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Chapter: Physics - Crystal Physics

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Low temperature solution growth : Slow cooling and Slow evaporation method

The low temperature solution growth is suitable for materials which decompose at high temperature and undergo phase transformation below the melting point.

SOLUTION GROWTH

Low temperature solution growth

The low temperature solution growth is suitable for materials which decompose at high temperature and undergo phase transformation below the melting point.

 

There are two methods of low temperature solution growth. They are

i.                   Slow cooling method

ii.                 Slow evaporation method

 

SLOW COOLING METHOD

Slow cooling is the easiest method to grow bulk single crystals from solution. This technique needs only a vessel only a vessel for the solution, in which the crystals grow.

The temperature at which crystallization begin is in the range of 45oC to 75oC and the lower limit of the cooling is the room temperature.


 

SLOW EVAPORATION METHOD

In this method, the saturated solution is kept at a particular temperature and provision is made for evaporation. The basic apparatus (Manson Jar crystallizer) used for the solution growth technique is shown in the figure

Typical growth conditions involve temperature stabilization at about 0.05oC and rate of evaporation of a few mm3/h.

 

ADVANTAGES

i.                   This is a simple and convenient method of growing single crystals of large size.

ii.                 Growth of strain and dislocation free crystals.

iii.              Permits the growth of prismatic crystals by varying the growth conditions.

iv.              Only method which can be used for substances that undergo decomposition before melting.

 

DISADVANTAGES

i.                   The growth substance should not react with the solvent

ii.                 This method is application from substances fairly soluble in solvent

iii.              Small crystals are also formed on the walls of the vessel near the surface of the liquid. These tiny crystals fall in the solution and hinder the growth of the crystal

iv.              A variable rate of evaporation may affect the quality of the crystal


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