Microwave dielectric properties and low temperature sintering of Ba3Ti4−x(Mg1/3Nb2/3)xNb4O21 ceramics with BaCu(B2O5) addition

Microwave dielectric ceramics of Ba3Ti4−x(Mg1/3Nb2/3)xNb4O21 solid solutions (BTMNN-x, x = 0–4) were prepared via the conventional solid-state reaction method. The X-ray powder diffraction analysis revealed that the BTMNN-x ceramics formed complete solid solutions with hexagonal structure. The dielectric constant (er) and the temperature coefficient of the resonant frequency (τf) of BTMNN-x ceramics decreased with the increase of x, while the quality factor (Q × f) enhanced with increasing the substitution content. In addition, a small amount of BaCu(B2O5) (BCB) additive can effectively lower the sintering temperature of BTMNN ceramics. The 1.5 wt% BCB doped BTMNN-2 ceramics can be sintered at 950 °C and have good microwave dielectric properties of er = 50, Q × f = 10,500 GHz and τf = 18 ppm/°C, which makes it possible to be a promising candidate for mid-permittivity low temperature co-fired ceramic materials.