Effects of non-stoichiometry on the structural evolution, microstructure and dielectric properties of rock salt-type Li2Mg3SnO6 ceramics

The porous morphology and secondary phase originated from lithium evaporation have deteriorated dielectric properties of Li2Mg3SnO6 ceramic. To solve this issue, a set of non-stoichiometric Li2Mg3-2xSn1-xO6 (x = −0.04, −0.02, 0.00, 0.02, 0.04, 0.06) samples were prepared by the solid-state method. Subsequently, the effects of non-stoichiometry on the structural evolution, microstructure and dielectric properties of rock salt-type Li2Mg3-2xSn1-xO6 ceramics were investigated. The Rietveld refinement and SEM results confirmed that moderate non-stoichiometry could eliminate secondary phase and promote densification. For −0.04 ≤ x ≤ 0.04, the upward tendency of dielectric constant (εr) and quality factor (Q×f) was dominated by the improved phase purity and densification. As 0.04 ≤ x, the deterioration of dielectric characteristics was explained by the dielectric polarizability, lattice energy and packing fraction. The temperature coefficient of resonance frequency (τf) shifted from −36.41 to −27.23 ppm/°C, which could be attributed to the poor thermostability of Mg2SnO4 (τf = −64 ppm/°C) and enhanced octahedra bond energy