The study of phase transition has been done in the temperature range 500 K to the melting point of the studied materials of the systems (1-x) Li3PO4 : x Li3VO4 with x = 0.0, 0.33, 0.50, 0.67 and 1.0 and Li3PO4 : x Li3VO4 with x = 0.0, 0.33, 0.50, 0.67, 1.0, 1.5 and 2.0. The molar magnetic susceptibility xM and dielectric constant (K) measurements have been performed for the study of phase transition. At phase transition materials under go from normal to superionic phase. An anomaly appears in xM and log K vs temperature (T) plots at phase transition. This is also reflected in electrical conductivity (s) and Seebeck coefficient (S) studies. All the studied material remains diamagnetic throughout the measurement.