Crystal growth
Solidification and Crystallization
In
order to understand the crystalline state and its difference from the amorphous
state, it is important to consider the process of Solidification.
Solidification
is the transformation of material from liquid to the solid state on cooling.
When
the liquid solidifies, the energy of each atom is reduced. This energy is given
out as latent heat during the solidification process, which for a pure mental
occurs at a fixed temperature Ts as shown figure
During
solidification, the disordered structure of the liquid(constituents of material
in liquid state have more velocity, more collisions and hence have random
position) transforms to the orderly arrangement depending upon the time of
solidification. Crystal growth techniques.
The
crystal growth technique is classified into six categories namely
i.
Melt growth
ii.
Low temperature solution growth
iii.
High temperature solution growth
iv.
Hydrothermal growth
v.
Gel growth
vi.
Epitaxial growth
Melt growth:
Melt
growth is the process of crystallization by fusion and re solidification of the
starting materials
The
growth from melt is further sub-grouped into various techniques. The mani
techniques are
a)
Czochralski technique
b)
Bridgmen Technique
c)
Verneuil method
d)
Zone melting technique
The
major practical factors is to be considered during growth crystals from melt
are
1)
Velatiltiy
2)
Chemical resistivity
3)
Melting point
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