• S K Arora

      Articles written in Bulletin of Materials Science

    • Flux growth and habit modification of CaWO4 crystals

      S K Arora R S Godbole Tomy Abraham

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      The poor quality of natural scheelite necessitates growing these crystals in the laboratory. The flux growth method has been modified to obtain crystals of better quality. Various habits of the grown crystals are reported. The effect of the growth conditions like temperature, cooling rate, charge composition, etc. to yield different morphology has been investigated.

    • Crystal growth of barium molybdate by flux evaporation

      S K Arora G S Trivikrama Rao

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      Single crystals of BaMoO4 have been grown by isothermal evaporation of lithium chloride at 700°C. The morphology and mechanism of growth of the crystals have been discussed. The quality of the crystal has been assessed by selective etching.

    • Kinetics of calcium molybdate crystallization

      N M Batra S K Arora

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      Kinetics of crystallization of calcium molybdate from unstirred molten solutions of lithium chloride of low to medium supersaturation in platinum crucibles by the process of continuous cooling at 5° C hr−1 from temperaturesT0=700 and 750°C are investigated. The crystal size measured by optical microscopy for different crystallization periods reveals that both crystal length and width generally increase with cooling period. The degree of crystallizationαt,also increases with cooling period, attaining a maximum of 0·90. The diffusion rate constants,KDlat 700 and 750°C are 0·0776 and 0·1138 respectively. The effect of variation of the crystallization temperature on the crystal size and their number is also studied.

    • Josephson effects and dc SQUID behaviour in break junction of Y-Ba-Cu-O at 77 K

      S K Arora A K Gupta Neeraj Khare N D Kataria G S N Reddy V N Ojha V S Tomar

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      Break junctions of Y-Ba-Cu-O superconductor were realized by creating fresh crack in the bar shape bulk samples mounted in a specially designed probe kept in the liquid nitrogen bath. While the bulk sample was kept static, a sharp tip of a shaft was moved downward from the outside of the dewar in order to break the sample. It was possible to change the critical current of the break junctions by adjusting pressure on the tip of the shaft. The effects of magnetic field and microwave power on the I-V characteristic of the junction were studied. The junction was found to show periodic V-B behaviour and the microwave-induced Shapiro steps were clearly observed at 77 K. The flux noise spectrum of the junction was also studied.

    • Performance of a 2-hole Y-Ba-Cu-O rf SQUID

      S K Arora A K Gupta Neeraj Khare V S Tomar V N Ojha

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      A two-hole rf SQUID has been fabricated out of bulk YBCO by drilling two holes and careful erosion of the wall between the holes. Commercial SQUID electronics is inductively coupled to the SQUID through a copper coil glued in one of the holes. Periodic oscillations in V-B characteristic of the SQUID are observed at 77 K. The spectral density of the flux noise in the white noise region is 5·5 × 10−4Φ0 / √Hz. The flux noise is frequency-dependent below 200 Hz.

    • CVT growth of zirconium sulphoselenide single crystals

      S G Patel S K Arora M K Agarwal

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      Large single crystals of a few important members (x=0, 1, 2) of the series ZrSxSe2−x compounds have been obtained by chemical vapour (iodine) transport method. The crystals have been characterized for several properties. Their semiconducting nature is inferred from resistivity vs temperature measurements, their optical absorption data reveal indirect gap transitions, their thermoscans indicate their stability over a limited temperature range, and they essentially grow by the mechanism of two dimensional layer propagation.

    • 1/f Noise properties of swift heavy ion irradiated epitaxial thin films of YBCO

      S K Arora Ravi Kumar D Kanjilal G K Mehta S Khatua R Pinto Vijay Kumar A K Gupta

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      Effect of 250 MeV107Ag ion irradiation induced columnar defects on the noise properties of the YBCO superconductor in the normal and superconducting state have been investigated. Magnitude of the spectral density of the noise is found to scale inversely with the frequency and exhibit a quadratic dependence on the bias current confirming that the noise arises due to the resistance fluctuations. The magnitude ofSv has been found to decrease with decrease in temperature and shows a noise peak in the transition region. The noise performance of these materials in the vicinity of the superconducting transition as well as in the normal state is found to improve by an order of magnitude after irradiation with 250 MeV107Ag ions. The decrease in the magnitude of 1/f noise peak is due the irradiation induced enhanced flux pinning of the material which suppresses the flux motion induced noise in the vicinity ofTc.

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