A fine-particle transmission electron microscope investigation of CrO₂ and CrO(OH)

A transmission electron microscope imaging and diffraction investigation has been performed on small CrO2 crystallites. The acieular crystal morphology has been observed and electron-diffraction evidence is presented which indicates the presence of a very thin CrO(OH) layer of 6-13 A. CrO2 has been partly converted topotactically to orthorhombic CrO(OH) in hot water and single-crystal electron-diffraction evidence is used to establish this topotactic relationship. Under sufficiently high temperatures or electron-beam irradiation, CrO2 and CrO(OH) convert topotactically to Cr2O3, as seen from single-crystal electron-diffraction data. This last conversion is further characterized using high-resolution dark-field microscopy which reveals the presence of interference patterns from the formation of microcrystalline domains. © 1980 Taylor & Francis Group, LLC.