It has long been recognized that elemental doping is an effective way of stabilizing superconducting phase and raising T{c}. After extensive experiments, we synthesized and characterized a series of new superconducting cuprates by Mo-doping. Bulk thallium based superconductors withnominal starting composition of (Tl2-xMoxBa2Ca2Cu3Ox) were prepared through a solid-solid reaction technique. For this purpose a Ba-Ca-Cu-O precursor was preparaed by taking the stoichiometric amounts of BaCO3, CaCO3 and CuO with subsequent mixing and grinding followed by sintering at 850oC. Finally, appropriate amounts of MoO2 and Tl2O3 were added to the precursor and the whole mixture was calcined at 950oC under oxygen flow.Different phases including the high-Tc Tl-2223, Tl-2212, Tl-1223, Tl-1212 phases formed in the resulting compound were identified. Some other phases were also found when the Tl to Mo ratio was changed from 1.6: 0.4 to 1.4 :0.6 and 1 : 1 in Tl1.6Mo0.4Ba2Ca2Cu3Ox superconductor. From the resistivity measurements, the critical temperature Tc(0) for the compound was found to around 89 K. The enhanced doping of Molibdenum (Mo) in Tl-cuprates induces pairing mechanisms to occur outside the CuO2 layers and thus reducing high-Tc phase formation and hence the Tc(0) value.

Full text: IJEIR_1267_Final.pdf