(1-x)MgTi₂O₅–xCaTiO₃ microwave dielectric composites with near–zero temperature coefficient of resonant frequency

MgTiO₃ and Mg₂TiO₄ are important commercial microwave dielectric ceramics, while MgTi₂O₅ ceramic as the last stable phase in MgO–TiO₂ binary phase diagram has not attracted similar attention. In this study, MgTi₂O₅ ceramics were prepared by solid-state sintering, and the optimal microwave dielectric properties with ε_r = 18.6, Qf = 53,000 GHz, and τ_f = − 48.8 ppm/℃ were obtained for the sintering temperature of 1250 °C. CaTiO₃ with a large positive τ_f was further introduced to compensate the large negative τ_f of MgTi₂O₅, and the optimal microwave dielectric properties of ε_r = 22.7, Qf = 39,900 GHz, and τ_f = 4.9 ppm/℃ were obtained in 0.9MgTi₂O₅–0.1CaTiO₃ composite sintered at 1250 °C. Although the Qf value of the present 0.9MgTi₂O₅–0.1CaTiO₃ composite is lower than that of the commercial MgTiO₃–CaTiO₃ counterpart with near-zero τ_f, it is expected to be improved by eliminating the color centers caused by oxygen deficiencies in MgTi₂O₅. Besides, the 0.9MgTi₂O₅–0.1CaTiO₃ composite has a higher ε_r and a lower sintering temperature, indicating its potential application prospects in future microwave communications.