SUPERCONDUCTIVITY IN (LA2-XYX)BA-2(CAYCU4-Z SYSTEM(Y)O)

The structural and superconducting properties of single phase (La2-xYx )Ba-2(CayCu4+y)O-z (0.0 less than or equal to x less than or equal to 0.5, 0.0 less than or equal to y less than or equal to 1.0) compounds with tetragonal triple perovskite structure are investigated using X-r ay diffraction, resistivity and oxygen content measurements. Samples w ith 0 less than or equal to x less than or equal to 0.5 and 0 less tha n or equal to y less than or equal to 1.0 are superconducting. increas ing y = 2 x, both the hole concentration in the Cu2O layers and T-c(R= 0) increases to a maximum value of 0.349 and 78 K at x = 0.4 and y = 0 .8, respectively. A correlation between the T-c and hole concentration seems to hold. (C) 1998 Elsevier Science B.V. All rights reserved.