A neutron diffraction study of the system Y1-yCayBa2-yLayCu3O7-x

Abstract

The series Y_1-yCa_yBa_2-yLa_yCu₃O_7-x, which is structurally related to YBa₂Cu₃O_7-x, is of particular interest since the co-substitution of Ca (for Y) and La (for Ba) is electrically self-compensating. Seven samples with yc decreases with increasing y. At higher values of y, only La enters the structure. The resulting charge imbalance is compensated by the introduction of additional oxygen and T_c remains approximately constant. The changes in T_c cannot simply be related to the Cu oxidation state, i.e. hole density in the Cu(2)O₂ layers.