Neutron structure investigation of Ca2Y2Cu5O10

Abstract

Ca2Y2Cu5O10, a calcium yttrium cuprate, is the yttrium rich endmember of a homologous series of compounds with composition (Ca1-xYx)4Cu5O10 (0<x<0.5) [1]. According to the chemical formula the formal charge of copper can be varied between +2 and +2.4. The structure is incommensurate and related to the structure of NaCuO2 [2]. In both case the central structural elements are one dimensional Cu-O chains. According to the x-ray experiments we found a Ca/Y disorder. Instead of having 5 Na and 5 Cu positions in the quintupled supercell in the case of NaCuO2 there are 4 Ca/Y and 5 Cu positions in the supercell of Ca2Y2Cu5O10. Therefore Ca/Y positions and Cu-O chains have to be rearranged and distorted. Single crystals were grown in an optical floating zone furnace and were examined by single crystal diffraction experiments (x-ray and neutron scattering). Structure refinement was done with Shelxl-97 [3] (supercell: P21/c, a=5.4730(10)A, b=6.1801(10)A, c=14.081(2)A, β=104.550(14)°, z=2) and 3+1dimensional with Jana2000 [4]. As a result of the neutron experiment we got the cell metrics of both composite parts and the associated q vectors. One can describe one composite part as P21/c(α0λ)00 (a=5.474(5)A, b=6.181(9)A, c=2.,818(7)A, β=104.87(15)°), the other one as P21/m(α0λ)0s (a=5.458(5)A, b=6.181(9)A, c=3.523(9)A, β=104.24(15)°). The associated q vectors are (-0.0177 0 0.8) and (0.0221 0 1.25). On the poster a detailed description of the contents of the composite parts, positions of the atoms and distortion of the Cu-O chain will be given.