Microwave dielectric properties of H₃BO₃–CuO co-doped 0. 85BaTi₄O₉–0.15BaZn₂Ti₄O₁₁ ceramics

The effects of x wt% H₃BO₃ + 1.0 wt% CuO (x = 1.0–10.0) co-doping on microstructure and microwave dielectric properties of 0.85BaTi₄O₉–0.15BaZn₂Ti₄O₁₁ (BZT) have been investigated according to the conventional solid-state reaction in this study. The X-Ray Diffraction results showed that the main crystal phase in the sintered ceramics was BaTi₄O₉. The addition of H₃BO₃–CuO resulted in the liquid phase sintering mechanism, which effectively improved their relative densities and lowered the sintering temperature. As H₃BO₃ doping amount increased from 1.0 to 10.0 wt%, the relative density and ε_r displayed a sharp increase at first and then a decline when x = 6.0 wt%. The Q × f value experienced a continuously decrease with the addition of H₃BO₃ when sintered at sintering temperature. The development in τ_f was different, increasing persistently with the increase of doping amount at different sintering temperature. The H₃BO₃–CuO co-doped 0.85BaTi₄O9–0.15BaZn₂Ti₄O₁₁ ceramics had a low sintering temperature of 1000 °C and a high ε_r value. Good microwave dielectric properties with values of ε_r = 35.0, Q × f = 20,700 GHz and τ_f = 12.0 ppm/°C were obtained in the BZT ceramics with 6.0 wt% H₃BO₃ and 1.0 wt% CuO sintered at 1000 °C for 2 h.