• H N Acharya

      Articles written in Bulletin of Materials Science

    • Photoelectronic properties of HgI2 crystals for nuclear radiation detection

      S L Sharma H N Acharya

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      Photoelectronic properties of red mercuric iodide single crystals, grown from its saturated solution in tetrahydrofuran, have been studied for the wavelength range 450-700 nm at temperatures 80, 110, 175, 235 and 300 K. Various aspects of the optical generation of charge carriers have been discussed. The computer simulation of the room temperature photoconductivity has generated the optimized values of the mobility-lifetime products (𝜇e𝜏e = 5.67 × 10-5 cm2/V, 𝜇h𝜏h = 0.18 × 10-5 cm2/V), and surface recombination velocities (𝑆e = 3.2 × 105 cm/s, 𝑆h = 4.5 × 105 cm/s) of the charge carriers in these crystals. The estimated values of the electron and hole drift lengths for typical electric fields suggest that, under the negative electrode illumination, THF 𝛼-HgI2 crystals have high potential as regards to their use as phptodetectors in most of the scintillation spectrometers.

    • Synthesis of Er3+ and Er3+ : Yb3+ doped sol–gel derived silica glass and studies on their optical properties

      Dipankar Mandal H D Banerjee M L N Goswami H N Acharya

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      Er3+ and Er3+ : Yb3+ doped optical quality, crack and bubble free glasses for possible use in making laser material have been prepared successfully through sol–gel route. The thermal and optical, including UV-visible absorption, FTIR etc characterizations were undertaken on the samples. The absorption characteristics of Er3+ doped samples clearly revealed the absorption due to Er3+ ions. On the other hand Yb3+ : Er3+ doped samples showed enhanced absorption due to ${}^{2}F_{7/2} \rightarrow {}^{2}F_{5/2}$ transition. The absorption and emission crosssection for ${}^{2}F_{7/2} \leftrightarrow {}^{2}F_{5/2}$ of Yb3+ were estimated. FTIR absorption spectra have clearly shown the reduction of the absorption peak intensity with heat treatment in the range 3700–2900 cm-1. The 960 cm-1 band also showed progressive decrease in the absorption band peak intensity with heat treatment. The result of the investigations with essential discussions and conclusions have been reported in this paper.

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