Effects of Glass Addition on Microwave Dielectric Properties of Zn_0.95Mg_0.05TiO₃ + 0.25TiO₂ Ceramics

The effects of Bi₂O₃ addition on the microwave dielectric properties and the microstructures of Zn_0.95Mg_0.05TiO₃ + 0.25TiO₂ with 1 wt% 3ZnO–B₂O₃ (ZnBO–ZMT') ceramics prepared by conventional solid-state routes have been investigated. In a preliminary study, it was shown that ZnBO–ZMT' ceramics can be sintered to a theoretical density higher than 95% at 900°C. In this study, the effects of Bi₂O₃ additions of up to 10 wt% on the sintering characteristics of the ZnBO–ZMT' ceramics was investigated at the sintering temperatures ranging from 860 to 960°C. Sintered ceramic samples were characterized by X-ray diffraction and scanning electron microscopy (SEM). It was found that as the content of Bi₂O₃ increases, the density of the sintered ceramics increases, and the sintering temperature can be lowered to 880°C by adding 5 wt% Bi₂O₃. The ZnBO–ZMT' ceramic with 5 wt% Bi₂O₃ addition sintered at 880°C exhibits the optimum dielectric properties: Q×f=4000 GHz, ε_r=24.6, and τ_f=-14 ppm/°C. Unlike the ZnBO–ZMT' ceramic without Bi₂O₃ addition sintered at above 920°C, the ceramics with Bi₂O₃ additions show no Zn₂TiO₄ existence at 960°C sintering. It is therefore demonstrated that the addition of Bi₂O₃ can suppress the formation of Zn₂TiO₄ in ZnBO–ZMT' ceramics.