Hafnium dioxide, white powder, has three crystal structures: monoclinic, tetragonal and cubic. The densities are 10.3, 10.1 and 10.43g/cm3 respectively. The melting point is 2780 ~ 2920K. The boiling point is 5400K. The coefficient of thermal expansion is 5.8×10-6/℃.
It is insoluble in water, nitric acid, but soluble in concentrated and hydrofluoric acid. It is produced by thermal decomposition or hydrolysis of compounds such as hafnium sulfate and hafnium oxychloride. For the production of metal hafnium and hafnium alloy raw materials. Used as refractory material, anti-radioactive coating and catalyst.