Study on the Phase Transformation of MgMoO4 Induced by Cu2+ Doping and Its Microwave Dielectric Properties

Herein, Mg 1- x Cu x MoO 4 (0≤ x ≤0.1) ceramics were synthesized via solid-state reaction for low-temperature co-fired ceramic (LTCC) applications. The effects of Cu 2+ substitution on phase evolution, microstructure, and microwave dielectric properties were systematically investigated. Cu 2+ incorporation, driven by Jahn-Teller distortion, induced a phase transition from monoclinic β -MgMoO 4 to triclinic α -MgMoO 4 , accompanied by a sequential process of solid-solution formation, phase transformation, and secondary-phase precipitation. Enhanced performance is attributed to liquid-phase sintering, lattice distortion-induced bond reconstruction, and reduced intrinsic loss from vibration mode splitting. Optimum microwave dielectric properties were obtained for the composition Mg 0.94 Cu 0.06 MoO 4 sintered at 800 °C for 6 h, ε r =6.86, Q× f =29,400 GHz, and τ f =-60.97 ppm/°C.