Improvement of superconducting properties of (Bi, Pb)-2223phase by TlF3 doping
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In this work, the superconducting properties of thallium fluoride (TlF3)doped Bi1.8-xTlxPb0.35Sr2Ca2Cu3 OyF3x(x=0-0.15)compounds are presented. The X-ray diffraction analysis shows that the proportion of (Bi, Pb)-2223phase is higher than the secondary (Bi, Pb)-2212 one in all samples and its highest value is about 82.74% for x=0.05. From the resistivity curves, the highest values of the onset critical transition temperature (T-c.on), the offset critical transition temperature (T-c.off) are seen for x=0.10. The calculation of activation energy (U-0) in the TAFF (thermally activation flux flow) region proves the positive effect of TlF3 doping on the dissipative behavior of energy near T-c.off. Flux pinning strength is enhanced by increasing TlF3 content up to x=0.10, and decreased by the application of a magnetic field. The other superconducting parameters like T(H-c2), T(H-irr), xi(0) and mu H-0(c2)(0) are also improved significantly by doping. The obtained results of Ac susceptibility measurements show that the onset temperature of diamagnetism is improved by TlF3 doping, in accordance with the resistivity results. (C) 2016 Elsevier B.V. All rights reserved.