PIXE and EPMA analysis of c-BN

In this paper we present an analysis of cubic boron nitride powders performed by means of PIXE (particle induced x-ray analysis) and EPMA (electron probe microanalysis). The scope of this research is to determine the impurity contents of c-BN produced by the HPHT method. With respect to the electron probe microanalysis, PIXE has a much higher elemental sensitivity due to the much lower bremsstrahlung background. A further advantage of PIXE is the large analytical depth (33 micrometer for 2.4 MeV protons). PIXE measurements were performed at the National Laboratory Legnaro (Italy) by using a 2.4 MeV proton beam at the nuclear microprobe facility. The beam was focused, within 5 micrometer spot size, on single cBN grains (average dimension around 100-200 micrometer) which were individuated by observing the strong luminescence induced by protons. The synergetic combination of PIXE and panchromatic ionoluminescence allowed us to estimate the statistical distribution, in several grains, of the impurity content in c-BN. In particular, we observed a strong contamination of silicon and calcium, which are the main contaminants of the precursors used in the cBN synthesis. PIXE and EPMA analysis of c-BN