• Sudha Mahadevan

      Articles written in Bulletin of Materials Science

    • Elastic properties of As-Sb-Se glasses

      A Giridhar Sudha Mahadevan A K Singh

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      Results of measurement of elastic modulii on As-Sb-Se glasses are reported and their composition dependence discussed. The Young’s and the shear modulii lie in the range of 170–210 and 65–80 kb respectively. These values are typical of chalcogenide glasses. For (As, Sb)40Se60 glasses, the modulii increase monotonically with increasing Sb2Se3 content. The observed composition dependence of the modulii for the AsxSb15Se85 −x glasses is examined in terms of the chemically ordered structural units in the glasses.

    • Thermal expansion studies on As-Sb-Se glasses

      A Giridhar Sudha Mahadevan A K Singh

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      The results of measurement of thermal expansion coefficient from 50°C to the softening temperature on eight glass compositions of the As-Sb-Se system are presented. Measurements have been made on (As, Sb)40Se60 and AsxSb15Se85−x glasses at heating rates of 1°C/min and 5°C/min. The composition and temperature dependence of the thermal expansion coefficient is discussed in the light of results of other chalcogenide glasses.

    • Non-isothermal crystallization of As2Se3 glass

      A Giridhar Sudha Mahadevan A K Singh

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      The results of non-isothermal crystallization studies performed at different heating rates on batches of As2Se3 glasses prepared from melts at 400°C, 600°C and 800°C are reported. The peak temperature of crystallizationTp, the enthalpy of crystallization ΔHc and the activation energy for crystallizationEc are independent of the melt temperature used in the preparation. Bulk nucleation with three-dimensional growth of crystals is indicated for As2Se3. The values of ΔHc andEc are found to be respectively 23·3 ± 0·9 cal/g and 36·5 ± 0·9 kcal/mol for As2Se3.

    • DC electrical conductivity of some Cd-Ge-As glasses

      A Giridhar Sudha Mahadevan

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      Results of measurement of d.c. electrical conductivity σ from 85 to 550 K are reported for eleven glass compositions of the Cd-Ge-As system. Three regions are seen in theσ-T data of all these glasses. In region I (85 to 140 K),σ is essentially constant and independent of temperature. In region II (200 to 430 K),σ is thermally activated with a single activation energy. In region III (>430 K) a sudden increase is seen inσ with temperature. From an analysis of the results, it has been possible to identify the mechanism of hopping conductivity among localised ‘defect’ states with region I, normal band type conductivity due to carriers excited to the extended states with region II and thermally assisted memory switching with region III.

      In the composition dependence ofσ and ΔE for the CdGexAs2 glasses, special features are seen at the composition Cd28·57 Ge14·28 As57·15, which has equal mol fractions of CdAs2 and CdGeAs2. For the Cd2Ge-As glasses also, a maximum in ΔE and a minimum inσ are seen at this composition.

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