X-Ray and Electron Microscopic Study of a High Temperature Superconductor Y_0.4Ba_0.6CuO_2.22

Abstract

A superconducting oxide Y 0.4 Ba 0.6 CuO 2.22 with T c higher than 88 K was synthesized. The crystal structure was found to be a derivative of the perovskite structure with orthorhombic unit cell dimensions of a =3.818 (1) Å, b =3.888 (1) Å, c =11.667 (4) Å, and V =173.19 (8) Å 3 . Basic unit cell of the cubic perovskite structure was tripled along the c axis, probably due to the ordering of Y 3+ and Ba 2+ ions and/or of oxygen vacancy. Apparent short bond length for Cu-O may partly be explained by oxygen vacancy amounting to a quarter, but the observed high T c suggests actual contraction of Cu-O bonds.