دانلود کتاب نانومواد سرامیکی مبتنی بر خاک کمیاب پیشرفته

Rare earth elements include a group of 17 elements from the periodic table, namely 15 lanthanides with scandium (Sc) and yttrium (Y) (Castor, 2006). Scandium and yttrium are also considered rare earth elements because they are often found in the same mineral deposits as lanthanides and also have similar chemical properties to lanthanides (Balaram, 2019). All rare earth elements have been reported to be found in nature but not in the form of pure metal. Among them, although Promethium has been reported as the rarest element, it is found only in very small amounts in natural materials because it has no stable isotopes (Castor, 2006). Studies have indicated that in the group of lanthanides, the configuration of the valence electrons corresponding to the outermost shell is the same for all elements, so that the 4f orbitals are filled with enhancing atomic number. Screening of 4f orbitals can cause very similar chemical and physical attributes of these elements. The phenomenon of “lanthanide contraction” is also reported as another related consequence in which the ionic radius of the members belonging to the group reduces from La31 (1.06 A ° ) to Lu31 (0.85 A ° ) (Balaram, 2019).