Effect of CaO additive on the phase constitution and microstructure of fused BaZrO₃ refractory

The CaO doped fused BaZrO₃ is a promising refractory for induction melting of titanium alloys. Therefore, the present study investigated the effect of CaO additive on the phase constitution and microstructure of the fused BaZrO₃ refractory by x-ray diffraction (XRD) and scanning electron microscopy (SEM). Results revealed that the fused BaZrO₃ refractory contained a significant amount of ZrO₂ as a second phase. After doping CaO, the ZrO₂ phase was absent along with the formation of phase-1 (Ba_1−xCa_xZrO_3−σ) and phase-2 (Ba_1−yCa_yZrO_3−σ) due to the different replacement ratio of Ca for Ba-site. The fraction of phase-1 was increasing as well as the decreasing fraction of phase-2 with the increased content of CaO additive. Meanwhile, CaO functions as a role of sintering additive for improving the densification of fused BaZrO₃ refractory due to the generation of solid solutions. The result of interaction analysis indicated that CaO should be a suitable additive for improving the thermodynamic stability of fused BaZrO₃ refractory. It provides an effective framework for the further development of CaO doped fused BaZrO₃ refractory for induction melting of alloys rich in titanium. (paper)