Sol-gel synthesis and characterization of β-MgSO 4 :Mg(NO 3 ) 2 –MgO composite solid electrolyte

Composite solid electrolytes in the system (1 − x )β-MgSO 4 :Mg(NO 3 ) 2 – x MgO with x = 0.1–0.6 (mole) were synthesized by sol-gel method and analysed by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, energy dispersive X-ray, Fourier transform infrared spectroscopy and alternating current impedance spectroscopy. Structural analysis showed solid-solid phase transformation from anhydrous MgSO 4 to β-MgSO 4 . Thermal study showed melting and decomposition of β-MgSO 4 at ∼1030 and ∼1114 °C, respectively, in all composite samples. Morphological analysis indicated crystalline and amorphous phases of particles with average size ranging from 0.1 to ∼5.6 μm. For samples with x ≥ 0.4, β-MgSO 4 crystals were not ordered and formation of a new MgO phase due to initial decomposition of β-MgSO 4 was observed. The conductivities of the composites were in the order of 10 −6 S cm −1 at room temperature and account from the formation of MgO···Mg 2+ species at the interface regions between β-MgSO 4 and MgO phases.