文摘
Dense Bi4Ge3O12 ceramics sintered at 850 °C had a relative permittivity (εr) of 15.7, temperature coefficient of resonant frequency (τf) of −24.2 ppm/°C, and quality factor (Q×f) of 28,361 GHz. However, because of the existence of Bi12GeO20 as a secondary phase, the microwave dielectric properties of Bi4Ge3O12 would be degraded. Therefore, to avoid the formation of the Bi12GeO20 secondary phase, Bi2O3-deficient Bi4-xGe3O12-1.5x ceramics with 0.1≤x≤0.6 were sintered at 850 °C. A single phase of Bi3.6Ge3O11.4 (x=0.4) ceramic sintered at 850 °C for 5 h without any secondary phase exhibited suitable microwave dielectric properties for a ceramic substrate: εr=14.9, τf =−9.5 ppm/°C, and Q×f=53,277 GHz.