What is rare earth?
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According to the electronic layer structure and physicochemical properties of rare earth elements, and their symbiosis in minerals and different ionic radii can produce different properties, seventeen rare earth elements are usually divided into two groups.
Light rare earths (also known as 铈 group) include: 镧 , 铈, 镨 , é’• , é’·, é’ , é“• , é’† .
Heavy rare earths (also known as é’‡ group) include: 铽 , é• , é’¬ , é“’ , é“¥ , 镱 , é•¥ , é’ª , é’‡.
The sputum group or the sputum group is named because the rare earth mixture obtained by separation of minerals is often named after strontium or barium.
The main physical and chemical properties of rare earth elements:
Rare earth elements typical metal elements. Their metal activity is second only to alkali metal and alkaline earth metal elements, and is more active than other metal elements. Among the 17 rare earth elements, arranged in a lively order of metals, increasing from 钪, 钇, 镧, and decreasing from 镧 to 镥, the 镧 element is the most active. Rare earth elements form chemically stable oxides, halides, and sulfides. Rare earth elements can react with nitrogen, hydrogen, carbon and phosphorus , and are easily soluble in hydrochloric acid, sulfuric acid and nitric acid.
Easy and rare earth oxygen, sulfur, lead and other elements combine to form high melting point compounds, and therefore addition of rare earths in the molten steel, can play a purifying steel. Since the metal atomic radius of the rare earth element is larger than the atomic radius of iron , it is easy to fill in the crystal grains and defects, and a film which can hinder the growth of the crystal grains is formed, thereby refining the crystal grains and improving the properties of the steel.
The rare earth element has an unfilled 4f electron layer structure and thus produces a wide variety of electronic energy levels. Therefore, rare earth can be used as an excellent fluorescent, laser and electric light source material as well as colored glass and ceramic glaze.
The rare earth ions form a combination with a hydroxyl group, an azo group or a sulfonic acid group, so that the rare earth is widely used in the printing and dyeing industry. Some rare earth elements have the characteristics of large neutron capture cross-sectional areas, such as ruthenium, osmium, iridium, osmium and iridium, which can be used as control materials and moderators for atomic energy reactors. The neutron capture cross-sectional area of ​​sputum and sputum is small, which can be used as a diluent for reactor fuel.
Rare earths have the properties of trace elements, which can promote the seed germination of crops, promote root growth and promote photosynthesis of plants.