• S G Sathyanarayan

      Articles written in Pramana – Journal of Physics

    • Electrical conductivity and stimulated thermocurrent studies in dicalcium lead propionate single crystal

      V Madhusudan S G Sathyanarayan G Sivarama Sastry

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      Electrical conductivity and stimulated thermocurrent (stc) studies are carried out in dicalcium lead propionate (dlp) in pure, Cu2+, Fe3+ and acetate doped single crystals over a temperature range of 303° to 503° K. Conductivity measurements on pure and doped single crystals ofdlp indicate that both propionate anions and metallic cations are responsible for the transition occurring at 333°K. Thermoelectric power measurements from 340° to 500°K indlp (pure) indicate that the transport charge carriers are electrons. A model for the conduction mechanism is proposed on the basis of hopping ofπ or resonating electrons of carboxyl groups through tunnel paths involving metal ions (Pb2+ and Ca2+). From activation energies estimated from conductivity andstc measurements, thestc peak indlp (Fe3+) occurring at 513°K is attributed to impurity vacancy jump mechanism.

    • Transport properties and thermal studies on pure and Cu2+-doped potassium hydrogen maleate single crystals

      A D Reddy S G Sathyanarayan G S Sastry

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      Conductivity, thermally stimulated depolarisation (tsdc) and thermal studies are carried out on pure and Cu2+-doped potassium hydrogen maleate single crystals. Bothdta anddsc reveal first-order phase transition at 503 K.dsc further shows that the crystal decomposes even before the transition is complete. A ‘knee’ is observed around 505 K in conductivity plots at this transition. Thetsdc of Cu2+-doped system gave a single peak at 241 K and the reasons are analysed. Activation energies from conductivity andtsdc suggest proton conduction. However no direct evidence in coulometric experiment could be observed. But thermoelectric power measurements reveal the charge carriers to be positive.

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