Effects of firing temperature on morphology and crystal structure of zirconiumbis(monohydrogen phosphate) and its alkali salts

In zirconiumbis(monohydrogen phosphate)monohydrate, the stability of water of crystallization and of the crystal form was strongly influenced by its crystal size. The water of crystallization of a smaller crystal was completely released on heating to 200° C while a part of this water was held at 300° C in a larger crystal with a diameter of several micrometres. While a smaller crystal was decomposed by heating to 900° C and cubic zirconium pyrophosphate was formed, for a larger crystal,-layered zirconium pyrophosphate was formed instead of cubic zirconium pyrophosphate and a layered structure was held. For the Na₂-, K₂- and Rb₂-forms, good layer structure was retained even by heating to 1000° C. For the Li₂-form, the layer structure was decomposed on heating at or above 900° C. The thermal stability of the layered structure increased with increasing crystal size and ionic radii of the alkali cation.