Improvement of superconducting properties of (Bi, Pb)-2223phase by TlF3 doping

Abstract In this work, the superconducting properties of thallium fluoride (TlF 3 )doped Bi 1.8− x Tl x Pb 0.35 Sr 2 Ca 2Cu3 O y F 3 x ( 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)-2212one 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 TlF 3 doping on the dissipative behavior of energy near T c.off . Flux pinning strength is enhanced by increasing TlF 3 content up to x =0.10, and decreased by the application of a magnetic field. The other superconducting parameters like T ( H c 2 ), T ( H irr ), ξ(0) and μ 0 H c 2 (0) are also improved significantly by doping. The obtained results of Ac susceptibility measurements show that the onset temperature of diamagnetism is improved by TlF 3 doping, in accordance with the resistivity results.