The features of determination of residual stress in the diamond by Raman spectroscopy of carbon substance inclusions

Raman spectroscopy was used to study the inclusions of carbon substance in placer diamonds from the rivers B. Shchugor and B. Kolchim, (Perm Region, Krasnovishersky district, Russia). It is established that inclusions of carbon substance within natural diamonds could be presented by either graphite of different degree of crystallinity, or low ordered glass-like carbon. The correlation between a Raman shift of T2g diamond band (1332 сm-1 at room conditions) from G and G+D` graphitic carbon bands in Raman spectra has been analyzed. The dependence of residual deformation of a diamond lattice of crystallinity degree of carbon inclusions was defined, the latter was marked with appearance of a D`-bands in Raman spectra. It was shown that correct estimation of the residual tension of carbon substance inclusions within diamond could be made only on the basis of Raman data of high ordered graphite (FWHMG = 12-20 сm-1), or by nanocrystalline graphite (FWHMG = 20-40 сm-1) having a D` band within a spectrum. It is not correct to use the inclusions of low ordered carbons (FWHMG = 40-70 сm-1) for the residual tension with the standard graphite coefficient for calculations, at the case the residual pressure can be estimated only by residual deformation of a diamond matrix. Without the complex analysis of the carbon inclusions Raman features and initial wrong acceptance of nanocrystalline and glass-like carbons as high ordered graphite the residual pressure is overestimated up to 1.5-2 times.