Study of structural variation in YBaCo4O7+δ by electron diffraction

In recent years, the layered cobalt oxide, YBaCo4O7+δ, has attracted much attention due to its interesting structural, electronic and magnetic properties. The basic structure of the oxygen-stoichiometric YBaCo4O7 has been described as a mixture of hexagonal closed packing (hcp) and cubic closed packing (ccp) with oxygen atoms stacking along c axis in the sequence -A-B-C-B- [1], which consists of alternating layers of Kagome and triangular lattices of cobalt atoms [2]. The Kagome and triangular layers are made up of the corner-sharing oxygen tetrahedra with the centres occupied by Co2+/Co3+ ions in the ratio of 3/1. In this work, the structure of YBaCo4O7+δ prepared by the solid state reaction was studied by means of electron diffraction. Compared with its parent phase YBaCo4O7, a phenomenon of structural variation due to introducing of extra oxygen in the structure has been observed. Origin of structural modulation is discussed.