Nb Substituted Cu0.5Tl0.5Ba2(Ca3Nb1)Cu5O_{14-delta} and Cu0.5Tl0.5Ba2(Ca4Nb1)Cu6O_{16-delta} Superconductors |
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Authors: | Nawazish A. Khan Arshad Hussain |
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Affiliation: | 1. Materials Science Laboratory, Department of Physics, Quaid-i- Azam University, Islamabad, Pakistan
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Abstract: | The effects of higher electro-negativity Nb substitution on the Ca site in Cu0.5Tl0.5Ba2 (Ca3Nb1)Cu5O $_{14-delta}$ and Cu0.5Tl0.5Ba2(Ca4Nb1)Cu6O $_{16-delta}$ superconductors have been investigated. The Nb doping has been found to increase the oxygen contents in Cu0.5Tl0.5Ba2O $_{16-delta}$ charge reservoir layer of the final compound. The post-annealing in the N2 atmosphere has been found to improve the superconducting properties; however, O2 annealing produced the material with inferior superconducting properties. The quantity of diamagnetism is increased with post-annealing in the nitrogen atmosphere; as N2 annealing helps in the formation of material with optimum carriers concentration in the CuO2 planes, which is done by the change in the charge state of thallium from Tl3+ to Tl1+. The Nb substitution has been found to develop the higher CuO2 planner phases such as Cu0.5Tl0.5Ba2Can ?2Nb1Cun 2 n+4?δ (n=5,6) with enhanced T c's. |
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