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The boron rich borides are typical of the lanthanides (and groups 1–3) whereas for the transition metals tend to form metal rich, "lower" borides. [76] The lanthanide borides are typically grouped together with the group 3 metals with which they share many similarities of reactivity, stoichiometry and structure.
Lanthanide metals react exothermically with hydrogen to form LnH 2, dihydrides. [1] With the exception of Eu and Yb, which resemble the Ba and Ca hydrides (non-conducting, transparent salt-like compounds),they form black pyrophoric, conducting compounds [6] where the metal sub-lattice is face centred cubic and the H atoms occupy tetrahedral sites. [1]
The main group metals, lanthanides and actinides form a wide variety of boron-rich borides, with metal:boron ratios up to YB 66. The properties of this group vary from one compound to the next, and include examples of compounds that are semi conductors, superconductors, diamagnetic, paramagnetic, ferromagnetic or anti-ferromagnetic. [1]
The principal use of lanthanum hexaboride is in hot cathodes, either as a single crystal or as a coating deposited by physical vapor deposition.Hexaborides, such as lanthanum hexaboride (LaB 6) and cerium hexaboride (CeB 6), have low work functions, around 2.5 eV.
The rare-earth elements (REE), also called the rare-earth metals or rare earths, and sometimes the lanthanides or lanthanoids (although scandium and yttrium, which do not belong to this series, are usually included as rare earths), [1] are a set of 17 nearly indistinguishable lustrous silvery-white soft heavy metals. Compounds containing rare ...
Erbium tetraboride is a boride of the lanthanide metal erbium. [2] It is hard and has a high melting point. Industrial applications of erbium boride include use in semiconductors, the blades of gas turbines, and the nozzles of rocket engines. [3]
Samarium is one of the few lanthanides that form a monoxide, SmO. This lustrous golden-yellow compound was obtained by reducing Sm 2 O 3 with samarium metal at high temperature (1000 °C) and pressure above 50 kbar; lowering the pressure resulted in incomplete reaction. SmO has cubic rock-salt lattice structure. [3] [23]
Silicon borides (also known as boron silicides) are lightweight ceramic compounds formed between silicon and boron. Several stoichiometric silicon boride compounds, SiB n , have been reported: silicon triboride, SiB 3 , silicon tetraboride, SiB 4 , silicon hexaboride, SiB 6 , as well as SiB n ( n = 14, 15, 40, etc.).