AlPO4 solid solutions containing Ca and Zn phosphates

Portions of an Al₂O₃·3H₂OH₃PO₄CaO compositional triangle were examined at 300°C for a solid solution of Ca (presumably in the form of Ca(H₂PO₄)₂) in the Cristobalite AlPO₄ crystal structure. X-ray diffraction patterns of the various compositions showed the existence of such a solid solution including a lattice parameter change. The limit of the solid solution was approximated at composition 2CaO, Al₂O₃·3H₂O, 6H₃PO₄. This solid solution, however, proved to be unstable at 800°C, but was stabilized by the addition of $\text{1}\text{4}$ mole ZnO at the limit composition.Three points in an Al₂O₃·3H₂OH₃PO₄ZnO compositional triangle were also examined and evidence of solid solution found including a lattice parameter change.