Zirconia formation by reaction of zirconium sulfate in molten alkali-metal nitrates or nitrites

Thermogravimetry up to 500 °C reveals several multi-stage reactions between Zr(SO4)2 and molten alkali-metal nitrates which form poorly crystallised mixtures of tetragonal and monoclinic zirconia. The use of NaNO3 gives incomplete transformations. The addition of NaCl as well as the use of LiNO3-KN03, leads the reaction to completion; the increase of basicity by the addition of Na2CO3 also has the same effect, if it is assumed that Na2ZrO3 is formed together with ZrO2. Pure and finely divided tetragonal zirconia is produced by a single-stage reaction at a temperature lower than 300 °C, when the basicity of the medium is increased by replacing LiN03–KNO3 by NaNO2–KNO3