Rare earth, also known as rare earth element, is a general term for 17 kinds of metal elements in the chemical periodic table, such as lanthanides and lanthanum and cerium. It is an important non-renewable strategic material. With unique magnetic, optical, electrical and chemical properties, it can be combined with other elements into a variety of new materials. There are 250 rare earth minerals in nature, and the first to discover rare earths is the Finnish chemist John Gadolin. In 1794, the first rare earth "element" (aluminum, Y2O3) was separated from a bituminous ore-like ore. Because rare earth minerals were found in the 18th century, only a small amount of water-insoluble water could be produced by chemical methods. Oxide, historically used to call this oxide "earth", hence the name rare earth. Rare earth elements are now widely used in the automotive, electronics, aerospace, robotics, telecommunications and healthcare industries, petrochemicals, metallurgy, machinery, and other fields. Two of these rare earths, tantalum and niobium, are key raw materials for super-strong permanent magnets and are critical to the electronics, technology and automotive industries. In general, different rare earths have many important uses in different fields: 1. Military rare earth is known as “industrial gold”. Its most remarkable function is to greatly improve the quality and performance of other products. For example, it can greatly improve the steel, aluminum alloy and magnesium alloy used to manufacture tanks, aircraft and missiles. The tactical performance of titanium alloys; rare earths are also high-tech "lubricants" such as electronics, laser, nuclear industry, and superconducting. 2. The metallurgical industry adds rare earth metals or fluorides and silicides to steel, which can play the role of refining, desulfurization, neutralization and low melting point harmful impurities, and can improve the processing properties of steel; rare earth ductile iron, especially suitable for production with special The required complex iron parts are widely used in machinery manufacturing such as automobiles, tractors and diesel engines; rare earth metals are added to non-ferrous alloys such as magnesium, aluminum, copper, zinc and nickel to improve the mechanical properties of the alloy at room temperature and high temperature. 3. Molecular sieve catalysts made of rare earths for petrochemical industry have the advantages of high activity, good selectivity and strong resistance to heavy metal poisoning. They are widely used in the catalytic cracking process of petroleum; in the process of synthesizing NH3, a small amount of rare earth nitrate is used as a help. The catalyst has a treatment gas volume 1.5 times larger than that of the nickel aluminum catalyst; the composite rare earth oxide can also be used as a catalyst for exhaust gas purification of an internal combustion engine. 4, glass ceramic rare earth oxide can be used as polishing powder widely used in the polishing of optical glass, ophthalmic lens, picture tube, plastic and metal tableware; in the process of melting glass, the use of cerium oxide has a strong oxidation effect on iron, It can reduce the iron content in the glass; adding rare earth oxide can produce optical glass and special glass for different purposes; adding rare earth in ceramic glaze and enamel can reduce the fragmentation of glaze and make the product exhibit different color and luster.  5. New materials rare earth cobalt and NdFeB permanent magnet materials are widely used in the electronics and aerospace industries; garnet-type ferrite single crystals and polycrystals formed by the combination of pure rare earth oxides and ferric oxide can be used Microwave and electronics industry; yttrium aluminum garnet and bismuth glass made of high purity cerium oxide can be used as solid laser materials; rare earth hexaboride can be used to make electron emission cathode materials.