Crystal growth - Solidification and Crystallization

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