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 La 2 Mg(Mg 1/3 Sb 2/3 )O 6 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 La 2 Mg(Mg 1/3 Sb 2/3 )O 6 features a Debye-like behaviour, with a bulk conductivity, σ b , varying between 10 -7 -10 -4 S ‧cm -1 within 500–900 °C temperature range, and activation energy (E a ) of ∼ 1.36 eV. In addition, the microwave dielectric properties of La 2 Mg(Mg 1/3 Sb 2/3 )O 6 sintered at 1625 °C display optimized quality factor (Q× f ) of ∼ 28,700 GHz ( f = 9.65 GHz), a dielectric constant (ε r ) of ∼ 20.2 and temperature coefficient of the resonant frequency ( τ f ) of ∼ − 89 ppm/°C. This work widen the reduced number of A 3 + B 2 / 3 2 + B 1 / 3 5 + O 3 compounds explored so far.