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

Abstract

An X-ray crystallographic study has allowed us to identify a powder of the type LiZnV0.5P0.5O4, which contains 50% of vanadium and 50% of phosphore, inside the binary system LiZnVO4–LiZnPO4. The structure is isotypic with the phenacite like LiZnP04. 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 VO4 and PO4 groups in the network of this material. The experimental results indicate that $$\sigma_{\text{AC}}$$ ( $$\omega$$ ) is proportional to $$\left( {\omega^{n} } \right)$$ . 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 LiZnV0.5P0.5O4. 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.