Mechanisms affecting microwave dielectric properties of Li2Mg2TiO5 ceramics based on lithium excess

Abstract

Herein, the feasibility was assessed through first principles, and the effect of lithium excess on both the structure and dielectric properties of Li(1+x)2Mg2TiO5 (0.000 ≤ x ≤ 0.200) ceramics was investigated by solid-phase reaction method. An appropriate excess of lithium can moderately inhibit the volatilization of lithium and reduce the production of the secondary phase MgTi2O4, though it cannot completely inhibit its production. Li(1+0.050)2Mg2TiO5 exhibits the best dielectric properties with εr =14.55, Q × f =127,393 GHz (@9.6 GHz), and τf = −19.91 ppm/°C. The influence of non-inherent factors on the dielectric properties is dominant, with the increase in relative density to 93.53 % and the growth in average grain size to 28.67 μm contributing to the reduction of dielectric loss. The decrease in εr is due to the decrease in secondary phase content. Results from bond ionicity and Raman wavenumber variations in the intrinsic factors show that the intrinsic factors have little effect on the εr. Whereas, the increase in lattice energy as well as the decrease in FWHM contribute to the decrease in dielectric loss. In addition, a proper excess of lithium helps to increase the bonding energy thereby optimizing the temperature stability. The optimized Li(1+0.050)2Mg2TiO5 has great potential for application in microwave communications.