Quartz crystal growth in hydrothermal autoclave
Hydrothermal autoclaves are widely used in quartz crystal growth. Distribution
of temperature, quartz concentration and flow structure in the upper chamber
containing crystal seeds influence the quality of grown crystal. The flow in
the autoclave appears to be unsteady and three dimensional due to the effect
of buoyancy. Iso-surface for the flow velocity equal to 5 cm/s is shown in Figure 1
to illustrate features of mass transfer in the chamber. Heat and mass transfer
occurs through the baffle opening by mixing hot and cooled solution.
The baffle subdividing the upper and lower chambers may be designed in
a way to get appropriate temperature and quartz concentration distribution
around growing crystals, Figure 2.
Fig. 1. Temperature
distribution and flow pattern in the near-baffle region.
Instantaneous temperature and quartz concentration distributions in a vertical