The structural effects of Na and Ca substitutions on the Y site in YBa2Cu3O7-x
- 1 June 1989
- journal article
- Published by IOP Publishing in Superconductor Science and Technology
- Vol. 2 (1) , 5-8
- https://doi.org/10.1088/0953-2048/2/1/002
Abstract
On the basis of powder XRD data successful substitution of Na for Y in YBa2Cu3O7-x could not be achieved. For Ca substitutions, however, single phase materials were obtained at doping levels up to 20% with Tc decreasing to 80 K. The charge balance mechanism and resultant structural changes have been investigated using thermal analysis and powder neutron diffraction. The principal effects of Ca substitution appear to be a reduction of oxygen content in the basal plane of the unit cell, and shifts of Ba and O ions to compensate the effective transfer of positive charge from the Y sites to the basal plane. Similar, but smaller, displacements of Cu2 result in a decrease in the Cu2-Cu2 distance.Keywords
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