Abstract
The structure of PbBaYSrCu 3O 7 has been determined by neutron and X-ray powder diffraction using a profile analysis method. The symmetry is tetragonal with space group I4 mm and cell parameters a = 3.8436(1) Å and c = 27.426(1) Å. The structure of this oxide is built up from the intergrowth of single rock salt layers with triple perovskite layers. The perovskite layer is oxygen deficient and perfectly ordered according to a sequence of one layer of Cu 1O 2 sticks and two layers of CuO 5 pyramids. The ordering of copper and lead on two different sites is demonstrated, showing definitively the existence of a perfectly ordered “0223” type structure, contrary to the existence of mixed lead/copper layers proposed by previous authors. The oxygen distribution and coordination of lead and copper are compared to those observed for Pb 2Sr 2YCu 3O 8 and PbBa 0.8Sr 1.2PrCeCu 3O 9.
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