Impedance spectroscopy analysis of LiZnVO4 and LiMgVO4

A comparative LiZnVO₄ and LiMgVO₄ conductivity study was done from room temperature to 500 °C and at frequencies from 42 to 1 MHz. The impact of moisture absorption to the materials’ conductivity was investigated. It was shown for LiZnVO₄ that moisture absorption is responsible for the decrease of the compound’s conductivity as the material is heated up to 150 °C. The LiZnVO₄ bulk activation energy value was calculated to be 1.20 eV. Two grain boundary activation energy values were calculated for the LiZnVO₄, 0.59 eV at the lower temperature range and 1.37 eV at the higher temperature range. An explanation for the existence of these two values was given. Both materials’ plots of the loss factor (tanδ) versus frequency at different temperatures were found to display a peak, and the modulus master curves present a scaling behavior that suggests non Debye type conductivity relaxation and ion migration via hopping.