Polycrystal

A photo of electrical steel (coating removed) showing polycrystalline structure

Microscopically, a crystal (top) has atoms in a near-perfect periodic arrangement; a polycrystal (center) is composed of many microscopic crystals (called "crystallites" or "grains"); and an amorphous solid (bottom), such as glass, has no periodic arrangement even microscopically.

Polycrystalline materials are solids that are composed of many crystallites of varying size and orientation. The variation in direction can be random (called random texture) or directed, possibly due to growth and processing conditions. Fiber texture is an example of the latter.

Almost all common metals, and many ceramics are polycrystalline. Some elements such as sulfur, while usually occurring in polycrystalline form, may also occur as single crystals.^[1] The crystallites are often referred to as grains, however, powder grains are a different context. Powder grains can themselves be composed of smaller polycrystalline grains.^[2]

Polycrystalline is the structure of a solid material that, when cooled, forms crystallite grains at different points within it. The areas where these crystallite grains meet are known as grain boundaries.

See also

• Crystallography
• Grain boundary
• Monocrystal
• Polycrystalline silicon

References

Further reading

• Lau, J. (2009). "Implementation of Two-Dimensional Polycrystalline Grains in Object Oriented Micromagnetic Framework". Journal of Research of the National Institute of Standards and Technology (National Institute of Science and Technology) 114 (1): 57. doi:10.6028/jres.114.005.