The effects of partial substitutions of Zn and Fe on the Cu sites in LaBa 2 Cu 3 O 7±x , and a comparison with similar substitutions in YBa 2 Cu 3 O 7-x
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The structural effects of Zn and Fe substitutions in LaBa 2 Cu 3 O 7-x have been examined using time-of-flight neutron powder diffraction, and compared with previous data relating to similar studies of YBa 2 Cu 3 O 7-x . Although the Fe and Zn ions display a similar site preference (for Cu(1) and Cu(2), respectively) in both systems, significant structural differences have been found. In particular, higher concentrations of dopant are possible in LaBa 2 Cu 3 O 7±x (up to 25% Cu replacement by Zn and 66% replacement by Fe), and superconductivity is rapidly destroyed due to the incorporationof additional structural defects. For Zn substitutions, a significant concentration of vacancies on the O(4) sites is introduced, whereas Fe substitutions result in a gradual increase in structural disoder of a more general type. Evidence for this disorder is found on both the oxygen sublattice, e.g. partial filling of sites in the La plane at z = 1 2, and the cation sublattice, with some intermixing of the La and Ba ions.
|Number of pages||10|
|Journal||Physica C: Superconductivity and its Applications|
|Publication status||Published - 10 Nov 1991|