Abstract
Bulk superconductivity with T c (zero) up to 106 K in a Tl 0.5 Pb 0.5 Ca 0.8 Pr 0.2 Sr 2 Cu 2 oxide with Y 1 Ba 2 Cu 3 O y -like structure was observed. A single phase, tetragonal structure with a = 0.382 ± 0.001 and c = 1.200 ± 0.001 nm and space group P4/mmm, was found in Tl 0.5 Pb 0.5 Ca 0.8 Pr 0.2 Sr 2 Cu 2 oxide samples by X-ray diffraction. T c (zero)'s were found to be 78, 96, 106, 98, 45 and 25 K for Tl 0.5 Pb 0.5 Ca 1-x Pr x Sr 2 Cu 2 oxide samples with x = 0, 0.1, 0.2, 0.3, 0.5 and 0.7, respectively. For x = 1, the samples exhibited semiconducting behavior. All sintered samples were found to be remarkably homogeneous both in composition and structure. They were also exceptionally regular in microstructure and highly reproducible and stable. Although the six-metal blend makes the system appear to be rather complicated composition-wise, it is compensated by the relatively simple crystal structure. Furthermore, the preparation conditions are much less stringent than those for other copper-based high-T c superconductors. © 1989 Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division).