RARE EARTH KNOWLEDGE

What is rare earth?

Rare Earth elements in the periodic table lanthanide - lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and 15 with lanthanide elements is closely related to the two elements - scandium (Sc) and yttrium (Y), a total of 17 elements, known as Rare Earth elements (Rare Earth). Rare earth (RE or R).
The rare earth elements were first discovered in relatively rare minerals from Sweden, and "earth" was used as a material that was not soluble in water, so called rare earth.

Based on the electronic structure of the rare earth elements and the chemical and physical properties, and they in the mineral of the communist party of China and different ionic radius can produce different characteristics, 17 kinds of rare earth elements are usually divided into two groups.

Light rare earth (also known as cerium group) includes: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium.

The heavy rare earth (also known as yttrium group) includes: terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium.

The cerium group or yttrium group is named for the dominance of cerium or yttrium in the rare earth mixture obtained from minerals.

The main physical and chemical properties of rare earth elements
Rare earth elements are typical metallic elements. Their metal activity is second only to alkali and alkaline earth metals, and is more active than other metal elements. Among the 17 rare earth elements, the active sequence of metals is arranged by scandium, yttrium, and lanthanum, which decreases from lanthanum to lutetium, which is the most active of lanthanum. Rare earth elements can form chemical stable oxide, halide, sulfide. Rare earth elements can react with nitrogen, h ydrogen, carbon and phosphorus, which are soluble in hydrochloric acid, sulfuric acid and nitric acid.
Rare earth and oxygen, sulfur, lead and other elements combine to form a high melting compound, so adding rare earth in the steel water can be used to purify the steel. Because of rare earth elements of the metal atomic radius is larger than the atomic radius of iron, it is easy to fill in the grain size and defects, and generates membrane can prevent grain continue to grow, so that the grain refinement and improve the performance of steel.

Rare earth elements have an unfilled 4f shell structure, resulting in a variety of electronic energy levels. As a result, rare earth can be used as a fine fluorescence, laser and electric light source material as well as colored glass, ceramic glaze.
Rare earth ions combine with hydroxyl, azo or sulfonic acid groups, so that rare earth is widely used in printing and dyeing industry. Some rare earth elements have characteristics of neutron capture, such as samarium, europium, gadolinium, dysprosium and erbium, which can be used as control materials and moderators for atomic energy reactors. The neutron capture area of cerium and yttrium is small, which can be used as the diluent of reactor fuel.

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