Low-Temperature Sintering of Ba₅(Nb_1-xV_x)₄O₁₅ Ceramics with H₃BO₃

Ba5(Nb1-xVx)4O15 (0≤x≤0.1) ceramics doped with H3BO3 were prepared by solid-state reaction. The effects of H3BO3 additives on the sinterability and microwave dielectric properties of the ceramics were investigated. The formation of a single phase was identified with the X-ray powder diffraction patterns of Ba5(Nb1-xVx)4O15 ceramics in the composition x from 0 to 0.025. Minor phases including Ba3(VO4)2 were formed as the secondary phase for the compositions with x>0.025. The dielectric constants (εr) of the ceramics increased firstly from 38.7 to 39.69 with x increasing from 0 to 0.01, and, then decreased to 36.91 with x=0.1, meanwhile, the unloaded quality factor and temperature coefficient of resonance frequency (τf) decreased as the x value increased from 0 to 0.1. Microwave dielectric properties, εr=36.91, Q×f =16,167GHz and τf =35ppm/°C, were obtained for Ba5(Nb0.9V0.1)4O15 ceramics with 1wt% H3BO3 sintered at 900°C for 2h.