Hafnium 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.Hafnium(IV) oxide is quite inert. It reacts with strong acids such as concentrated sulfuric acid and with strong bases. It dissolves slowly in hydrofluoric acid to give fluorohafnate anions. At elevated temperatures, it reacts with chlorine in the presence of graphite or carbon tetrachloride to give hafnium tetrachloride.
H 5221 (OTTO)Hafnium (IV) oxide pellets, 1-3 mm, 99.99% Cas 12055-23-1 - used in optical coatings, and as a high-κ dielectric in DRAM capacitors and in advanced metal-oxide-semiconductor devices.