Electrical transport studies in Na2O and Fe2O3 containing borate glasses

Abstract

A new series of (X) Na2O.(0·5−x)Fe2O3.(0·5)B2O3 of sodium and iron oxides doped borate glasses were synthesised by melt quenching. The bulk density, structural and temperature dependent electrical properties of these glasses have been investigated. The density decreased with increase in Na2O content up to Na2O=0·2 and increased thereafter. The FTIR studies indicated the presence of BO3 and BO4 groups in the network and also has shown presence of minimum NBOs at x=0·2. These results are attributed to the significant structural modifications taking place in the glass network at Na2O=0·20. The dc electrical conductivity decreased with increase in Na2O content up to Na2O=0·20 and increased for further addition of Na2O. The activation energy has increased up to 0·2 mol% of Na2O and decreased thereafter. Based on these results, it is established that at x=0·20, a changeover of dc conduction mechanism predominantly from polaronic to ionic is taking place. Mott’s SPH, Mott’s VRH and Greave’s VRH models have been used to explain the high and low temperature conductivities.