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|Title:||Study of ionic conductivity in KBr: (CrO4)2- crystals|
Kumar, N Vasanth
Reddy, A Ramachandra
|Abstract:||The ionic conductivity of pure KBr and KBr crystals doped with chromate anion has been measured in the temperature range of 200-600oC. In pure KBr crystals, large contribution to conductivity by cation vacancies has been observed at higher temperatures. Ionic conductivity measurements are made on pure KBr crystals and KBr crystals doped with 0.25, 0.5 and 0.75 mole % of chromate anion in as-grown state. Further, the effects of quenching and annealing on conductivity of KBr crystals doped with 0.75 mole % chromate ion are measured. The conductivity versus temperature plots show that, as concentration of impurity anions increases, the conductivity decreases in extrinsic associated region. As the concentration increases to 0.75 mole %, the conductivity increased to high value compared to 0.5 mole %. But, it is less than that of pure crystals. The extrinsic un-associated region shows a slight variation in conductivity but, tends to be same that of as-grown pure KBr crystals. The variation in conductivity of doped KBr crystals are explained on the basis of formation of complexes with background impurities, formation of neutral pairs, introduction of fresh dislocations, etc. The variation in conductivity due to quenching and annealing is explained on the basis of dissociations and aggregation of complexes, vanishing of newly introduced dislocations, etc. The corresponding activation energy values are evaluated.|
|ISSN:||0975-1041 (Online); 0019-5596 (Print)|
|Appears in Collections:||IJPAP Vol.40(12) [December 2002]|
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