Synthesis of BaCu(B₂O₅) ceramics and their effect on the sintering temperature and microwave dielectric properties of Ba(Zn _1/3Nb_2/3)O₃ ceramics

BaCu(B₂O₅) ceramics were synthesized and their microwave dielectric properties were investigated. BaCu(B₂O ₅) phase was formed at 700°C and melted above 850°C. The BaCu(B₂O₅) ceramic sintered at 810°C had a dielectric constant (ε_r) of 7.4, a quality factor (Q × f) of 50000 GHz and a temperature coefficient of resonance frequency (τ_f) of -32 ppm/°C. As the BaCu(B₂O₅) ceramic had a low melting temperature and good microwave dielectric properties, it can be used as a low-temperature sintering aid for microwave dielectric materials for low temperature co-fired ceramic application. When BaCu(B₂O₅) was added to the Ba(Zn_1/3Nb_2/3)O₃ (BZN) ceramic, BZN ceramics were well sintered even at 850°C. BaCu(B ₂O₅) existed as a liquid phase during the sintering and assisted the densiflcation of the BZN ceramic. Good microwave dielectric properties of Q × f = 16000 GHz, ε_r = 35, and τ _f = 22.1 ppm/°C were obtained for the BZN+6.0 mol% BaCu(B ₂O₅) ceramic sintered at 875°C for 2 h.