Transport, magnetic and structural properties of (Tl0.5Pb0.5)Sr2-xCexCa2Cu3Oy compounds

Resistivity, DC magnetization and x-ray diffraction measurements were perfo rmed on 6 sample with nominal composition (Tl0.5Pb0.5)Sr2-xCexCa2Cu3Oy, wit h x =0.0, 0.1, 0.2, 0.3, 0.4 and 0.5. As cerium content was increased, the transition temperature increased up to about 6 Ii when x=0.1. The phase dia gram of the onset transition temperature versus Ce content reflects the exp ected behavior as the hole concentration in the Cu-O planes is expected to decrease with increasing x, passing from overdoped through optimally doped to an underdoped state for higher values of Ce4+ replacing Sr2+ atoms. Magn etization measurements at 4 Ii, in cyclic field +/- 9 Tesla, on the other h and, showed that the critical current density of the samples decreased as C e content was increased for ail values x. Tt also showed the existence of t he superconducting phase up to x=0.5, which was not detectable by resistivi ty measurements. X-ray diffraction measurements, indicate that Ce enters th e structure of the Tl-1223 phase, and hence affect its superconducting prop erties as it changes the charge carrier concentration in the Cu-O planes.