Temperature Inversions of Anhydrous Gallium Orthophosphate

Crystalline GaPO 4 was prepared in a hydrothermal bomb at 200° to 300°C. It was found to be isostructural with the berlinite form of AlP04. Thermal analysis and high‐temperature X‐ray techniques were utilized to show that the analogy extends to some of the polymorphic forms of AlPO 4 as well. Three forms of GaPO 4 , corresponding to the berlinite, high‐cristobalite, and low‐cristobalite forms of the A1PO 4 system, were observed. No evidence was found to indicate the existence of a tridymite form.