Microwave dielectric properties and low-temperature sintering mechanism in (Ca,Bi)(Mo,V)O4 ceramics

Abstract In this work, high-quality (Ca1-xBix)(Mo1-xVx)O4 (0.15 ≤ x ≤ 0.5) ceramics with a tetragonal scheelite structure were prepared at sintering temperatures of 800–925 ℃. Their microstructures, alternating current impedance, and microwave dielectric properties were studied comprehensively. Through scanning electron microscopy and transmission electron microscopy analyses, the low-temperature sintering mechanism was clarified to be the dissolution–precipitation process of small particles in the liquid phase of the grain boundary. The increase in point defects led to an increase in extrinsic loss, which might be the main extrinsic factor affecting the Q×f (Q = quality factor = 1/dielectric loss, f = resonant frequency) value. The (Ca0.65Bi0.35)(Mo0.65V0.35)O4 ceramic sintered at 875 ℃ for 4 h exhibited superior microwave dielectric properties, with permittivity (er) ~ 17, Q×f value ~ 12080 GHz (at 9.86 GHz), and near-zero temperature coefficient of resonance frequency (τf) ~ + 3.6 ppm/℃; thus, the ceramic has great potential for the LTCC application.