Effects of CaTiO3 addition on the densification and microwave dielectric properties of BiSbO4 ceramics

In this study, the effects of CaTiO3 addition on the sintering characteristics and microwave dielectric properties of BiSbO4 were investigated. Pure BiSbO4 achieved a sintered density of 8.46 g/cm3 at 1100 °C. The value of sintered density decreased with increasing CaTiO3, and sintering at a temperature higher than 1100 °C led to a large weight loss (>2 wt%) caused by the volatile nature of the compound. Samples either sintered above 1100 °C or with a CaTiO3 content exceeding 3 wt% showed poor densification. SEM micrographs revealed microstructures with bimodal grain size distribution. The size of the smaller grains ranged from 0.5 to 1.2 μm and that of the larger grains between 3 and 7 μm. The microwave dielectric properties of the (1−x) BiSbO4−x CaTiO3 ceramics are dependent both on the x value and on the sintering temperature. The 99.0 wt% BiSbO4-1.0 wt% CaTiO3 ceramic sintered at 1100 °C reported overall microwave dielectric properties that can be summarized as εr≈21.8, Q×f≈61,150 GHz, and τf≈−40.1 ppm/°C, all superior to those of the BiSbO4 ceramics sintered with other additives.