Seed crystal

A seed crystal is a small piece of single crystal or polycrystal material from which a large crystal of typically the same material is to be grown in a laboratory. Used to replicate material, the use of seed crystal to promote growth avoids the otherwise slow randomness of natural crystal growth and allows manufacture on a scale suitable for industry.

Crystallization
Process-of-Crystallization-200px.png
Fundamentals
Crystal · Crystal structure · Nucleation
Concepts
Crystallization · Crystal growth
Recrystallization · Seed crystal
Protocrystalline · Single crystal
Methods and technology
Boules
Bridgman–Stockbarger method
Crystal bar process
Czochralski method
Epitaxy · Flux method
Fractional crystallization
Fractional freezing
Hydrothermal synthesis
Kyropoulos method
Laser-heated pedestal growth
Micro-pulling-down
Shaping processes in crystal growth
Skull crucible
Verneuil method
Zone melting

ProcessEdit

The large crystal can be grown by dipping the seed into a supersaturated solution, into molten material that is then cooled, or by growth on the seed face by passing vapor of the material to be grown over it.

TheoryEdit

The theory behind this effect is thought to derive from the physical intermolecular interaction that occurs between compounds in a supersaturated solution (or possibly vapor). In solution, liberated (soluble) molecules (solute) are free to move about in random flow. This random flow permits for the possibility of two or more molecular compounds to interact. This interaction can potentiate intermolecular forces between the separate molecules and form a basis for a crystal lattice. The placement of a seed crystal into solution allows the recrystallization process to expedite by eliminating the need for random molecular collision or interaction. By introducing an already pre-formed basis of the target crystal to act upon, the intermolecular interactions are formed much more easily or readily, than relying on random flow. Often, this phase transition from solute in a solution to a crystal lattice will be referred to as nucleation. Seeding is therefore said to decrease the necessary amount of time needed for nucleation to occur in a recrystallization process.

UsesEdit

One example where a seed crystal is used to grow large boules or ingots of a single crystal is the semiconductor industry where methods such as the Czochralski process or Bridgman technique are employed. Another use of seed crystals is the fact that they are the coagulant in a water-purifier packet (these packets help purify dirty water)

Also during the process of tempering chocolate, seed crystals can be used to promote the growth of favorable type V crystals[1]

See alsoEdit

ReferencesEdit