Oxidation of Single Crystals of Zinc Sulphide studied by Electron Diffraction

Abstract

CRYSTALS of sphalerite were heated in air until covered by a thin film showing interference colours. These crystals were photographed in an electron diffraction camera, which will be described elsewhere. The angle between the incident beam and the crystal face was very small. The wave-length was 0.053 A. (calibrated from a powder photograph of MgO and a transmission photograph of MoS2). The distance between the crystal edge and the photographic plate was 303.5 mm. Figs. 1, 2 and 3 represent the diffraction patterns in three different cases. In Figs. 1 and 2 the oxidised face was (111), and the incident beam was perpendicular (Fig. 1) and parallel (Fig. 2) to the octahedron edge. By photographing along two different octahedron edges the same pattern was obtained. In Fig. 3 the oxidised face was (110), and the incident beam was perpendicular to the cleavage edge [001]. This direction is in fact parallel to an octahedron edge. The diffraction patterns are all of the transmission type, on which is superposed a faint powder photograph. They form a series of photographs such as would be expected if we had photographed a single crystal structure in different directions, the crystal having for each direction of the incident beam the form and dimensions necessary for obtaining a point pattern.