• R Singh

      Articles written in Bulletin of Materials Science

    • Studies on Bi-Sr-Ca-Cu-O glasses and superconducting glass ceramics

      R Singh E Zacharias

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      Bi-Sr-Ca-Cu-O glasses and glass ceramics of various compositions were synthesised. The glass transition temperature varies from 396 to 422°C depending on the glass composition. The bulk glass ceramics of 4334, 4336, 2223 and 4246 compositions show superconductivity when the corresponding glass samples were heat-treated in air at 820°C for 3, 9, 12 and 24 h respectively. X-ray diffraction studies show that the superconducting phase present in all these compositions is Bi2Sr2Ca1Cu2Ox. The 4334 glass ceramic is almost a single-phase material with a preferred orientation such that thec axis is normal to the sample surface. The 2223 glass ceramic has a higherTc (onset) than the other three compositions indicating the presence of highTc phase (110K) also. ESR studies on the glass samples indicate the existence of Cu2+. The effect of heat treatment on ESR shows that the intensity of resonance decreases with increase in heat-treatment duration. This effect is more pronounced for the 4334 and 2223 compositions. The advantages of synthesizing superconducting materials by glass route are discussed in view of practical applications.

    • Some new results in porous silicon

      V K Jain Amita Gupta C R Jalwania Adarsh Kumar G K Singhal O P Arora D S Ahuja P P Puri R Singh M Pal

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      Efforts have been made to see the effect of some standard microelectronic processing steps on porous silicon. Our diffusion experiments for making p-n junctions confirm that this material can withstand high temperatures of the order of 800°C to 1000°C. A new technique for photolithography has been suggested to obtain porous silicon in selected areas. Etch stop method to control the thickness of the porous layer and an organic protective layer for porous silicon have also been suggested. Models proposed by other workers to explain luminescence in porous silicon are not sufficient to explain many experimental observations. A hybrid model is suggested.

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