Phase Composition and Microwave Dielectric Properties of Li2(1+x)Mg3Ti4O12 Ceramics with Inverse Spinel Structure

In this work, non-stoichiometric Li 2(1+ x ) Mg 3 Ti 4 O 12 (L x MTO, 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 x MTO 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 [TiO 6 ] 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 2.08 Mg 3 Ti 4 O 12 ceramics exhibited excellent microwave dielectric properties: ε r  = 17.83, Q × f  = 69,823 GHz and τ f  = −18.19 ppm/°C.