A high-resolution electron microscopy examination of domain boundaries in crystals of synthetic goethite

Abstract

High-resolution electron microscopy and electron diffraction have been used to elucidate the structure of domain boundaries in crystals of synthetic goethite (α-FeOOH). Composite crystals of acicular α-FeOOH often show single-crystal electron-diffraction patterns and the intergrowths have been observed to be highly coherent across the domain boundaries. Twin crystals have been examined and show diffraction patterns and high-resolution images which correspond to composite crystals mutually rotated by 120° about the [100] axis. These results are discussed in relation to postulated mechanisms of crystal growth and to the dissolution behaviour of goethite in acid solution.