The main physicochemical properties of rare earth elements

Rare earth elements are typical metallic elements. Their metallic activity is second only to that of alkali metals and alkaline earth metals, but more active than other metal elements. In 17 rare earth elements, according to the active order of the metal, scandium, yttrium, lanthanum increase, from lanthanum to lutetium decrease, namely lanthanum is the most active. Rare earth elements can form chemically stable oxides, halides and sulfides. Rare earth elements can react with nitrogen, hydrogen, carbon, phosphorus, soluble in hydrochloric acid, sulfuric acid and nitric acid.

Rare earth is easy to combine with oxygen, sulfur, lead and other elements to form compounds with high melting point. Because rare-earth elements have a larger atomic radius of the metal than iron, they can be easily filled in the grain and defect, and generate a film that can hinder the grain growth, thereby refining the grain and improving the performance of the steel.

Rare earth elements have an unfilled 4f electron shell structure, which produces a variety of electron energy levels. Therefore, rare earth can be used as excellent fluorescent, laser and electric light source materials, as well as colored glass and ceramic glazes.

Rare earth ions and hydroxyl, azo or sulfonic acid group to form a combination, so that rare earth is widely used in the printing and dyeing industry. Some rare earth elements, such as samarium, europium, gadolinium, dysprosium and erbium, have the characteristics of large neutron capture cross-sections and can be used as control materials and speed reducers in nuclear reactors. However, cerium and yttrium with small neutron capture cross section area can be used as diluent for reactor fuel.

Rare earth has the property of similar trace elements, which can promote the seed germination of crops, the growth of root system and the photosynthesis of plants.

Some physical properties of rare earth metals