• Volume 18, Issue 1

      February 1995,   pages  1-97

    • Foreword

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    • A first principles technique for the analysis of alloy phase stability in random binary alloys

      A Mookerjee

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      In this communication we introduce the augmented-space recursion method coupled with the orbital peeling technique, as a powerful tool for the calculation of effective cluster interactions, useful for the study of alloy phase stability. An application to the well studied PdV system has been carried out.

    • Conducting glasses

      C S Sunandana

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      Ion-conducting tellurite glasses are built from trigonal bipyramidal TeO4 units. Neutron diffraction as well as Raman and IR spectroscopic studies have shown that there is a continuous transition from TeO4 → TeO3+1 → TeO3 as the alkali oxide content is progressively increased, non-bridging oxygens being created in the process. Electrical conduction in both single and mixed alkali tellurite glasses is satisfactorily explained by the interchange transport mechanism, based on the site-memory effect exhibited by the glass network.

    • Some aspects of glass-ceramic superconductors

      B K Chaudhuri

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      In this review article we have discussed, in brief, the general procedure for making glass-ceramic superconductors and some of their physical properties. All these glasses which become superconductors after properly annealing at higher temperatures are, in general, transition metal oxides (TMO) with copper ions. So the usual theoretical models of polaronic hopping conduction mechanisms are valid for explaining the semiconducting behaviour of these oxide glasses. Some of the transport properties of the glass-ceramic (GC) phases, viscosity of the glassy state, wire making feasibility etc have also been discussed in short.

    • Sol-gel glasses: some recent trends

      D Ganguli

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      The basic experimental steps in the preparation of sol-gel glass as developed in recent times, and their relevance have been discussed taking high purity silica glass as an example. Current developments in sol-gel derived ultra-low expansion glasses, rare earth doped laser glasses, semiconductor-doped non-linear glasses, gradient index lenses, microoptics and organic molecule-doped (mainly dyes) glasses for sensor and other applications have been discussed in brief.

    • Glass formation domains and structural properties of nonconventional transition metal ion glasses

      A Ghosh

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      Glass formation domains and structural properties of some binary transition metal ion glasses based on nonconventional network formers Bi2O3 and PbO have been investigated. With the same network former, the glass formation domains depend on the transition metal ions. Homogeneous glasses with random network structure were obtained, as evidenced by the composition dependent density, molar volume and glass transition temperatures. Significant information about possible structural units in these glasses has been obtained from the IR spectra of these glasses.

    • Ultrasonic velocity and attenuation in glass

      U S Ghosh

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      Ultrasonic velocity and attenuation in glasses exhibit anomalous properties and the current theory most successful in explaining these anomalous properties in the high temperature range has been presented. The model considers that the disorder inherent in amorphous network results in a double well potential corresponding to two equilibrium configurations and a particle is ascribed to move in the double-well potential. Acoustic behaviours in glasses have been interpreted in terms of a thermally activated relaxation process. Improvement of this basic model has also been discussed. Mention has also been made of some behaviours at high temperature that need further research for convincing explanation.

    • Crystallographic and electrical study of the chromium substituted ferrous zinc copper ferrites

      V M Nanoti D K Kulkarni

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      The structural and electrical properties of the oxidic spinel Zn0·5Cu0·5FexCr2−xO4 (x=0·8, 0·9, 1·0, 1·1) have been investigated through X-ray diffraction, electrical resistivity, and thermoelectric measurements.

      X-ray diffraction data showed formation of single spinel phase with cubic structure. D.C. resistivity measurements from room temperature to 850 K was carried out and activation energy for all the compositions evaluated. Thermoelectric measurements showedp-type semiconducting nature in all the samples.

    • Microstructural features of Cd0·8Zn0·2Te thin films studied by X-ray diffraction and electron microscopy

      B Samanta U Pal B K Samantaray T B Ghosh S L Sharma A K Chaudhuri

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      Thin films of synthesized Cd0·8Zn0·2Te have been deposited on glass substrate at different substrate temperatures. Different microstructural parameters like crystallite size, rms strain, dislocation density, stacking fault probability and stacking fault energy are determined by XRD, SEM, TEM and TED. XRD and XPS have been used to determine the composition. Variations of the microstructural parameters with film thickness and substrate temperature have been studied in order to obtain optimum growth condition for maximum particle size and least microstructural defects. An effort has been made to correlate the experimental results.

    • Dielectric measurements in vanadium doped barium titanate

      A Hanumaiah T Bhimasankaram S V Suryanarayana G S Kumar

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      Ceramic samples of Li0·1Ba0·95(VxTi1−x)O3, wherex=0 to 0·2 were prepared by solid state reaction method. The samples were characterized by XRD. The dielectric measurements have been carried out on the sintered disks as a function of the frequency (100 Hz-1 MHz) and temperature (300–420 K). The variation of dielectric constant with temperature indicates a diffuse phase transition in all the samples studied.

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