• K N Madhusoodanan

      Articles written in Pramana – Journal of Physics

    • Thermal diffusion near glass transition in Ge-Se glasses measured by photoacoustics

      K N Madhusoodanan Jacob Philip

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      The glass transition in GexSe1−x) (0·1 ⩽x ⩽ 0·25) glasses has been investigated using the photoacoustic (PA) technique. It is found that the PA amplitude and phase undergo anomalous changes at the glass transition temperatureTg. The amplitude has critical minimum and phase has maximum values atTg. The variation of the thermal diffusivity, determined by measuring the frequency dependence of the PA amplitude and phase, with temperature shows sharp decrease near the glass transition temperature. The temperature dependence of the optical energy gap also has been measured and it shows a decrease with temperature for all compositions, the rate of decrease being higher for temperatures greater thanTg.

    • Composition dependence of the energy gap and thermal diffusivity in bulk As-Se glasses

      K N Madhusoodanan Jacob Philip

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      We have measured the composition dependence of the optical energy gap and thermal diffusivity in bulk AsxSe1−x (0.10⩽x⩽0.50) glasses using photoacoustic technique. The energy gap shows a threshold minimum value and thermal diffusivity has a threshold maximum value at the stoichiometric composition As2Se3 corresponding tox=0.40. The decrease in energy gap is explained on the basis of chemical bonding. It is argued that the threshold percolation of rigidity in the random network is responsible for the peaking of the thermal diffusivity at the stoichiometric composition.

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