Impedance spectroscopy study and phase transition in phospho-vanadium mixed oxide LiZnV0.5P0.5O4

An X-ray crystallographic study has allowed us to identify a powder of the type LiZnV 0.5 P 0.5 O 4 , which contains 50% of vanadium and 50% of phosphore, inside the binary system LiZnVO 4 –LiZnPO 4 . The structure is isotypic with the phenacite like LiZnP0 4 . X-ray diffraction patterns are indexed according to the lattice parameters of the rhombohedral system and the R3 space group. IR spectra show the presence of VO 4 and PO 4 groups in the network of this material. The experimental results indicate that σ AC ( ω ) is proportional to ω n . The activation energy found from the Arrhenius plot confirms that the conduction processing of the material is not due to simple hopping mechanism. The temperature dependence of frequency exponent n was investigated to understanding the conduction mechanism in LiZnV 0.5 P 0.5 O 4 . The non-overlapping small Polaron tunneling (NSPT) model can explain the temperature dependence of the frequency exponent. A phase transition at T = 623 K has been evidenced by Differential scanning calorimetry (DSC) and subsequently confirmed by the analysis of dielectric and electric properties.