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Single-Crystal Structural Study of La2Cu0.95Li0.05O4.
Published online by Cambridge University Press: 28 February 2011
Abstract
A large crystal of flux-grown La2CuO4, examined through single-crystal neutron diffraction, was found to have an orthorhombic superstructure derived from the K2NiF4 structure type with a=5.359(1), b=5.363(1), c=13.127(2) Å. The pattern of systematically absent intensities indicated space group Pccn but meaningful refinement of thermal vibration parameters could not be obtained in this symmetry. Systematic examination of all possible orthorhombic subgroups of Fmmm yielded satisfactory refinement to R(F2)=2.57% only in space group Bmab. Incorporation in the crystal of Li derived from the flux results in an orthorhombic distortion smaller than found for pure La2CuO4. Refinement of the Cu site occupancy provided Cu0.95Li0.050(3), in excellent accord with a bulk chemical analysis. Reflections which violate the systematic absences of Bmab are attributed to a smaller volume fraction of domains in orientation twinned by 90° rotation about c. This interpretation is supported by transmission electron microscopy which revealed intergrown lamellae. Dark field imaging with a forbidden reflection illuminated only the twin lamellae.
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- Copyright © Materials Research Society 1988
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