Characteristic

Hafnium(IV) oxide is the inorganic compound with the formula HfO₂. Also known as hafnia, this colourless solid is one of the most common and stable compounds of hafnium. It is an electrical insulator with a band gap of 5.3~5.7 eV. Hafnium dioxide is an intermediate in some processes that give hafnium metal.

Chemical formula：HfO₂

Molar mass：210.49 g/mol

Appearance：off-white powder

Density：9.68 g/cm³, solid

Melting point：2,758 °C (4,996 °F; 3,031 K)

Boiling point：5,400 °C (9,750 °F; 5,670 K)

Solubility in water：insoluble

Magnetic susceptibility (χ)：−23.0·10⁻⁶ cm³/mol

Application

Hafnia is used in optical coatings, and as a high-κ dielectric in DRAM capacitors and in advanced metal-oxide-semiconductor devices.

In recent years, hafnium oxide (as well as doped and oxygen-deficient hafnium oxide) attracts additional interest as a possible candidate for resistive-switching memories and CMOS-compatible ferroelectric field effect transistors (FeFET memory) and memory chips.

Because of its very high melting point, hafnia is also used as a refractory material in the insulation of such devices as thermocouples, where it can operate at temperatures up to 2500 °C.

Multilayered films of hafnium dioxide, silica, and other materials have been developed for use in passive cooling of buildings. The films reflect sunlight and radiate heat at wavelengths that pass through Earth's atmosphere, and can have temperatures several degrees cooler than surrounding materials under the same conditions.

HfO2_MSDS.pdf