Phase Composition and Microwave Dielectric Properties of Li_2(1+x)Mg₃Ti₄O₁₂ Ceramics with Inverse Spinel Structure

In this work, non-stoichiometric Li_2(1+x)Mg₃Ti₄O₁₂ (L_xMTO, x = 0.00–0.05) ceramics with excess lithium were prepared through a simple reaction sintering route to suppress lithium volatilization. According to the characterization of the phase composition and microscopic morphology of the pellets, single-phase L_xMTO ceramics with a good microstructure were obtained. Excess lithium effectively inhibited the volatilization and optimized the morphology of the ceramics. A trend in relative density with an initial increase followed by a steep decrease was a predominant observation with the change in dielectric properties. The permittivity of the samples was dominated by the relative density and distortion of the [TiO₆] octahedron structure caused by Li⁺. The dielectric loss primarily originated from the refraction loss and scattering generated by pores, and the grain boundaries also contributed to the loss in the quality factor. Ultimately, at 1220°C, the Li_2.08Mg₃Ti₄O₁₂ ceramics exhibited excellent microwave dielectric properties: ε_r = 17.83, Q×f = 69,823 GHz and τ_f = −18.19 ppm/°C.