• A P B Sinha

      Articles written in Bulletin of Materials Science

    • Studies on thick films of photoconducting cadmium sulphide

      D P Amalnerkar M S Setty N R Pavaskar A P B Sinha

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      Highly photosensitive films of CdS have been prepared using the thick film technique. The films obtained from the composition containing CdS-100, CdCl2−10 and CuCl2−0·05 parts by weight (reacted at 500° C) are found to give the best photosensitivity on firing at 600° C. The ratio of light to dark current ∼108–109 which is considerably higher than what is reported for thin films, single crystals and sintered layers. A strong chemisorption of oxygen is found to be responsible for high photosensitivity. The spectral response for doped CdS film is similar to that obtained for thin films, single crystals and sintered layers and also shows a red shift with increasing Cu concentration. However, the undoped CdS has a broad spectral response at room temperature ranging fromλ=550 to 690 nm; unlike the thin films and single crystals which give a sharp peak atλ=510 to 520 nm. A probable explanation has been suggested for this type of behaviour.

    • Superconductivity in compound Y1-2xCexBa2+xCu3O6·5+δ system

      M R Chandrachood I S Mulla M V Kuber A P B Sinha

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      Partial substitution of Ce in place of Y has been achieved by taking care of charge compensation and compounds with the general formula Y1-2xCexBa2+xCu3O6·5+δ have been successfully prepared. X-ray powder diffraction analysis reveals that this substitution gives orthorhombic single phase for 0⩽x⩽0·3. TheTc remains nearly unchanged between 94-90 K.

    • Low temperature preparation ofβ-alumina by an alkoxide route

      M K Dongare A P B Sinha

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      β-alumina has been prepared by the thermal decomposition of a mixture of sodium and aluminium isopropoxides followed by heating up to 1000°C. It has been found necessary to use sodium isopropoxide in excess (25–30%) for the complete formation ofβ-alumina at 1000°C. On the other hand one obtains a mixture ofβ-alumina andα-alumina when the starting materials are taken in the stoichiometric ratio Na2O:11Al2O3. DTA, TG and DTG studies of a mixture of sodium and aluminium isopropoxide showedβ-alumina formation at 1000°C.

    • Role of apex oxygen and redox elements in high temperature superconductors

      R E Amritkar D G Kanhere P V Panat A P B Sinha

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      The presence of valence fluctuating redox ions such as Pb, Tl, Sb, etc can enhance the transition temperature of the new oxide superconductors. We propose the possibility of the existence of negative Hubbard parameter (U) on redox ion which results in effective negativeU on apex oxygen bridging redox ion and the CuO2 planes. This enhancesTc.

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