Physica C 185-189 (1991) 553-554 North-Holland lqllW Structural and Mrssbauer studies in REBaCuFeOs+ x compounds. M.Pissas, C.Mitros, G.Kallias, V.Psyeharis, D.Niarchos, A.Simopoulos,A.Kostikas, C.Christides +, K.Prassides+. Institute of Materials Science N.C.S.R. Demokritos, 153 10 Ag.Paraskevi Attikis GREECE. +School of Chemistry and Molecular Sciences, University of Sussex Falmer Brighton 9Q J, U.K. We have studied the non superconducting phase REBaCuFeOs+ x (where RE=rare earth), with neutron, x-ray powder diffraction and Mrssbauer spec- troscopy. 1. Introduction The oxygen deficient perovskite YBaCuFeOs+ x was isolated for the first time by L.Er-Rakho et al1. Recently, Meyer et al 2 pre- sented M~ssbauer spectra which revealed the existence of a single Fe 3+ site and concluded that only the (lbl) site is occupied with iron whereas (lbz) is occupied with copper. De- tailed analysis with M'rssbauer spectroscopy in the same series for RE=Y,Nd,Sm,Cd,Dy,Lu and Tm has been presented by M.Pissas et al3 . 2.Results and discussion We have performed Rietve!d refinements fer all our x-ray diffraction profiles in space group P4mm using the site lb I (z=0.27) for the iron and site lb 2 (z=0.74) for copper, with excellent results. RB-factors, for example, for Sm and Nd compounds are 3.43% and 6.51%, correspond- ingly. Figure 1 shows the dependence of the lattice constants and the extra oxygen in rela- tion with rare earth. 3.92 3.90 ,-,3.88 .( 03.86 3.84 3.P,2 0.08 A I Y 0.17 A 7.74 8 A X f7.72 ' r a [] a ~7.70 032 a D C ~ ~7.68 A • 0.11 • -= ~7.64 0.07 A 0.08 [~7.62 A I t t £ I ~7.60 Nd Sin Gd Oy Trn Lu Figure 1. Lattice constants and additional oxygen content vs lanthanide supporting cation in ReBaCuFeOs+x. Figure 2 shows part of Neutron diffraction pro- files of YBaFeCuOs+x from 320-500K. The mag- 0921-4534/91/$03.50 © 1991 - Elsevier Science Publishers B.V. All fights reserved.