XRD Evaluation of Relative Mechanical Strength and Irradiation Resistance of Synthetic Diamond

We continue here our previous work where SD powders were significantly strengthened by irradiation with electrons of lower energy under smaller dose. Previous results were obtained from the crushing strength analysis, no XRD was applied. In present work, powders of synthetic diamond with low strengthwere sorted on sets with different grain size. As established, the sets had various crushing strengths and morphology. They were irradiated with high energy electrons (6.5 MeV, D = 2 × 1019 and D = 6 × 1019 cm?2, Tirr = 450 K) and analyzed using XRD (CuKα) before and after irradiation. Nonlinear dependences a(Θ) = f{R(Θ), where a(Θ) is lattice constant and R(Θ) is Raily function, and the discovered extra-splits (additional to α1-α2-doublets on CuKα) of basic peaks in XRD patterns from the SD sets, testified that crystal lattice of diamond in sets was variously distorted, like of cBN doped with rare earth elements. As established, the first irradiation led to decreasing distortions, the more significantly the higher initial strength of the set. The second irradiation produced softening and increasing distortions of crystal lattice of diamond, the more effectively the less initial strength of diamond. XRD allows indirectly to presort synthetic diamond off the material with critically low relative mechanical strength as well as evaluate resistance of diamond crystal lattice against heavy irradiation and other external impacts.

XRD Doping Control of Light-Emitting cBN with a Large Size Mismatch between the Dopant and Intrinsic Atoms

Cubic boron nitride (cBN) as the outstanding representative of the family of semiconducting wide bandgap nitrides and the closest analogue of diamond, is produced and investigated. XRD as method for doping control of cBN with impurities of large atomic sizes, is suggested. The larger an atomic size mismatch between doping and intrinsic atoms of a semiconductor’s crystal lattice, the stronger its response through own strains and distortions. The distortions are expected to be notable in the case of the smallest intrinsic atoms of cBN and diamond. The light-emitting cBN doped with various rare-earth elements (RE) in different concentrations under high pressure conditions is synthesized in form of the cBN: RE single phase micropowders. The micro-powders showed the discrete photoluminescence spectra in IR-, red and green spectral ranges which were attributed to the intra-electronic transitions of RE3+ ions located in cBN crystal lattice. The locations of the RE3+ ions in cBN crystal lattice are discussed. The data of XRD (CuKα) analysis of the cBN:RE micropowders are repre- sented. Extra-splits (as the additional ones to the α1-α2-splits on CuKα) of the cBN parent peaks in XRD patterns of the cBN: RE, are discovered and analyzed using appropriate computer programs. As established, crystal lattice of cBN due to the incorporation of RE3+ ions, represents a disordered solid solutions which are nonuniformly distorted in dependence on the ions’ size and their concentrations in cBN. Results of the present work can be useful to manufacture cBN with predictable functional properties, as well as for in situ doping control of cBN and diamond.