Effects of Gd doping on the sintering and microwave dielectric properties of BiNbO4 ceramics

Gd3+ was chosen as a substitute for Bi3+ in BiNbO4 ceramics, and the substitution effects on the sintering performance and microwave dielectric properties were studied in this paper. The high temperature triclinic phase was observed only in the Bi0.98Gd0.02NbO4 ceramics when sintered at 920 C. Both bulk den’sities and dielectric constant (er) increased with the sintering temperature, while decreased with the Gd content. The quality factor (Q) exhibited a correlation to the Gd content and the microstructures of Bi1–xGdxNbO4 ceramics. At the sintering temperature of 900 C, Bi0.992Gd0.008NbO4 ceramics exhibited microwave dielectric properties of er ~ 43.87, Q · f ~ 16,852 GHz (at 4.3 GHz), and its temperature coefficient of resonant frequency (sf) was found to be near-to-zero.