Crystal structure, electric and microwave dielectric properties of La2Mg(Mg1/3Sb2/3)O6 novel double-perovskite with non-stoichiometric 1:1 cationic ordering

In this contribution, the novel double-perovskite La2Mg(Mg1/3Sb2/3)O6 has been successfully prepared by solid-state reaction method, and its structure has been determined for the first time by a combination of X-ray and neutron powder diffraction data analysis. The novel material exhibits a thermal expansion of ∼9.1 ppm/°C and a large optical band gap (4.23 eV). The complex impedance data analysis indicates that La2Mg(Mg1/3Sb2/3)O6 features a Debye-like behaviour, with a bulk conductivity, σb, varying between 10-7-10-4 S ‧cm-1 within 500–900 °C temperature range, and activation energy (Ea) of ∼ 1.36 eV. In addition, the microwave dielectric properties of La2Mg(Mg1/3Sb2/3)O6 sintered at 1625 °C display optimized quality factor (Q×f) of ∼ 28,700 GHz (f = 9.65 GHz), a dielectric constant (εr) of ∼ 20.2 and temperature coefficient of the resonant frequency (τf) of ∼ − 89 ppm/°C. This work widen the reduced number of A3+B2/32+B1/35+O3 compounds explored so far.