Study of Thin Films of Cobalt Oxide

Abstract

So far very little attention has been given to thin oxide films on cobalt¹. This report deals with the structural features observed by transmission electron microscopy of chemically stripped films (from hundreds to a few thousands Å thick) formed on cobalt. The material used was spectrographically pure polycrystalline cobalt supplied by Johnson Matthey and Co., Ltd, in the form of rolled strips (0.05 cm thick). X-ray diffraction of the metal as received revealed the structure as hexagonal close packed (h.c.p.). Studies of the oxidation² as well as the dilatometric curve of the metal indicated a change in the crystal structure about 386° C, which is presumably due to the allotropic transformation of cobalt from h.c.p. to face-centred cubic (f.c.c.) form.