Studies on Ag2O.MxOy.TeO2 (MxOy = WO3, MoO3, P2O5 and B2O3) ionic conducting glasses

Similarities and differences between the electrical, thermal and spectrosco pic characterization results obtained by partial replacement of TeO2 by WO3 , MoO3, P2O5 and B2O3 in the form of yAg(2)O.(l - y)[xM(x)O(y).(1 - x)TeO2] system are reported. It has been observed that the compositional variation of glass transition temperature is linear for WO3 and is non-linear for Mo O3, P2O5 and B2O3 substitutions. Constituent dependency of conductivity at ambient temperature shows two maxima for tungsto-tellurite, molybdo-telluri te and phospho-tellurite glass systems while only a single maximum is obser ved for boro-tellurite glasses. From the individual X-ray photoelectron spe ctral analysis, it is found that tungsten exhibits two oxidation states whe reas molybdenum, phosphate and berate are not reduced. The non-bridging oxy gen atoms are distinguished from that of the bridging oxygen atoms by decon voluting the O 1s XPS spectra. Raman spectroscopy shows that besides the ex pected TeO4 trigonal bipyramid, the TeO3 trigonal pyramid, the tungsten and molybdenum tetrahedra, the tungstate and molybdate octahedra, phosphate te trahedra and berate triangles and tetrahedra are also present in tungsto-te llurite, molybdo-tellurite, phospho-tellurite and boro-tellurite glasses, r espectively. The intensity ratios of the Raman peaks (I-780/I-660) may repr esent the ratio of the fractions of TeO3 tp and TeO4 tbp: (TeO3/TeO4). A go od agreement is found for the fraction of TeO3/TeO4 obtained from both Rama n and XPS studies. These results are correlated with those from conductivit y and T-g studies. The unique crystallization behavior of these tellurite g lasses were observed by the high temperature Raman spectral studies. (C) 19 98 Published by Elsevier Science B.V. All rights reserved.