• Volume 15, Issue 5

      August 1992,   pages  389-479

    • Foreword

      P Rama Rao K J Rao D Chakravorty H S Maiti

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    • Developments in ferroelectric ceramics for capacitor applications

      Dhananjai Pandey A P Singh V S Tiwari

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      A brief overview of the materials and processes for making ceramic capacitors based on BaTiO3 and relaxor ferroelectric compositions is presented with special emphasis on more recent developments.

    • Preparation and characterization of non-random YBa2Cu3O7-Ag composite

      B Srinivas G V Subba Rao

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      Silver addition to the highTc superconductor, YBa2Cu3O7 (YBCO) is known to improve its mechanical properties and critical current (Jc) characteristics. We have synthesized the superconductor-metal composite YBCO-Ag by an electroless process at room temperature (using sucrose or hydrazine hydrate in an alkaline medium). The latter method produces a non-random coating whereby each grain of YBCO is coated uniformly by silver. The intrinsic highTc of 90 K of YBCO can be recovered by compaction of the composite and subsequent heat treatment (900°C and 600°C) in oxygen.

    • Nanocomposites

      D Chakravorty

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      Nanocrystalline metals having sizes of the order of a few nanometres dispersed in an oxide glass matrix have been discussed in this review. The various physical and chemical routes developed so far for synthesizing such materials have been described. The different physical properties, especially optical, electrical and magnetic behaviour of these nanocomposites have been delineated. The physical mechanisms which give rise to these characteristics are discussed.

    • Sol-gel processing of materials for electronic and related applications

      D Ganguli

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      Various techniques of sol-gel processing for the preparation of electronic and related materials are described and reviewed. Typical examples are chosen from thin films and coatings of gels, crystalline materials and glasses as also bulk glasses to illustrate the variations in processing parameters and material properties.

    • Current trends in applications of magnetic ceramic materials

      D Bahadur

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      Magnetic oxides, a major constituent of magnetic ceramic materials, are most extensively used in a variety of applications as soft, moderate and hard ferrites. I review here its applications with special emphasis on some recent developments in magnetic recording materials.

    • Mutual phase stabilization of aluminium phosphate and titania in AlPO4-TiO2 binary system

      R Debnath J Chaudhuri

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      Crystallization behaviour of amorphous aluminium phosphate (AlPO4) and titania (TiO2) in a mixed system of the two (5:1) has been reviewed in the light of our recent results. The polymorphous aluminium phosphate in such a binary system grows exclusively in a single phase over a temperature range 500–1150°C. The phase is reported to have a tridymite-like structure belonging to orthorhombic system with cell parametersa=9·638±0·0019,b=8·664±0·0017 andc=18·280±0036Å. Titania in the system preferentially retains its anatase phase morphology up to a temperature (950°C) well beyond its normal anatase → rutile transformation temperature showing a phenomenon of stabilization of this phase in such mixture. An interfacial reaction mechanism that can explain the observed phenomenon of mutual phase stabilization has been discussed and implications of this result towards the use of such technique for stabilization of various polymorphous compounds in a single phase has been pointed out.

    • A novel technique for the preparation of fine ceramic oxides

      Amita Pathak P Pramanik

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      In this paper, we put forward a novel and simple chemical route for the preparation of fine ceramic oxides i.e. ferrites using triethylammonium carbonate as the precipitating agent. The particles were studied and characterized by X-ray diffraction and scanning electron microscopy. The emphasis is on the superiority of this technique over other chemical and conventional routes.

    • Sol-gel preparation of silica glass

      D Kundu G De B Karmakar A Patra D Ganguli

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      This paper is a preliminary report on the preparation of silica glass containing very low amount of hydroxyl by the sol-gel processing technique. Gels were prepared from optimized amounts of tetraethyl orthosilicate, fumed silica and water. Acids and bases in small quantities were added for catalysing hydrolysis and adjusting the pH. Dried gels were heated up to 1400°C in various atmospheres to obtain transparent silica glass of the required density and very low (<5 ppm) hydroxyl content.

    • Insulating ZnO film on silicon for MIS application

      A Dutta S Basu

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      High resistive zinc oxide thin film (∼ 0·5 µm) was deposited on single crystalp-silicon (100) wafers by an inexpensive spray-CVD method and was characterized both optically and electrically. Al/ZnO/Si (MIS) device structure was subsequently fabricated and bothI − V andC − V characteristics were studied. The semiconductor-insulator interface charge density (Dit) was calculated by Terman method and was found to be 3·85 × 1011 cm−2eV−1.

    • Lithium borosulphate glasses: an analysis of glass transition temperature results

      P R Gandhi V K Deshpande K Singh

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      Lithium borosulphate glasses have been prepared in three different series: (a) (42·5 −x)Li2O:57·5 B2O3:xLi2SO4; (b) 42·5Li2O: (57·5 −x)B2O3:xLi2SO4 and (c) 42·5Li2O:57·5B2O3:xLi2SO4. The glass transition temperature (Tg) of these glasses has been analysed on the basis of the fraction of four coordinated boron which governs the glass structure. The analysis reveals that the addition of Li2SO4 in series (a) and (b) gives rise to increased value of N4 whereas, in series (c) it increases the number of non-bridging oxygens.

    • Nickel silicide contact for silicon solar cells

      S Bandopadhyay U Gangopadhyay K Mukhopadhyay H Saha A P Chatterjee

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      Electroless nickel metallization on textured front surface is carried out to fabricate large area (13%) efficient silicon solar cells. It is established through XPS analysis that NiSi is formed at the front grid contact on the texturized surface at relatively low temperature leading to a low value of series resistance of the solar cells.

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      Posted on July 25, 2019

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