LA2SRCU2O6 - NEUTRON-DIFFRACTION STUDY

The oxide La2-xSr1+xCu2O6 is one of the rare layered copper oxides which do not exhibit superconducting properties. In order to understand this behavior a detailed neutron diffraction study of La2SrCu2O6 was undertaken. This study confirms the preliminary X-ray diffraction investigation. However it allows several original features concerning the oxygen atoms to be observed: existence of vacancies in the O(1) sites corresponding to the basal planes of the CuO5 pyramids and of extra oxygen on the O(3) site located between the copper layers. An analysis of the anisotropic thermal parameters shows also anomalies of the anisotropic factors ß11 of O(2) and ß33 of O(1). These features are interpreted in terms of defects which tend to create a three-dimensionnal framework. Morever the examination of the interatomic distances shows that the intercalation of oxygen between the copper planes is really favoured in this structure owing to the bigger size of the cation interleaved between the copper layers compared to the calcium or yttrium in other layered cuprates. © 1990.