Electrical transport studies in Na2O and Fe2O3 containing borate glasses.

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. [ABSTRACT FROM AUTHOR]