Crystal Structure of the Tetragonal Form of Ba2YCu3O7-x

The crystal structure of the high-temperature form of Ba 2 YCu 3 O 7- x was refined by the Rietveld analysis of TOF neutron powder diffraction data taken at 49 K. This compound is tetragonal with lattice constants a = 3.8533 Å and c = 11.7631 Å. It has an oxygen-deficient triperovskite structure, in which oxygen atoms on a z = 1/2 plane are missing, an oxygen site at (0, 1/2, 0) is about 9% occupied, and Ba 2+ and Y 3+ ions are completely ordered in a [Ba-Y-Ba] ∞ , sequence along the c axis.