Modulated structure of Ag2SnO3 studied by high-resolution electron microscopy

The modulated structure of Ag2SnO3, disilver tin trioxide, was investigated by high-resolution electron microscopy and electron diffraction along four different directions. Electron diffraction showed an incommensurate one-di mensional modulated structure with a modulation wavevector of 1/6.4a*. High -resolution images showed a large number of superstructure domains with the size range 10-100 nm and orientations related by hexagonal rotation. The m odulation was determined to be displacements along the c axis of the Ag ato ms both in octahedral and linear coordination. An approximate structure mod el with a commensurate sixfold superstructure, with an orthorhombic cell (P 2(1)2(1)2(1), a = 2.922, b = 1.267, c = 0.562 nm), is proposed. Calculated images and electron diffraction patterns, based on this model, agree well w ith experimental observations.