Microwave dielectric properties of V₂O_5/CeO₂ doped (Mg_0.95Ca_0.05)TiO₃‐MgO and their application to a dielectric filter

Abstract

The phase composition, microstructure, sintering characteristics, and microwave dielectric properties of nonstoichiometric MgTiO3‐CaTiO3 ceramics containing an additional 0.2 mol MgO, compositely doped with various amounts of V2O5 and CeO2 additives, were studied. The results revealed that adding an optimum amount of V2O5 and CeO2 could effectively impede second‐phase formation in Mg0.95Ca0.05TiO3‐MgO. High amounts of Mg2+ can react with MgTi2O5 to reduce the content of the secondary phase. The addition facilitated the densification of the microstructure and reduction of sintering temperature. Moreover, the dielectric performances of the material were significantly influenced by V2O5 and CeO2. Mg0.95Ca0.05TiO3‐MgO doped with 0.75 wt% CeO2 exhibited excellent frequency and temperature stabilities. In particular, when co‐doped with 0.5 wt% V2O5 and 0.75 wt% CeO2, Mg0.95Ca0.05TiO3‐MgO exhibited optimum properties after sintering at 1300°C for 2 h; a dielectric constant εr ∼ 19.92 (7 GHz),a Q×f value ∼ 65,236 GHz, and a τf value ∼ −2.03 ppm/°C. This indicates the potential of the material for microwave communication applications. Finally, a dielectric filter with a center frequency of 11.55 GHz was successfully designed and fabricated using a Mg0.95Ca0.05TiO3‐MgO sample co‐doped with 0.5 wt% V2O5 and 0.75 wt% CeO2.The filter exhibited excellent performance with a bandwidth of less than 1.5 is about 40 MHz, the loss at the center frequency point was 0.7 dB, and the 3‐dB bandwidth exceeded 200 MHz, which holds a significant practical value.