Vibrational Spectra Studies on Hexagonal BN Crystal and the Synthesis of Cubic BN

X-ray diffraction analysis is used as a reference, the infrared absorption and Raman scattering spectra of various hBN, whose real structures vary from high three-dimensional order to turbostratic structure, are measured. The results indicate that with the lowering of the crystallinity, the position of its low frequency absorption that with the lowering of the crystallinity, the position of its low frequency absorption band and FWHM of Raman spectrum lines in fundamental vibrational spectra change characteristically, and exhibit distinctive minimum peaks respective. cBN synthesis tests are carried out with these hBN as starting materials. The results show that a certain crystallinity of hBN is necessary to the formation of cBN at high pressure and temperature in the presence of metal catalyst. The dependence of cBN synthesis results upon the hBN crystallinity, which is not a simple monotonic relation. The experimental results mentioned above are analyzed and discussed.