Synthesis and characterization of Sr1-xLnxCoO3-δ, Ln = Y, Srn-Tm, 0.1≤x≤0.5

Different perovskite-related phases have been found in an X-ray powder diffraction (XRD) and transmission electron microscopy study of the Sr(1-x)Ln(x)CoO(3-delta), Ln = Y, Sm-Tm, 0.1 less than or equal to x less than or equal to 0.5 systems. For the compositions Sr0.7Ho0.3CoO3-delta; Sr1-xEuxCoO3-delta, 0.3 less than or equal to x less than or equal to 0.4; Sr1-xGdxCoO3-delta, 0.3 less than or equal to x less than or equal to 0.5; Sr1-xTbxCoO3-delta, 0.3 less than or equal to x less than or equal to 0.4; Sr1-xDyxCoO3-delta, 0.2 less than or equal to x less than or equal to 0.3 the formation of phases isostructural with the recently discovered perovskite related Sr0.7Y0.3CoO2.62, a approximate to 2 x a(per), c approximate to 4 x a(per) (a(per) perovskite subcell) was observed. The crystal and magnetic structures of Sr0.7Dy0.3CoO2.62 were refined using neutron diffraction data (I4/mmm, a = 7.6280(8), c = 15.338(2) Angstrom, R-p = 0.0332, R-F(2) = 0.0447, chi(2) = 1.19). For x = 0.1 the XRD study indicates formation of cubic perovskites with all rare-earth cations. Electron diffraction and high resolution electron microscopy studies performed on Sr(0.9)Ln(0.1)CoO(3-delta), Ln = Y, Eu, Dy, Ho revealed the presence of crystallites with brownmillerite (a approximate to root2 x a(per), b approximate to 4 x a(per), c approximate to root2 x a(per)), tetragonal perovskite (a approximate to a(per), c approximate to 2 x a(per)) and Sr(0.7)Ln(0.3)CoO(2.62) type (a approximate to 2 x a(per), c approximate to 4 x a(per)) structures. For Ln = Sm, only XRD cubic perovskite phases were observed for all compositions, 0.1 less than or equal to x less than or equal to 0.5. In the Sr0.5Eu0.5CoO3-delta sample, crystallites of perovskite, tetragonal perovskite and Sr(0.7)Ln(0.3)CoO(2.62) type were observed in the TEM study. (C) 2004 Elsevier SAS. All rights reserved.