Influence of Zn substitution on the crystal structures and microwave dielectric properties of Li2(Mg1-xZnx)3TiO6 (0≤x≤0.2) ceramics

A series of Zn-doped Li2(Mg1-xZnx)3TiO6 (x = 0, 0.05, 0.10, 0.15, 0.2) ceramics were formed via the conventional solid-state process. Influence of Zn2+ on the crystal structures, phase compositions, sintering characteristics and properties of Li2(Mg1-xZnx)3TiO6 (0 ≤ x ≤ 0.2) ceramics were systematically studied. XRD results showed that a single phase with the cubic rock-salt structure was formed for Li2(Mg1-xZnx)3TiO6 (0 ≤ x ≤ 0.15) and the second phase of Zn2TiO4 could be detected with a further increase of the Zn2+ contents. Some intrinsic parameters were calculated in order to investigate the correlations between these parameters of Mg/Zn–O bonds and microwave dielectric properties. As the Zn2+ content increases, optimum Εr values exhibited an increasing trend, which could be explained by the variations of the polarizability and bond ionicity of Mg/Zn–O bonds. The decrease of maximum Q·f values for Li2(Mg1-xZnx)3TiO6 (x = 0, 0.05, 0.10, 0.15, 0.2) ceramics could be predicted by the decrease of the packing fraction and lattice energy of Mg/Zn–O bonds. τƒ values showed close relationship with the bond energy and thermal expansion coefficient of Mg/Zn–O bonds. Excellent combined microwave dielectric properties with Εr = 15.46 (at 10.9 GHz), Q·f = 125,453 GHz (at 8.6 GHz) and τf = −32.35 ppm/°C were obtained for Li2(Mg0.85Zn0.15)3TiO6 ceramic sintered at 1600 °C. © 2018 Elsevier B.V.