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FEM simulations and experimental studies of the temperature field in a large diamond crystal growth cell * Li Zhan-Chang(oÔ‚) a) , Jia Xiao-Peng(_¡+) a) , Huang Guo-Feng('I¹) b) , Hu Mei-Hua( {u) a) , Li Yong(o ]) a) , Yan Bing-Min(ôZ¯) a) , and Ma Hong-An(êùS) a) † a)

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A hybrid-anvil used in cubic high pressure apparatus is presented, which makes it possible to pressurize samples of 36 mm(3) volume up to 5.5 GPa and to heat simultaneously up to 1350-1400 degrees C for routine operation. The hybrid-anvil has been designed based on the theory of multilayered pressure vessels and massive support, which can save weight about 60.00% compared to the traditional anvil. We note from 10 000 times of experiments that the rate of failure crack decreases about 16.67% and the cost of anvil saves about 66.40% after the modification of the anvil. This represents a relatively simple and inexpensive anvil for material synthesis and research.

The temperature distribution in the cell of single crystal diamond grown by the temperature gradient method has been studied, which is based on the finite element method. Our results shwo that the temperature distribution in the synthetic process of single crystal diamond is not uniform. The highest temperature in the cell is located at the outside of single carbon solvent, and the lowest temperature in the cell is located near the diamond seed. The heat transfer and the mass transport have a same direction （from outside of carbon source to diamond seed）. The temperature gradient in the axial direction is higher than that in the radial direction, which explains why the size of synthetic single crystal diamond in the axial direction is larger than that in the radial direction. The model will be useful for the design of single crystal diamond grown by the temperature gradient method. Furthermore, this work will be hopeful to improve the cubic anvil type high pressure techniques for the synthesis of high quality diamond crystals.