Formation of Tl-1212 Phase in CR Substituted (Tl_1-xCr_x) Sr₂CaCu₂O₇ Superconductor

Superconducting samples of (Tl_1-xCr_x) Sr₂CaCu₂O₇ for x = 0.0-0.7 have been prepared by a solid state reaction technique at normal pressure using high purity elements. The powder X-ray diffraction patterns have been studied for samples. All samples showed the Tl-1212 as the major phase and Tl-1201 as the minor phase. The superconducting transition temperature Tc has been determined from the electrical resistivity measurements. The data of Tc, for (Tl_1-xCr_x) Sr₂CaCu₂O₇ show enhancement in its value from 104 K to112 K as x (Cr-content) increases from 0.7 to 0.1. Our results shows the highest onset temperature for x = 0.2-0.3 and the lowest temperature for x = 0.7.