AN EELS AND XAS STUDY OF CUBIC BORON-NITRIDE SYNTHESIZED UNDER HIGH-PRESSURE - HIGH-TEMPERATURE CONDITIONS

Cubic Boron Nitride (c-BN) single-crystals have been synthesized under high pressure and high temperature conditions (HP - HT) using hexagon al Boron Nitride (h-BN) precursors. We have performed a study of both phases with electron (EELS) and X-ray (XAS) spectroscopy that are comp ared. The c-BN ELNES spectra at B-K and N-K edges are found to be cons istent with the XANES (XAS) data, although the energy resolution achie ved with X-rays is better than that obtained by EELS with a LaB6 filam ent. However, XAS is at a disadvantage by comparison with EELS owing t o the presence of the N-K edge second order. Attempts were made to dop e c-BN with carbon atoms. The examination of the EELS spectra reveals that the incorporation of carbon species in the BN material is always accompanied by the addition of oxygen. Several samples were analyzed b oth with selected area electron diffraction and energy loss spectrosco py. Most probed crystals containing C (and therefore O) were found to be hexagonal. These results emphasized that the range of existence of the cubic phase is very narrow around the binary composition.