Solid-state phase relationships in the calcia-titania-zirconia system at 1200 degrees C

Phase relationships were investigated in the CaO-TiO2-ZrO2 system at 1200 d egrees C for compositions containing <50 mol% CaO using X-ray diffraction a nd electron probe microanalysis. The existence of two previously reported t ernary phases, zirconolite (CaZrTi2O7) and calzirtite (Ca2Zr5Ti2O16), was c onfirmed, Each of these phases exhibited a significant range of homogeneity between TiO2 and ZrO2, while maintaining a nearly constant concentration o f CaO. The ternary solubilities of the constituent binary phases were found to be small (typically <1 mol%), with the exceptions of the perovskites (C aTiO3 and CaZrO3). These latter phases displayed mutual solubilities of at least 22 mol% but exhibited significant variations in composition from grai n to grain. Thermodynamic equilibrium was clearly not established in severa l samples, although most of the phase relationship information obtained was self-consistent.