Polycrystalline vs Monocrystalline
Crystalline is being a crystal, composed of crystal or resemble a crystal. Crystalline solids or crystals have ordered structures and symmetry. The atoms, molecules, or ions in crystals are arranged in a particular manner, thus have a long-range order. In crystalline solids, there is a regular, repeating pattern; thus, we can identify a repeating unit. By definition, “a crystal is a homogenous chemical compound with a regular and periodic arrangement of atoms. Examples are halite, salt (NaCl), and quartz (SiO2). However, crystals are not restricted to minerals: they comprise most solid matter such as sugar, cellulose, metals, bones and even DNA.” Crystals are naturally occurring on earth as large crystalline rocks, such as quartz, granite. Crystals are formed by living organisms too. For example, calcite is produced by mollusks. There are water-based crystals in the form of snow, ice, or glaciers. Crystals can be categorized according to their physical and chemical properties. They are covalent crystals (e.g. diamond), metallic crystals (e.g. pyrite), ionic crystals (e.g. sodium chloride), and molecular crystals (e.g. sugar). Crystals can have different shapes and colors. Crystals have an aesthetic value, and it is believed to have healing properties; thus, people use them to make jewelry.
In nature, most of the time, crystals appear to have disrupted their long-range order. Polycrystalline are solids that are composed of many numbers of small crystals. These are arranged in different orientations and are bound by highly defective boundaries. The crystals in a polycrystalline solid are microscopic, and they are known as crystallites. These are also known as grains. There are solids, which are composed of a single crystal like gems and silicon single crystals, but these occur very rarely in nature. Most of the time solids are polycrystalline. In a structure like this, number of single crystals is held together by a layer of amorphous solids. Amorphous solid is a solid, which lacks a crystalline structure. That is, it does not have long-range, ordered arrangement of atoms, molecules, or ions within the structure. Therefore, in a polycrystalline structure, the long-range order has been disrupted. For example, all the metals and ceramics are polycrystalline. In these, the order and the orientation are very random. It can be determined from the way the polycrystalline solid has grown or by the processing conditions.
The word “mono” means one. So the word monocrystalline means a single crystal. Monocrystalline solids are composed of a single crystal lattice and, therefore, it has a long-range order. So there are no grain boundaries. This uniformity gives them unique mechanical, optical, and electrical properties. Single silicon crystals are used in semiconductors. Since monocrystalline solids have a higher electrical conductivity, they are used in high performing electrical applications. Further, their strength is very high, so used for producing high strength material.
What is the difference between Monocrystalline and Polycrystalline?
• Polycrystalline solids are composed of many numbers of crystalline solids, whereas monocrystalline has a single lattice.
• Monocrystalline solids have ordered structures and symmetry but, in a polycrystalline structure, the long-range order has been disrupted.
• Monocrystalline structure is uniform and has no boundaries, but polycrystalline structure differs from this. It does not have a continuous structure, and it has boundaries between grains.