Microwave dielectric properties and compatibility with silver of low-fired Ba₅Nb₄O₁₅ ceramics by BaCu(B₂O₅) addition

The influence of BaCu(B₂O₅) (BCB) addition on the sintering temperature and microwave dielectric properties of Ba₅Nb₄O₁₅ ceramics has been investigated. The addition of small amount of BCB can effectively lower the sintering temperature of Ba₅Nb₄O₁₅ ceramics from 1400 to 875 °C and induce no obvious degradation of the microwave dielectric properties. The reduced sintering temperature was attributed to the BCB liquid phase. Typically, the 1.5 wt% BCB-added Ba₅Nb₄O₁₅ ceramic sintered at 875 °C for 2 h exhibited good microwave dielectric properties of Q × f = 28,655 GHz, ε_r = 40.2, and τ_f = 60 ppm/°C. The dielectric ceramic demonstrated stability against the reaction with the Ag electrode, which suggests that the ceramics could be applied in multilayer microwave devices requiring low sintering temperatures.