Effects of Bi2O3 phase transition on sintering behavior, microwave dielectric properties of novel CeO2–Bi2O3 ceramics

Series of novel Bi2O3–CeO2 (Bi:Ce = 1:4∼6:1) ceramics were successfully fabricated, and the effects from both phase transition and content variation of Bi2O3 on the sintering temperature, microstructure and microwave dielectric properties had been investigated. The phase composition of Bi2O3–CeO2 series ceramics were indexed as CeO2 (Fm-3m) and Bi2O3 (P-421c or P21/c). Ceramics with Bi2O3 of P21/c phase had the optimum sintering temperature below 900 °C, which was suitable for LTCC. When Bi:Ce ratio changed from 1:2 to 1:3, the Bi2O3 phase changed from P21/c to P-421c, leading to an abrupt increase in the optimal sintering temperature (from 860 °C to 1000 °C), and also resulted in microstructure of Bi2O3–CeO2 ceramics evolving from vague to clear. For microwave dielectric properties, the dielectric constant and temperature coefficient were dependent on the content of Bi2O3, while the Q × ƒ values were related to the microstructure, which was affected by phase transition and content of Bi2O3. And the typical microwave dielectric properties were εr = 29.0–32.5, Q × ƒ = 17648 GHz–24278 GHz, τƒ = −20.77 ppm/°C ∼ −38.76 ppm/°C.