Superconductivity and structural changes in Y sub(0.8)Ca sub(0.2)Ba sub(2-x)Nd sub(x)Cu sub(3)O sub(y) cuprates with x less than or equal to 0.50

摘要

Nd doped Y sub(0.8)Ca sub(0.2)Ba sub(2-x)Nd sub(x)Cu sub(3)O sub(y) YBNCO compounds with x less than or equal to 0.50 have been prepared by the solid state reaction technique. The structure and the superconductivity for YBNCO compounds are characterized. The zero resistance transition temperature T sub(c0) for each sample was measured. T sub(c0) increases with the increase of the content of Nd in YBNCO as x less than or equal to 0.15, and decreases as x greater than or equal to 0.20. X-ray diffraction studies show that there is no structural phase transition in the whole doping range. The dependencies of the lattice constants and some other structural parameters on the content of Nd for the samples YBNCO with x less than or equal to 0.20 have different behaviour than that for the samples with x greater than or equal to 0.25. It seems that the superconductivity of YBNCO is related to the structural changes due to Ca and Nd co-doping.