PhysicaC 211 (1993) 29-35 North-Holland PHYSICA Sulphur-oxygen substitution in YBa2Cu306+xSy analyzed by means of X-ray emission spectroscopy Yu.M. Yarmoshenko, V.A. Trofimova, L.V. Elokhina and E.Z. Kurmaev Institute of Metal Physics, Russian Academy of Sciences- Ural Division, S. Kovalevskaya str. 18, 620219 Ekaterinburg GSP- 170, Russian Federation S. Butorin Department of Physics, Uppsala University, Box 530, S-751 21 Uppsala, Sweden R. Cloots S. U.P.R.A.S., Institute of Chemistry. B6, Universit~ de Liege, Sart Tilman, B-4000 Liege, Belgium M. Ausloos 1 S. U.P.R.A.S., Institute of Physics, B5, Universitd de Liege, Sart Tilman, B-4000 Liege, Belgium Received 29 December 1992 Revised manuscript received4 April 1993 The analysis of substitution effects upon doping of YBa2Cu306+~Sy by sulphur is given on the basis of the investigation of S Kay.2 and S KI31 X-rayemissionspectra. It is foundthat sulphur can enter the lattice of YBa2Cu307and substitute oxygen atoms. With increasingsulphur concentrationfromy> 0.5 to 2.0 S atoms form isolated sulphate groups which do not have a longorder but can be detected by X-rayemission spectroscopy. 1. Introduction One of the essential features of high-To supercon- ductors on the base of YBa2Cu306+x is the very strong sensitivity of their superconducting proper- ties to substitution of components by different ele- ments. It is well known that one can form many such compounds with partial or full substitution of Y by RE elements. Also Ba and Cu can be replaced by var- ious metallic ions. At the same time, the attempts to substitute oxygen by other chalcogens were not so successful. Several papers have reported the partial substitution of oxygen by fluorine. This leads to the instability of superconducting properties of the Y 123 phase [ 1 ]. In ref. [ 2 ] oxygen was substituted by sulphur in a solid phase reaction synthesis process by partial re- e-mail: u2150ma@bliulgl 1 .bitnet placement of CuO by CuS. According to X-ray dif- fraction analysis for samples with 20% substitution of CuO by CuS in the initial mixture, the ortho- rhombic phase of YBa2Cu307 type was dominant. Lattice parameters were weakly changed with sul- phur concentration, but the intensity of diffraction peaks ot the (00l) type was sharply increased. The cyclical heating of these samples led to Tc degrada- tion from 108 to 90 K. In ref. [3] Yl_zNdzBa2CuaO6+~Sy compounds were prepared by reaction of the initial Y1 _zNd~Ba2Cu306+x and pure sulphur in a vacuum sealed tube. The additional peaks were discussed in terms of the superstructure ordering of oxygen and sulphur atoms. These peaks were suggested to cor- respond to interatomic distance d= 8.2 ~ in the a- direction of the Y123 crystal structure. According to ref. [ 3 ] the samples contained mainly two phases: one made of panicles containing S and 0921-4534/93/$06.00 © 1993 ElsevierSciencePublishers B.V. All rights reserved.