Conference Papers

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Subject: search.filters.subject.Activation energy

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    Preparation of vacuum deposited cadmium selenide thin films for optoelectronic applications
    (Elsevier Ltd, 2016) Santhosh, T.C.M.; Bangera, K.V.; Shivakumar, G.K.
    Cadmium selenide is a direct band gap material which finds applications in optoelectronic devices. Preparation of the compound semiconductor in thin film form with stable electrical characterization has been investigated in the present study. As deposited films at room temperature (25°C) are non-stoichiometric with excess cadmium and films grown at 180°C substrate temperature are stoichiometric and homogeneous. The crystallinity increases with increase in substrate temperature. The optical band gap determined from absorption measurements lie in the range 1.89 eV - 2.02 eV. Electrical conductivity measurements made in a temperature range from 25°C to 200°C yield thermal activation energy of 0.52eV for stoichiometric films. Films deposited at 180° C and annealed at 200° C for two hours are found to be stabilized in its electrical and structural properties. © 2016 Elsevier Ltd.
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    Thermal stability and crystallization kinetics of Bi doped Si15Te85-xBix (0 ≤ x ≤ 2) chalcogenide glassy alloys
    (Elsevier Ltd, 2018) Fernandes, B.; Munga, P.; Ramesh, K.; Udayashankar, N.K.
    Bulk Si15Te85-xBix (0 ≤ x ≤ 2) chalcogenide glassy alloys were prepared by well-established melt quenching technique. Thermal stability and crystallization kinetics of these alloys were investigated by employing differential scanning calorimetry (DSC) technique at different heating rates, namely, 10, 15, 20 and 25 K/min under non-isothermal condition. Thermal parameters such as glass transition (Tg), onset crystallization (Tc) and peak crystallization (Tp) temperatures were observed. Double crystallization peaks observed in the DSC thermogram refer to the instability and phase separated network in the glasses. Various kinetic parameters such as thermal stability (ΔT), enthalpy (ΔHc), entropy (ΔS), specific heat (ΔCp) and fragility index are deduced. The calculated kinetic parameters suggest that the stability of glassy samples decreases with the increase in Bi addition. The activation energies of glass transition (Eg), and crystallization (Ec) are calculated using relevant kinetic formulae. We further discuss on the kinetics of the synthesized materials relevant for their applications in phase change memory (PCM) material. © 2017 Elsevier Ltd.
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    Structural and electrical behaviour of glass ceramic 00B under sandwiched condition between two Crofer22APU substrates
    (Elsevier Ltd, 2020) Bhattacharya, S.; Shashikala, H.D.
    Obtaining high temperature glass and glass ceramic based seals is one of the biggest challenges in the present day fabrication of Solid Oxide Fuel Cell (SOFC) stacks. Formation of BaCrO4phase in BCAS glasses leads to degradation of cell performance. This work focusses on one glass composition derived from a BCAS species named 00B which is free of BaO and Al2O3contents. 00B was sandwiched between two Crofer22APU plates forming CGC sandwiches and heated for repeated thermal cycles from RT to 800 °C to check their compatibility with the metallic substrate. Microscopic images of the CGC interface and XRD data of the internal glass surface of the broken sandwich were recorded to observe the structural properties of the prepared sandwich. DC resistivity measurements of the glass under sandwiched conditions between two Crofer22APU plates, at RT and at elevated temperatures were carried out, to determine its resistivity at high temperatures, under SOFC operating conditions. The CGC sandwiches prepared using sample 00B showed good structural properties after repeated thermal cycles and sufficiently high specific resistance at room and elevated temperatures. The 00B glass without BaO and Al2O3content, but having structural and electrical behaviour suitable for coating on Crofer22APU, is suggested to be a potentially promising candidate for SOFC sealant applications. © 2020 Elsevier Ltd. All rights reserved.