Effect of homovalent anion doping on the conductivity and phase transitions in Na2SO4

An attempt has been made to understand the effect of doping homovalent anio n dopants such as CO32-, B4O72-, MoO42-, and WO42- on the conductivity and phase transitions of Na2SO4 by means of XRD, DSC, and impedance measurement s. Our studies indicate that the observed conductivity enhancement is large ly due to an increase in the free volume in the structure. Apart from the s ize, the shape and orientational ordering of the dopant ion in the sulfate sublattice seem to influence the activation energy. The structure of the gu est anion appears to be one of the major factors determining the phase stab ilization of Na2SO4 (I) at low temperatures, (C) 1999 Academic Press.