hafnium

Hafnium is a chemical element with the symbol Hf and atomic number 72. It is a transition metal in group 4 and was discovered in 1923 by Dirk Coster and George de Hevesy while studying zirconium. The name hafnium is derived from Hafnia, the Latin name for Copenhagen.

Hafnium is a silvery-gray, ductile metal with a very high melting point and strong resistance to corrosion, largely thanks to a stable oxide layer. It occurs together with zirconium in zirconium-bearing minerals and is typically obtained as a byproduct of zirconium processing. Its chemistry is very similar to that of zirconium, and separating the two elements historically relied on differences in their compounds and neutron capture behavior.

In nature, hafnium consists of several stable isotopes, with Hf-180 being the most abundant. Hafnium forms various compounds, including hafnium dioxide (HfO2), hafnium tetrachloride (HfCl4), and hafnium carbide (HfC). It has a relatively high neutron absorption cross-section, making it valuable for neutron-related applications, particularly when high purity is required.

Industrial uses of hafnium include its role in nuclear technology, where hafnium-containing materials serve in control rods and neutron shielding in some reactor designs. In electronics, hafnium oxide is widely used as a high-k dielectric in advanced CMOS transistors, providing a replacement for silicon dioxide in gate stacks. Hafnium alloys and compounds are employed in high-temperature coatings and special ceramics for aerospace and chemical processing.

Global production occurs mainly as a byproduct of zirconium mining and processing. Major producers include China, Russia, and the United States. Hafnium is marketed in metal, alloy, and compound forms for research, industrial, and commercial applications.

---