Microwave dielectric properties and low temperature sintering of Ba_3Ti_(4-x)(Mg_(1/3)Nb_(2/3))_xNb_4O_(21) ceramics with BaCu(B_2O_5) addition

摘要

Microwave dielectric ceramics of Ba_3Ti_(4_x) (Mg_(1/3)Nb_(2/3))_xNb_4O_(21) 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 (ε_r) and the temperature coefficient of the resonant frequency (τ_f) 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(B_2O_5) (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 ℃ and have good microwave dielectric properties of ε_r = 50, Q × f = 10,500 GHz and τ_f = 18 ppm/℃, which makes it possible to be a promising candidate for mid-permittivity low temperature co-fired ceramic materials.