Substitution of 3-d Elements for Cu in High-Tc Superconductive Oxides

Abstract

Measurements of powder X-ray diffraction, superconducting transition temperature Tc and Mössbauer effect were performed from 4.2 K to 1000K for doped systems of La_1.85Ba_0.15(Cu₁-_xM_x)O_4-δ(LBCMO) and YBa₂ (Cu₁-_xM_x)O_7-δ (YBCMO) with M=Zn, Ga and all 3-d metal elements. In fact, Fe, Co, Ni, Zn and Ga could be substituted homogeneously for Cu at least up to 10% . For M = Fe, Co and Ga, phase transitions from the orthorhombic to tetragonal structure were found with increasing x in YBCMO. Across the structural transition, however, Tc decreases gradually with x and no anomalies were found. This suggests that the superconductivity occurs essentially in the 2-dimensional phane for both LBCMO and YBCMO.