X-ray Study of Preferred Orientation in Pyrolytic Boron Nitride

Abstract

THE preparation of boron nitride by vapour phase deposition on a hot target has been reported by the British Ceramic Research Association1 and more recently by Belforti, Blum and Bovarnick2. In the latter publication, the deposits are described as having turbostratic layer disorder and a high degree of preferred orientation of the crystallites. In support of these claims the authors show two X-ray diffraction patterns obtained with a pyrolytic sample and a randomly oriented powder sample. The turbostratic layer disorder is evident from the two-dimensional lattice type reflexion (10) in the pyrolytic pattern and from the expansion of the unit cell height which is indicated by the shift of the (00l) reflexions to lower scattering angles. The relative intensities of the two patterns suggest the presence of some preferred orientation in pyrolytic boron nitride, but do not support the authors' contention that the basal planes of the crystallites are “essentially parallel to the deposition surface”.