A MODIFIED CA-BETA''-AL2O3 STRUCTURE

Polycrystalline Cabeta''/beta type-Al2O3 made by direct sintering has been studied by selected area electron diffraction (SAED), EDX and hig h-resolution electron microscopy (HREM). There is a new phase besides Cabeta''-Al2O3 in the electrolyte. This new phase is different from Ca beta''-Al2O3 and is called modified Cabeta''-Al2O3 (M-beta'' phase). I t has a rhombohedral structure with lattice parameters a = 5.63 angstr om, c = 81.51 angstrom. Its composition is nearly Al: Ca = 14:1. The i onic conductivity which is very high is also discussed.