / 4602.9°C
• Discovered1923

What is Hafnium?

Hafnium is a transition metal in Group 4 below zirconium. With 72 protons, it is separated from zirconium with great difficulty. Hafnium oxide (HfO₂) has replaced silicon dioxide as the gate dielectric in the most advanced transistors since Intel's 45nm process in 2007, enabling Moore's Law to continue when traditional silicon gate insulators became too thin.

Named after Hafnia, the Latin name for Copenhagen, Denmark, by discoverers Dirk Coster and Georg von Hevesy in 1923. X-ray spectroscopy of zirconium ores confirmed hafnium's existence, it had been hiding in zirconium minerals for over a century.

Fact Hafnium and zirconium are the most chemically similar pair of elements in the entire periodic table. Their atoms are almost identical in size (despite hafnium having 32 more protons) because of the lanthanide contraction: the gradual shrinkage of atomic radius across the lanthanide series, which exactly compensates for the mass increase.

Where you find Hafnium

On Earth

Found in zirconium ores (zircon, baddeleyite) worldwide. Separated from zirconium by liquid-liquid extraction. Australia, South Africa, Ukraine are producers.

How we use Hafnium

• Control rods in naval nuclear reactors, hafnium absorbs neutrons far better than zirconium, which is transparent to them.. Nuclear reactor control rods
• HfO₂ gate dielectrics in advanced CMOS transistors below 45nm node.. Computer chips
• Hafnium carbide (HfC) is one of the highest-melting compounds known, used in ultra-high temperature aerospace applications.. Aerospace materials

Did you know? Hafnium and zirconium are the most chemically similar pair of elements in the entire periodic table. Their atoms are almost identical in size (despite hafnium having 32 more protons) because of the lanthanide contraction: the gradual shrinkage of atomic radius across the lanthanide series, which exactly compensates for the mass increase.

How it was discovered

Named after Hafnia, the Latin name for Copenhagen, Denmark, by discoverers Dirk Coster and Georg von Hevesy in 1923. X-ray spectroscopy of zirconium ores confirmed hafnium's existence, it had been hiding in zirconium minerals for over a century.

Deeper dive: hafnium properties and applications

{details} {name_from}

Moving to 73 protons on the periodic table takes us to the next element.