Elemental Substitution at Tl Site of Tl(1−x)X(x)(Ba, Sr)CaCu(2)O(7) Superconductor with X = Cr, Bi, Pb, Se, and Te

The effects of elemental substitutions at the Tl site of a Tl(1−x)X(x)(Ba, Sr)CaCu(2)O(7) superconductor with X = Cr, Bi, Pb, Se, and Te were investigated. This study aimed to determine the elements that enhance and suppress the superconducting transition temperature of the Tl(1−x)X(x)(Ba, Sr)CaCu(2)O(7) (Tl-1212) phase. The selected elements belong to the groups of transition metal, post-transition metal, non-metal, and metalloid. The relationship between the transition temperature and ionic radius of the elements was also discussed. The samples were prepared by the solid-state reaction method. The XRD patterns showed a single Tl-1212 phase was formed in the non- and Cr-substituted (x = 0.15) samples. The Cr-substituted samples (x = 0.4) showed a plate-like structure with smaller voids. The highest superconducting transition temperatures (T(c onset), T(cχ′), and T(p)) were also achieved by the Cr-substituted samples for x = 0.4 compositions. However, the substitution of Te suppressed the superconductivity of the Tl-1212 phase. J(c inter) (T(p)) for all samples was calculated to be in the range of 12–17 A/cm(2). This work shows that substitution elements with a smaller ionic radius tend to be more favorable in improving the superconducting properties of the Tl-1212 phase.