Impedance, dielectric and modulus study of Ti-doped LiSn2(PO4)3

Abstract

LiSn2(PO4)3 of composition LiSn1.85Ti0.15(PO4)3 with NASICON structure was prepared by solid-state synthesis. XRD results show the formation of stable phase material of rhombohedral structure with the R3 ̅c space group. Traces of unreacted SnO2 and minor impurity of SnP2O7 were detected. Impedance and dielectric study in the microwave range show conductivity enhancement in bulk and grain boundary. The room temperature ionic conductivity is 4.74x10-5 S/cm and the conductivity at 740 K is 2.37x10-3 S/cm. The highest value of dielectric constant ε' obtained is 2000 and the lowest value is 500. Imaginary modulus vs temperature plot indicates the presence of temperature relaxation in the material. The plot of relaxation frequency at different temperatures was used to calculate the activation energy which was found to be 0.23 eV. These imply that the material could be applied as solid electrolyte at high temperatures.