Lanthanides: Boride, Carbide, and Nitride Compounds
Published Online: 17 DEC 2012
Copyright © 2011 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Inorganic and Bioinorganic Chemistry
How to Cite
Mori, T. 2012. Lanthanides: Boride, Carbide, and Nitride Compounds. Encyclopedia of Inorganic and Bioinorganic Chemistry. .
- Published Online: 17 DEC 2012
Rare earth elements form a rich variety of compounds with boron, carbon, and nitrogen. The rare earth borides, carbides, and nitrides tend to be highly refractory compounds, typically with melting points above 2300 K. One way of looking at the less metal-rich compounds is that the boron, carbon, and nitrogen atoms, respectively, form strongly covalent atomic networks in which rare earth atoms occupy particular spaces/voids. The strong covalent bonding among the network atoms is the origin for the high temperature stability, while the rare earth elements typically play a critical role in the physical properties, namely, functionalization of the material.
For example, especially in the case of boron, boron has one less electron than carbon and therefore it is electron deficient when forming atomic networks compared to carbon networks such as graphite and fullerenes. However, this causes boron to have an especially good affinity with the rare earth elements, which are localized and can occupy voids in the boron network while readily supplying electrons to stabilize novel structures, providing a wide variety of compounds that are introduced in this chapter, together with carbides and nitrides. Furthermore, the shell of f electrons can provide interesting physical properties such as magnetism and luminescence and also provide possible tuning of the electronic properties. In this sense, as functional materials, the rare earth elements play a critical role in the functionalization, although their content may be low in the higher borides, carbides, and nitrides. This is one important direction in which to strive in the current world where natural resources are limited, namely, to highly functionalize materials that are mainly composed of abundant light elements through the innovative use of a small amount of rare element.
In this chapter, I briefly review what is known of the rare earth borides, carbides, and nitrides. This review would particularly like to showcase interesting features of the crystal structure and intriguing physical properties ranging from the fundamental to the very applicable, with an emphasis on recent emerging results in important functionalities such as magnetism, thermoelectricity, and superconductivity.
- rare earth;
- layered compounds