Structure and ionic transport studies of sodium borophosphate glassy system

Sodium borophosphate glasses of composition (mol%) 50Na(2)O-50[xB(2)O(3)-(1-x)P2O5], 0 less than or equal to x less than or equal to 0.8 have been prepared by melt quenching method and characterized through XRD, DSC, FTIR and impedance spectroscopy techniques. The glass transition temperature increases with the substitution of B2O3 due to the cross-linking of the network and the FTIR study shows the presence of different structural units in the network. The ionic conductivity study as a function of composition of B2O3 shows increment in conductivity with two conductivity maxima at 10 and 30 mol% of B2O3 and conductivity variations with temperature follow an Arrhenius type behaviour. Transport numbers evaluated for ions and electrons show that Na+ ions are the mobile species in the investigated systems. The frequency dependence of the electric conductivity follows a simple power law feature. The analysis of various electrical parameters as a function of temperature in different complex planes shows that the charge transport occurs by the hopping mechanism. (C) 2004 Elsevier B.V. All rights reserved.