The main difference between single crystals and polycrystals is their microstructure and physical properties. The following is a detailed introduction:
1. The microstructure is different. Single crystals are composed of single crystal grains, which are regularly and periodically arranged in three-dimensional space, have definite geometric shapes and fixed melting points, and exhibit anisotropy; polycrystals are composed of many small crystal grains (grains) , these grains are arranged in the same way, but their orientations are inconsistent. The grains constituting the polycrystal are randomly arranged as a whole and have no definite geometric shape, but they are isotropic in physical properties.
2. Different application fields. Because of its regular geometric shape and anisotropic characteristics, single crystals are often used in materials and equipment that require high precision and specific optical properties, such as semiconductor technology, medical imaging equipment, etc. Polycrystals are often used because of their isotropic physical properties. It is suitable for fields that do not have high requirements on the microstructure of materials, such as some metals and rock materials.