Powder sublimation and porosity evolution in sublimation crystal growth

In this paper, a numerical model that combines powder sublimation kinetics and porosity evolution phenomenon is presented. A driving force due to temperature difference is introduced into the aluminum nitride (A1N) powder sublimation kinetics. A new method to increase crystal growth rate by changing the powder geometry is proposed. The new method includes changing the initial powder porosity and creating a hole in the packed powder. Powder porosity evolution and growth rate variation are presented. Simulation results for the case with a central hole and without the hole are compared. The effect of the hole size is investigated. The results show that the powder sublimation rate increases with a hole, and it is also validated by experiments, Finally, the powder geometry is optimized using numerical simulations.