An X-ray Powder Diffraction Study of Sr2LnTaCu2O8, Ln = Nd, Sm, Eu, Gd

A series of oxides of the composition Sr2LnTaCu2O8, Ln = Nd, Sm, Eu, Gd has been prepared and characterized by X‐ray powder diffraction. Samples are tetragonal, space group P4/mmm and isostructural with a perovskite‐like phase Ba2LaTaCu2O8. The unit‐cell parameters have been determined using Mo or Si as internal standard. The structure of Sr2SmTaCu2O8 has been refined by the Rietveld method. X‐ray diffraction patterns of the samples and the crystal structure of Sr2SmTaCu2O8 showed ordering of Ta and Cu ions: the octahedrally coordinated Ta ion is on the Cu(1) site, while Cu ions remain on the Cu(2) sites of the Ba2YCu3O7−δ‐type structure. (Powder Diffraction File Nos. 46–1490 for Sr/NdTaCu2O8, 46‐1489 for Sr2SmTaCu2O8, 46‐1488 for Sr2EuTaCu2O8 and 46‐1487 for Sr2CdTaCu2O8.