Effect of Li3PO4 addition on the sintering temperature, phase, microstructure, and electrical properties of BaTiO3

Decreasing the sintering temperature of BaTiO3 without deteriorating the dielectric properties is technologically important in the fabrication of multi-layer ceramic capacitors (MLCCs). Consequently, ceramic formulations based on the (1 − x)BaTiO3–xLi3PO4 (x = 0, 0.01, 0.03, 0.05, and 0.1) were prepared. The use of Li3PO4 as a sintering aid lowered the optimum sintering temperature from 1350 to 1150 °C but X-ray diffraction revealed the formation of BaLiPO4 for x = 0.01–0.05 and an additional secondary LiPO3 phase at x = 0.1. The room temperature dielectric constant decreased from ~4288 to ~3600 and the remnant polarization and coercive field also decreased from 6.70 to 3 µC/cm2 and 3.32 to 2.5 kV/cm, respectively, as x increased from 0 to 0.05 but more importantly the phase transition temperature remained essentially constant, an important factor in the fabrication of temperature stable devices. Moreover, the bulk and grain boundary conductivity decreased as x increased to 0.05, possibly related to a decrease in the grain size from 50 to 1 μm. These results suggest that Li3PO4 may have technological benefits in the fabrication of MLCCs.