Ceramics-Silikáty 53, (1) 5 - 8 (2009)

Low-melting H₃BO₃, acting as sintering aid, was used to reduce the sintering temperature of 5 wt.% CaTiO₃-doped (Zn_0.65Mg_0.35)TiO₃ ceramics. The sintering behaviors, microstructures and microwave dielectric properties with different amounts of H₃BO₃ addition were investigated. The results showed that H₃BO₃ additive was very effective for lowering the sintering temperature and improving the bulk density during sintering. This was due to the promotion of liquid-phase sintering. In the case of 0.25 wt.% H₃BO₃ addition, fine-grained structure was observed, whereas abnormal grain growth was occurred when 3 wt.% H₃BO₃ was doped. It was found that the addition of H₃BO₃ improved the dielectric constant (ε_r) and quality factor (Q × f) .When 5 wt.% CaTiO₃ and 3 wt.% H₃BO₃ were added, the (Zn_0.65Mg_0.35)TiO₃ ceramics could be sintered at 950~1000°C and showed excellent microwave dielectric properties: ε ≈ 20, Q × f > 48000 GHz (at 8 GHz) and τ_f ≈ 5 ppm/°C.