Research of phase transition of pyrophyllite after high temperature and high pressure

The pyrophyllite assembly used in synthesis of diamond crystal was analyzed by X-ray diffraction and Raman spectrum examination. The results indicated that the pyrophyllite crystals were gradually decomposed into hard diaspore, quartz and kyanite under high temperature and high pressure. It is concluded that a suitable thickness of dolomite drive pipe wall would prevent the formation of excessively high hardness kyanite, which make more even distribution of pressure and temperature in the high pressure assembly. The results are very important to the synthesis of high quality diamonds.