Effect of phase composition on the crystal structure and microwave dielectric properties of ZnMg2TiO5 ceramics

Novel microwave dielectric ceramics ZnMg₂TiO₅ were synthesized by traditional solid-state method. Crystal structure refinement, transmission electron microscopy (TEM), and Raman spectroscopy reveal the coexistence of a secondary phase, MgO, with the predominant cubic spinel phase (Fd-3m) in ZnMg₂TiO₅ ceramics. The ceramics with dense microstructures exhibit excellent microwave dielectric properties at 1260 °C: ε_r = 15.6, Q×f = 92,899 GHz (at 10.8 GHz), and τ_f = −56.9 ppm/°C. The content of MgO, driven by thermodynamic factors, influences significantly impact the microstructure and microwave dielectric properties of the ceramics, particularly inducing the generation of localized lattice distortions and the formation of dislocations. The ε_r follows the same trend as the molecular polarizability of the actual individual crystal cells. Notably, a near-zero τ_f (−7.4 ppm/°C) was realized by two-phase composites and excellent comprehensive properties were obtained (ε_r = 17.9, Q×f = 57,546 GHz).