Effect of Ce substitution on the properties of Tl-based superconductors

Samples with nominal composition (Tl0.5Pb0.5)Sr2-xCexCa2Cu3Oy were prepared with x in the range 0 to 0.5, to investigate the role of charge carrier concentration on the superconducting properties of Tl-based materials. The behavior of the normal state resistivity with temperature showed that as x changes from 0 to 0.2, the material moves towards optimally doped state. For higher Ce content the normal state resistivity versus temperature, started deviating from linearity. The onset transition temperature increased gradually by about 6 K as x was increased from 0 to 0.2. The zero resistance transition temperature rapidly decreased for samples with x > 0.2. Furthermore, XRD analysis revealed that Ce enters the structure of both Tl-1223 and Tl-1212. These results are discussed in terms of controlling the hole concentration in the CuO2 planes through Ce4+ replacement of Sr2+