High T_c Superconductivities of A₂Ba₄Cu₆O_14+y

Abstract

Superconductivities of A2 2 Ba4 4 Cu 6 O 14+ y (0< y <2.5, A = lanthanides except for Pm) compounds are studied through X-ray powder diffraction pattern analysis and electrical resistance measurement. Resultant compounds in case of A = La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm and Yb except for Ce, Pr, Tb and Lu exhibit both characteristic diffraction patterns for A 2 Ba 4 Cu 6 O 14+ y , i.e., oxygen defect perovskite (GDP) and superconducting state. Key structure for realizing high Tc more than 90 K and narrow transition width is confirmed to be related with the GDP phase.