Ordering effects in the crystal structure and electrochemical properties of the Gd0.5Ba0.5Mn0.5Fe0.5O3−δ perovskite

Abstract

Layered-type ordering and oxygen vacancies ordering are revealed in GdBaMnFeO_6−δ perovskite. Selected area electron diffraction and high-resolution transmission electron microscopy results indicate a modulation of the crystal structure. Ba and Gd ordering in (001)_p layers is confirmed by high angle annular dark field scanning transmission electron microscopy and electron energy-loss spectroscopy. These techniques also revealed formation of layer-stacking defects in the crystals. Direct imaging of the oxygen sublattice is obtained by phase image reconstruction. Location of the oxygen vacancies in the (GdO)_x layers is achieved by analysis of the intensity of the averaged phase image. Physical properties of the GdBaMnFeO_6−δ perovskite, are likely to be strongly affected by its ordering effects and crystal microstructure. In this sense, layered-type GdBaMnFeO_6−δ perovskite show better electrochemical properties as cathodes in SOFCs than ion disordered Gd_0.5Ba_0.5Mn_0.5Fe_0.5O_3−δ perovskite.