Crystal structure, Raman spectra, infrared spectra and microwave dielectric properties of Li2Mg3Ti1-X(Mg1/3Ta2/3)XO6 (0 ≤ x ≤ 0.2) solid solution ceramics

Highlights: • Microwave properties of ε_r = 14.70, Q·f = 200,600 GHz and τ_f = −11.83 ppm/°C were obtained. • A small amount of (Mg_1/3Ta_2/3)⁴⁺ can obviously improve properties. • Rietveld refinement and spectra were used to analyze properties. • Relationships between intrinsic parameters and properties were established. - Abstract: Li₂Mg₃Ti_1-X(Mg_1/3Ta_2/3)_XO₆ (x = 0.00, 0.05, 0.10, 0.15, 0.20) solid solution ceramics were prepared by the conventional solid-state reaction method. Rietveld refinements, Raman spectra, infrared spectra, polarizability and bond energy were used to research the changes of microwave dielectric properties of these solid solutions. With the increase of x values from 0 to 0.2, dielectric constants (ε_r) gradually increased, which could be explained by the variations of the polarizability, infrared resonant modes and Raman vibration modes. The variations of the quality factor (Q·f) could be explained by the changes of the bond valences. The temperature coefficient of resonant frequency (τ_ƒ) correlated with the bond energy of TiO bonds. A small quantity of (Mg_1/3Ta_2/3)⁴⁺ can obviously improve the microwave dielectric properties. Excellent microwave dielectric properties of ε_r = 14.70, Q·f = 200,600 GHz and τ_f = −11.83 ppm/°C were obtained for Li₂Mg₃Ti_0.95(Mg_1/3Ta_2/3)_0.05O₆ ceramic sintered at 1550 °C.