Structural and ion transport properties of Na₂Mg₂TeO₆ and Na₂NiMgTeO₆ solid state electrolytes

Two solid state compounds of the family of Na₂Mg₂TeO₆ (M=Mg,NiMg) were synthesized through conventional solid-state reaction method. Structural properties of the samples were characterized by means of powder X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy techniques. The XRD results reveal the well-known hexagonal layered P2-type as a major crystalline structure. SEM images showed the shapes of grains of the both samples appear relatively similar; the size of the grains of Na₂NiMg₂TeO₆ is smaller than that of Na₂Mg₂TeO₆. FTIR reveals the possible stretching and bending vibration modes of Te-O and metal oxides. AC impedance spectroscopy used to investigate the ion transport properties of the solid electrolytes. The electrical properties of materials were investigated by using brick layer model. Also, the influence of temperature in ionic conductivity of Na₂M₂TeO₆ (M = Mg, NiMg) is analyzed