Studies on Ag 2O.M xO y.TeO 2 (M xO y=WO 3, MoO 3, P 2O 5 and B 2O 3) ionic conducting glasses

Abstract

Similarities and differences between the electrical, thermal and spectroscopic characterization results obtained by partial replacement of TeO 2 by WO 3, MoO 3, P 2O 5 and B 2O 3 in the form of yAg 2O.(1− y)[ xM x O y .(1− x)TeO 2] system are reported. It has been observed that the compositional variation of glass transition temperature is linear for WO 3 and is non-linear for MoO 3, P 2O 5 and B 2O 3 substitutions. Constituent dependency of conductivity at ambient temperature shows two maxima for tungsto–tellurite, molybdo–tellurite and phospho–tellurite glass systems while only a single maximum is observed for boro–tellurite glasses. From the individual X-ray photoelectron spectral analysis, it is found that tungsten exhibits two oxidation states whereas molybdenum, phosphate and borate are not reduced. The non-bridging oxygen atoms are distinguished from that of the bridging oxygen atoms by deconvoluting the O 1s XPS spectra. Raman spectroscopy shows that besides the expected TeO 4 trigonal bipyramid, the TeO 3 trigonal pyramid, the tungsten and molybdenum tetrahedra, the tungstate and molybdate octahedra, phosphate tetrahedra and borate triangles and tetrahedra are also present in tungsto–tellurite, molybdo–tellurite, phospho–tellurite and boro–tellurite glasses, respectively. The intensity ratios of the Raman peaks ( I 780/ I 660) may represent the ratio of the fractions of TeO 3 tp and TeO 4 tbp: (TeO 3/TeO 4). A good agreement is found for the fraction of TeO 3/TeO 4 obtained from both Raman and XPS studies. These results are correlated with those from conductivity and T g studies. The unique crystallization behavior of these tellurite glasses were observed by the high temperature Raman spectral studies.