The stability and dielectric performance of BiNbO_4 prepared by citrate method assisting sintering process

摘要

Low-temperature β phase BiNbO_4 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-p can be obtained between 700 and 750℃ 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 ℃. Above 750 ℃, both the calcination temperature and incubation time can induce the abnormal phase transition from Low-β to a 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 BiNbO_4 ceramics were investigated to analyze the influence of phase of BiNbO_4 powders precursors, especially the effect of phase transition of Low-p. It's found that BiNbO_4 powders firstly calcined at 700 ℃ is the best precursor to prepare dense ceramics with uniform grain size and the dielectric permittivity and dielectric loss of BiNbO_4 ceramics prepared at 1000 ℃ is 56.6 and 0.001 at 10kHz, respectively.