In this study, the electrical conductivity of the Na2SO4-Na2WO4 system has been measured using complex impedance technique to investigate the effect of anion substitution on the cationic conductivity. In the Na2SO4(I) based solid solubility region the conductivity increases as SO4 ions are substituted by WO4 in the crystal structure. Maximum conductivity of 4x10-4 Scm-1 with an activation energy 0.5 eV at 450oC has been observed around 22 mol% Na2WO4. The secondary conductivity maximum observed at 48 mol % Na2WO4 could be associated with a two-phase mixture consisting of Na2SO4 based and Na2WO4 based solid solutions.
