Zinc bismuth vanadate glasses with compositions 50V2O5-xBi2O3-(50-x) ZnO have been prepared using a conventional melt-quenching method and the solubility limit of Bi2O3 in zinc vanadate glass system has been investigated using x-ray diffraction. Density has been measured using Archimedes’ principle; molar volume (Vm) and crystalline volumes (Vc) have also been estimated. With an increase in Bi2O3 content, there is an increase in density and molar volume of the glass samples. The glass transition temperature (Tg) and Hurby coefficient (Kgl) have been determined using differential scanning calorimetry (DSC) and are observed to increase with increase in Bi2O3 content (i.e., x), up to x = 15, thereby indicating the structural modifications and increased thermal stability of zinc vanadate glasses on addition of Bi2O3. FTIR spectra have been recorded and the analysis of FTIR shows that the structure depends upon the Bi2O3 content in the glass compositions. On addition of Bi2O3 into the zinc vanadate system, the structure of V2O5 changes from VO4 tetrahedral to VO5 trigonal bi-pyramid configuration. The optical parameters have been calculated by using spectroscopic ellipsometry for bulk oxide glasses (perhaps used first time for bulk glasses) and optical bandgap energy is found to increase with increase in Bi2O3 content.
The ac conductivity of zinc modified tellurium based quaternary glasses having composition 60 TeO 2 -10 B 2 O 3 -(30 -x) Bi 2 O 3 -x ZnO; x = 10, 15, 20, 25 and 30 has been investigated in the frequency range 10 -1 -10 5 Hz and in temperature range 483-593 K. Frequency and temperature dependent ac conductivity found to obey Jonscher power law modified by Almond-West. DC conductivity, crossover frequency and frequency exponent have been estimated from the fitting of the experimental data of conductivity with Jonscher power law modified by Almond-West. The ac conductivity and its frequency exponent have been analyzed by various theoretical models. In presently studied glasses ac conduction takes place via tunneling of overlapping large polaron tunneling. Activation energy is found to be increased with increase in zinc content and dc conduction takes place via variable range hopping proposed by Mott with some modification suggested by Punia et al. The value of the stretched exponent (b) obtained by fitting of M 00 reveals the presence of nonDebye type relaxation. Scaling spectra of ac conductivity and electric modulus collapse into a single master curve for all compositions and temperatures, reveals the presence of composition and temperature independent conduction and relaxation process in these glasses. Activation energy of conduction (W) and electric modulus (E R ) are nearly equal, indicating that polaron have to overcome the same energy barrier during conduction as well as relaxation processes.
Zinc bismuth silicate glasses with compositions 40SiO 2 · xZnO · (60 − x)Bi 2 O 3 (x = 0, 5, 10, 15, 20, 25, 30, 35, and 40) have been prepared by conventional melt-quench technique and the solubility limit of zinc in bismuth silicate glass system has been estimated using X-ray diffraction technique. Density has been measured using Archimedes' principle; with increase in ZnO in the samples, the molar volume and density are found to decrease. The glass transition temperature (T g ) has been determined by using differential scanning calorimetry (DSC) and is observed to increase with increase in ZnO content. Raman and FTIR spectra have been recorded at room temperature and the analysis of Raman and FTIR shows that in all the glass compositions, asymmetric and symmetric stretched vibrations of Si-O bonds in SiO 4 tetrahedral units exist and with decrease in Bi 2 O 3 , the contribution of symmetric vibrations begins to dominate which results in increased compactness of the glass structure.
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