Crystal growth from
Solution
High temperature
Crystal growth
Low temperature
Crystal growth
Slow cooling
Method
Solvent evaporation
Method
Temperature gradient
Method
A saturated solution above the room temperature is poured in a crystallizer and thermally
sealed.
A seed crystal is suspended in the solution and the crystallizer is kept in a water
thermostat, whose temperature is reducing according to a pre assigned plan, which results in the :
formation of large single crystals.
The need to use a range of temperature is the origin of
disadvantages
In this method, an excess of a given solute is established by utilizing the difference
between the rates of evaporation of the solvent and solute. In contrast to the cooling method, in
which the total mass of the system remains constant, in the solvent evaporation method, the
solution loses particles, which are weakly bound to other components, and therefore the volume
of the solution decreases.
The transport of material forms a hot region containing the source of the material to be
grown, to a cooler region where solution is super saturated result in the crystal growth. A smaller
variation in the temperature between the source and the crystal has larger effects on growth rate.
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The solvents are considered generally effective at temperatures above room
temperature. Also the concepts of low temperature solution growth are applicable
equally well.
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. In the growth of crystals from high-temperature solutions, the constituents
of the material to be crystallized are dissolved in a suitable solvent and crystallization
occurs as the solution becomes critically supersaturated. The most widely used high
temperature solution growth technique is the flux growth.
Hydrothermal
growth
By using this method we can make a single crystal by using aqeous solution at high temperature and pressure.
The principle of hydrothermal method is that an insoluble material at ambient temperatures could be made soluble using high temperatures and pressures.
At the hotter end the nutrient solute dissolves, while at the cooler end it is deposited on a seed crystal, growing the desired crystal.
: : 
Advantages
Materials which have a high vapour pressure near their melting points can be grown by the hydrothermal method
The method is also particularly suitable for the growth of large good-quality crystals
:
The crystal growth is performed in an apparatus consisting of a steel pressure vessel called an autoclave, in which a nutrient is supplied along with water
Disadvantage
Autoclave is expensive
Gel growth method
The principle used in this crystal growth techniques is very simple solution of two suitable compounds give rise to required crystalline substance by mere chemical reactions,
Types
Physical gel
Chemical gel
Gel which is obtained by Physical process such as cooling is called physical gel.Eg. Gelatin, clay.
Gels formed by chemical reaction such as hydrolysis (or) polymerization are called chemical gels. E.g. Silica, Polyacryalamide.
Advantages
It prevents turbulence and formation of good crystals by providing a framework of
nucleation.
The convection is absent in growth experiments.