Structure dependence of dielectric characteristics in Li2Mg3Ti1-x(Al0.5Ta0.5)xO6 ceramics

To investigate the effects of (Al0.5Ta0.5)4+ substitution on the crystal structure and dielectric characteristics of Li2Mg3TiO6, a set of Li2Mg3Ti1-x (Al0.5Ta0.5)xO6 (x = 0.0–0.12) samples were fabricated via solid-state process. XRD and Rietveld refinement results confirmed the formation of single rock salt structure in the space group Fm3m (No.225) within 0.0 ≤ x ≤ 0.12. Subsequently, some intrinsic factors were introduced to evaluate the structure dependence of dielectric characteristics in Li2Mg3Ti1-x (Al0.5Ta0.5)xO6 ceramics based on the unit cell parameters. The variation trend of dielectric constant (εr) was explained by the relative density and average ionic polarizability. The quality factor (Q × f) showed the same trend as the packing fraction and lattice energy, indicating the intrinsic lattice anharmonicity might play vital roles in dielectric loss. Additionally, the temperature coefficient of resonant frequency (τf) was strongly associated with the bond energy of Etotal. Typically, the Li2Mg3Ti0.91(Al0.5Ta0.5)0.09O6 sample obtained at 1310 °C possessed remarkable dielectric performances: εr = 15.06, Q × f = 169,600 GHz and τf = −27.45 ppm/°C.