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Chapter II Solution Growth….
super saturation and different kinetic coefficients and also on nonlinear
dependence of growth rate on super saturation V(σ). The rates of layer
generation by homogeneous and heterogeneous nucleation and due to
dislocations depend on the linear energies of the steps, which differ
significantly for various faces. Therefore, at small deviations from equilibrium
and at low growth rates, the face velocities differ widely on non-linear part of
V(σ). At large deviations from equilibrium, the acts of incorporating particles at
kinks and steps as well as transport over the surface and the bulk,
increasingly become the limiting stages of the process [37]. The growth of
crystal at approximately equivalent rate along all the directions is a
prerequisite for its accurate characterization. This will result in a large bulk
crystal from which samples of any desired orientation can be cut. Further,
such large crystal should also be devoid of dislocation and other defects.
These imperfections are isolated into defective region surrounded by large
volume of high perfection, when the crystals grow with a bulk habit. In the
crystal, which grows as needle or plates, the growth dislocation propagates
along the principle growth direction of the crystal [2]. Needle like crystals have
very limited application and plate like crystals are needed to be favorably
oriented. Change of habit in such crystals, which naturally grow as needles or
plates, can be achieved by any one of following ways
(1) Changing the temperature of growth
(2) Changing the pH of solution
(3) Adding a habit modifying agent
(4) Changing the solvent
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