Acta Crystallographica Section B

Structural Science

Volume 56, Part 3 (June 2000)

research papers

Acta Cryst. (2000). B56, 363-368 [ doi:10.1107/S0108768199013695 ]

Modulated structure of Ag₂SnO₃ studied by high-resolution electron microscopy

T. Oku, A. Carlsson, J.-O. Bovin, C. Svensson, L. R. Wallenberg, C. Linke and M. Jansen

Abstract: 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-dimensional 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 modulation was determined to be displacements along the c axis of the Ag atoms both in octahedral and linear coordination. An approximate structure model with a commensurate sixfold superstructure, with an orthorhombic cell (P2₁2₁2₁, a = 2.922, b = 1.267, c = 0.562 nm), is proposed. Calculated images and electron diffraction patterns, based on this model, agree well with experimental observations.

Keywords: Modulated; Electron microscopy; Electron diffraction; Silver; Tin; Incommensurate.