The effect of dielectric constant of the PbTiO3 dispersoid on the conductivity of Na2SO4 has been probed. At the Curie temperature, 490 degrees C, PbTiO3 undergoes ferroelectric to paraelectric phase transition followed by a sharp change in the dielectric constant. The Na2SO4-PbTiO3 composites have been prepared at two different temperatures, namely 600 and 900 degrees C. Compositions containing 5, 10, 20, 30, 40, 50 m% PbTiO3 have been investigated using Impedance Spectroscopy, Differential Scanning Calorimetry (DSC), X-ray diffraction (XRD) and Rietveld analysis. The series of compositions prepared at 900 degrees C exhibit a maxima in the conductivity for 20 m% PbTiO3. The composites prepared at 600 degrees C exhibit a peak in the conductivity at 20 m% PbTiO3 in addition to the percolation threshold at 40 m% PbTiO3. The enhancement in the conductivity by a factor of 40 at 300 degrees C has been observed for the system prepared at 600 degrees C while an enhancement in the conductivity by a factor of 8 at 300 degrees C has been observed for the System prepared at 900 degrees C. Further, the transition temperature of Na2SO4 remains unaltered for both series. A slight nonlinearity has been observed in the vicinity of the transition temperature of the dispersoid. (c) 2007 Elsevier B.V. All rights reserved.