Relation of Structure and Superconductivity in Self-Compensating Y_1-xCa_xBa_2-xLa_xCu₃O_y

The self-compensating compound of Y_1-xCa_xBa_2-xLa_xCu₃O_yis synthesized through a solid-state reaction method with x from 0.25 to 0.55. Structural and superconducting properties have been
investigated by x-ray diffraction, Rietveld refinement, and dc magnetization measurement, respectively. The impure peaks appear when x is more than 0.5 in the diffraction pattern. Orthorhombic--tetragonal transition occurs at x=0.45. Some local structural parameters, such as Cu(1)--O(4), Cu(2)--O(4) bond lengths, change randomly in a narrow range. The relationship between the character of (Ba/La)--O plane and T_c is rather interesting. We attribute the behaviour of superconductivity to the joint effects of these local structural parameters. The results give the evidence that the influence of the structural change on superconductivity is essential and independent of carrier concentration.