STRUCTURAL CHARACTERIZATION OF R(2)CU(2)O(5) (R=YB, TM, ER, Y, AND HO) OXIDES BY NEUTRON-DIFFRACTION

The structural features of the R(2)Cu(2)O(5) family of compounds have been studied by high-resolution neutron powder diffraction. This isostructural series belongs to the noncentrosymmetric space group Pna2(1). A comparative study of the influence of the rare earth on the structural parameters is presented. In addition to the expected expansion of the RO(6) octahedra when the rare earth ionic radii are varied, the main modification of the structure corresponds to the elongation of the apical Cu-O distance in the CuO5 pyramid. Conversely, the basal plane remains unchanged. A systematic variation of the structural stability is found depending on the size of the rare earth atom. (C) 1995 Academic Press, Inc.