Microwave dielectric properties of V ₂ O _5/ CeO ₂ doped (Mg _0.95 Ca _0.05 )TiO ₃ ‐MgO and their application to a dielectric filter

Abstract The phase composition, microstructure, sintering characteristics, and microwave dielectric properties of nonstoichiometric MgTiO ₃ ‐CaTiO ₃ ceramics containing an additional 0.2 mol MgO, compositely doped with various amounts of V ₂ O ₅ and CeO ₂ additives, were studied. The results revealed that adding an optimum amount of V ₂ O ₅ and CeO ₂ could effectively impede second‐phase formation in Mg _0.95 Ca _0.05 TiO ₃ ‐MgO. High amounts of Mg ²⁺ can react with MgTi ₂ O ₅ 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 V ₂ O ₅ and CeO ₂ . Mg _0.95 Ca _0.05 TiO ₃ ‐MgO doped with 0.75 wt% CeO ₂ exhibited excellent frequency and temperature stabilities. In particular, when co‐doped with 0.5 wt% V ₂ O ₅ and 0.75 wt% CeO ₂ , Mg _0.95 Ca _0.05 TiO ₃ ‐MgO exhibited optimum properties after sintering at 1300°C for 2 h; a dielectric constant ε _r ∼ 19.92 (7 GHz),a Q×f value ∼ 65,236 GHz, and a τ _f 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 Mg _0.95 Ca _0.05 TiO ₃ ‐MgO sample co‐doped with 0.5 wt% V ₂ O ₅ and 0.75 wt% CeO ₂ .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.