Distribution Of Shear Stress On The Surface Of KDP Crystal Grown From Solution

The KDP crystal was developed from the 40's of the twentieth century; it is one kind of electro optics and non-linear optical materials. It is broadly applied to some high technology fields such as laser frequency conversion, electro optics modulated, ray celerity switch and so on. It is characterized by very big electro optics and non-linear optical coefficient and high damage threshold. In particularly large size single crystal for the ray to get across can be grown. Large size KDP crystal is the only material which can be used in ICF(inertial confinement fusion)up till now. Recently the hotspots of investigation about KDP crystal are: improving its growth speed, shortening its growth cycle and reducing its cost under the condition of maintaining a good crystal quality.The morphological stability and inclusion formation depend strongly on the shear stress distribution at the crystal surface; the direction, velocity and height of growing step at the crystal surface are consanguineously related with the state of solution's flowing near the crystal surface, the shear stress distribution at the crystal surface has important effect on the thickness of boundary layer, the thickness of boundary layer has great influence on the quality and the growing velocity of KDP crystal. So study on the shear stress distribution at the crystal surface is propitious to grow large and high quality KDP crystal.A three dimensional numerical simulation of the shear stress distribution on KDP crystal's surface has been carried out by using the finite volume method. The effect of the surface shear stress distribution on the growth of KDP crystal has been obtained, which is helpful for the experiment study on the mechanism by AFM in the future. The effects of the magnitude of the solution velocity,the position of solution inlet and seed crystal size on the surface shear stress distribution of KDP crystal is considered. By analyzing the velocity vector distribution of vertical, horizontal and side section in the crystallizer and the shear stress distribution at the KDP crystal surface such as up-surface, behind-surface, left-surface, the following results can be found: the value of the shear stress at the side of crystal nearby the inlet is larger and it will increase with the increase of the inlet velocity and the seed size. The shear stress distributions at KDP crystal surface will change with the change of the inlet velocity, the position of the inlet and the seed size. The conclusions of modified physical model are similar to the previous conclusions. A little difference appears here, when the calculated conditions change, the shear stress distribution at the KDP crystal surface change not so much compared with the previous results.