STRUCTURAL DISORDERS IN THE SUPERCONDUCTING GASR2CA3CU4OY

Selected area electron diffraction (SAED) and high resolution transmis sion electron microscopy (HRTEM) studies were performed on the new sup erconductor GaSr2Ca3Cu4Oy (Ga-1234), n = 4 member of the homologous se ries CaSr2Can-1CunO2n+3 prepared under high pressure. Although it cons ists of rather irregular intergrowths of the blocks with n = 3, 4, and 5 [CuO2] layers, the average number of [CuO2] layers is close to 4. I n addition, an intralayer ordering between two different types of [GaO 4] tetrahedral chains along the b axis, as well as an interlayer disor dering of the chains along the c axis, are also observed. (C) 1996 Aca demic Press, Inc.