The stability and dielectric performance of BiNbO4 prepared by citrate method assisting sintering process

Abstract

Low‐temperature β phase BiNbO4 powders (denoted as Low‐β) were prepared by a citrate method using home‐made water‐soluble niobium precursors. The stability of Low‐β was systematically investigated from the aspects including calcination temperature, incubation time, and stress existing in pellets. Pure Low‐β can be obtained between 700 and 750 °C and the crystal evolution of Low‐β has not completed yet, compared with high‐temperature β phase. Low‐β is kinetically stable and no phase transition occurs when increasing the incubation time below 750 °C. Above 750 °C, both the calcination temperature and incubation time can induce the abnormal phase transition from Low‐β to α phase; also, stress existing in pellets can effectively activate the phase transition of Low‐β. We can conclude that the Low‐β is thermodynamically unstable, while in kinetics, Low‐β is stable. The dielectric properties of BiNbO4 ceramics were investigated to analyze the influence of phase of BiNbO4 powders precursors, especially the effect of phase transition of Low‐β. It's found that BiNbO4 powders firstly calcined at 700 °C is the best precursor to prepare dense ceramics with uniform grain size and the dielectric permittivity and dielectric loss of BiNbO4 ceramics prepared at 1000 °C is 56.6 and 0.001 at 10 kHz, respectively.