Polycrystalline or
multicrystalline materials, or
polycrystals are solids that are composed of many
crystallites of varying size and orientation. Crystallites are also referred to as
grains. They are small or even microscopic
crystals and form during the cooling of many materials. Their orientation can be random with no preferred direction, called random texture, or directed, possibly due to growth and processing conditions. Fiber texture is an example of the latter. The areas where crystallite grains meet are known as
grain boundaries.