Influences of B2O3/CuO additions on the sintering behavior, microstructure and microwave dielectric properties of 6Nd[(Zn0.7Co0.3)0.5Ti0.5]O3–4(Na0.5Nd0.5)TiO3 ceramics

Abstract

B2O3 and CuO were codoped into 6Nd[(Zn0.7Co0.3)0.5Ti0.5]O3–4(Na0.5Nd0.5)TiO3 (abbreviated as 6NZCT–4NNT) ceramics as sintering aids. The influences of the sintering aids on the sintering characteristics, microstructure and microwave dielectric properties of the 6NZCT–4NNT ceramics were systematically investigated as a function of the proportion of B2O3 and CuO. Codoping could greatly reduce the sintering temperature from 1410 °C to 1150 °C, indicating that B2O3/CuO are good sintering aids for 6NZCT–4NNT ceramics. The B2O3/CuO sintering aids had no significant impact on the phase purity of the investigated ceramics, even though a solid solution was formed due to Cu2+ ion substitution. However, they had evident influences on the surface morphology and grain size. The average grain size was enlarged with increasing amounts of CuO in the B2O3/CuO sintering aids. Remarkable deterioration of the microwave dielectric properties for 6NZCT-4NNT ceramics was not observed when codoping an appropriate amount of B2O3 and CuO. The 6NZCT–4NNT ceramics codoped with 2.0 mol% B2O3 and 2.0 mol% CuO sintered at 1150 °C for 3 h exhibited a homogeneous microstructure and promising microwave dielectric properties: an appropriate dielectric constant (εr = 49.37), a high quality factor (QF = 47,295 GHz), and a near-zero temperature coefficient of resonant frequency (TCF = +0.9 ppm/°C).