Polymorphs with a face-centered cubic structure at room temperature were prepared by heat treatment in a humid or H-containing atmosphere. A cubic structure at room temperature was prepared by the heat treatment of K3PO4 which was mixed with Al2O3. The lattice parameter was 0.4435nm for K3PO4-40wt%Al2O3. It was found that the ionic conductivities (table 166) were much higher for the cubic phases than for other polymorphs, and that proton conduction occurred in these materials.

B.Zhu, B.E.Mellander, J.Chen: Materials Research Bulletin, 1993, 28[2], 321-8

Table 166

Ionic Conductivities of K3PO4-Al2O3