Precipitation in the Ilmenite-hematite System

Abstract

Although a miscibility gap in the FeTiO₃ — Fe₂O₃ system has been known from optical examination for many years (for a review see Ramdohr, 1969), the fact that the interface between precipitate and matrix is semicoherent, i.e. is composed of an array of misfit dislocations, was first reported by Christie et al. (1971). Cullen et al. (1973) have since suggested that the Burgers vectors of the misfit dislocations are of the type 1/3<112̄0> and that the dislocations are dissociated into quarter partiais, consistent with the model of Kronberg (1957) for corundum. In the present paper, we describe further aspects of precipitation in this system, and focus on the precipitate morphology and on additional analysis of the array of misfit dislocations. It is emphasized that our conclusions on the nature of the misfit dislocations differ significantly from those of Cullen et al. (1973).