A high-frequency (94GHz) low-temperature electron paramagnetic resonance study was made of brown-to-dark colored crystals which had been selected from crystalline powders that had been prepared by using the high-pressure high-temperature technique and excess B. It was recalled that previous investigations of dark polycrystalline powders, using low-frequency (9.4GHz) electron paramagnetic resonance spectroscopy, had identified 2 paramagnetic species which were associated with the brown-to-dark coloration. The spectrum of one of them was observed only above 100K. The other species consisted mainly of anisotropic paramagnetic centers with an electron spin of S = ½ and a local symmetry axis along one of the crystal <111> axes.

Point Defects in Cubic Boron Nitride Crystals. S.V.Nistor, M.Stefan, E.Goovaerts, A.Bouwen, D.Schoemaker, G.Dinca: Diamond and Related Materials, 2001, 10[3-7], 1408-11