Silicon

Silicon is one of the most widely used elements, it is important to plant and animal life. Silica is found in plant ashes and in the human skeleton. Silicon is an important ingredient in steel. Silicon mixed with gallium, arsenic, boron, etc. is used to produce transistors, solar cells, rectifiers, and other important solid-state electronic devices. Silicones range from liquids to hard solids and have many useful properties, including use as adhesives, sealants, and insulators. Sand and clay, which have silicon in them, are used to make building materials. Silica is used to make glass, which has many useful mechanical, electrical, optical, and thermal properties.

Silicon makes up 25.7% of the earth's crust, by weight, making it the second most abundant element (exceeded by oxygen). Silicon is found in the sun and stars. Silicon is not found free in nature. It commonly occurs as the oxide and silicates, including sand, quartz, amethyst, agate, flint, jasper, opal, and citrine. Silicate minerals include granite, hornblende, feldspar, mica, clay, and asbestos. Silicon crystallizes in a diamond cubic crystal structure.

Metallurgical grade silicon crystal is produced by carbothermic reduction of quartz in melting plants in the metallurgical industry, the tops and bottoms contain small amounts of impurities and dislocations and are therefore cut off. This cut-off and polysilicon which is not pure enough for the electronic industry goes to the solar industry, and up to about 2002, this was enough to cover the material need for the solar cell industry. After 2002, however, the demand surpassed the supply. This has lead to a silicon shortage and a price increase. In the Siemens process, silgrain (>99.6 % purity) is used. Silgrain is then reacted with hydrochloric acid in the presence of a copper catalyst. The main product obtained is trichlorosilane (SiHCl3), which is