• T N Sairam

      Articles written in Bulletin of Materials Science

    • 57Fe Mössbauer and positron lifetime studies of Al-Cu-Fe quasicrystals

      C M Chittaranjan T N Sairam K P Gopinathan C S Sundar

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      Al61·4Cu22·7Fe15·9, Al63·2Cu21·8Fe15 and Al71Cu14Fe15 have been studied by Mössbauer, positron annihilation and X-ray diffraction techniques. The positron lifetime, measured as a function of temperature, in Al61·4Cu22·7Fe15·9 shows a two-step increase. This is found to be due to the dynamics of phasons associated with Al and Cu, having activation energies of 0·43 eV and 0·78 eV respectively. In the case of Al71Cu14Fe15, a phase transformation from the quasicrystalline-crystalline phase at ≈ 550°C is observed.

    • Mössbauer and XRD studies on the effect of doping iron in KCaY(PO4)2

      T N Sairam G V Narasimha Rao B Viswanathan

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      The effect of doping iron at the yttrium site in hexagonal KCaY(PO4)2 is studied for various concentrations ofx (0≤x≤1), of iron using Mössbauer and X-ray diffraction methods. For low iron concentrations, very little changes in structure are seen but atx≈0·1, onset of new peaks in the XRD pattern is observed. The Mössbauer study of the doped samples reveals that iron has a solubility of up to 2·5% in the parent phase with any excess iron precipitating out to form a new and unknown phase. From a detailed analysis of the X-ray diffraction pattern (corresponding tox=1) of the latter phase, it is found that this phase is rhombohedral with the possible space groupR3.

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