The structure of the homologous compounds InMO3(ZnO)m (M=In, Fe, Ga, and Al, m=integer) is considered to be a layered structure, consisting of InO21− layer (In-O) ) interleaved with MZnmOm+11+ layers (M/Zn-O) along the c-axis. In the M/Zn-O layers, the distribution of two kinds of metal atoms is considered to be random fashion from X-ray diffraction analysis. However, in the previous HRTEM study of InFeO3(ZnO)m with m larger than 6, we found a modulated structure, where the image contrast showed a sinusoidal modulation curve present only in the Fe/Zn-O layers. Elemental analysis by EDS clarified that the modulated structure was caused by the ordering of Fe atoms within the Fe/Zn-O layers. In the present study, we try to observe In2O3(ZnO)m compounds, where Fe3+ atoms are replaced by In3+ atoms which have larger ionic radii. We are interested in whether the replacement of Fe3+ by In3+ atoms may cause any structural changes between In2O3(ZnO)m and InFeO3(ZnO)m.

The samples were prepared by heating powders of In2O3 and ZnO sealed in Pt tube at 1350 °C for about 3 days and then rapidly cooled down to room temperature. The electron microscope observation was performed by using JEM-2000EX, operated at an accelerating voltage of 200 kV.