Synthesis and Characterization of Tl-1223 Substituted by Scandium.

X-ray powder diffraction, scanning electron microscopy (SEM), energy dispersive X-ray, electrical resistivity and AC-magnetic susceptibility measurements have been performed for polycrystalline superconducting samples of type TlBa₂Ca_2−x Sc _x Cu₃O_9−δ (0.0 ≤ x ≤ 0.6). The powder X-ray diffractograms indicate that the tetragonal structure of Tl-1223 is not affected by Sc-substitution whereas the lattice parameters are changed. The X-ray analysis indicates that the low-contents of scandium (x) enhance the formation of Tl-1223 and reduce the secondary phases. The grain-size determined by SEM decreases as x increases. The electrical resistivity measurements show suppression in the superconducting transition temperature, T _c, and an increase in both the residual resistivity and the superconducting transition width as x increases. The suppression in T _c is attributed to the hole-filling mechanism. [ABSTRACT FROM AUTHOR]