Lanthanum hexaboride (LaB6) is a well known as a kind of thermionic material. Its ability to emit electrons has been widely exploited on sintered hexaboride ceramics. It has been used to build hot cathodes for a large variety of applications, including electron guns in cathode tubes, cathodes for plasma production and electron microscopes.
LaB6 – based materials, as possible candidates for solid absorbers in Concentrating Solar Power (CSP) systems. Bulk LaB6 materials were thermally consolidated by hot pressing starting from commercial powders.
In the field of material processing, LaB6 is also used as additive to other diboride ultra-high temperature ceramics (UHTCs) for improving their oxidation resistance at extreme temperatures. Recently, the attention on optical properties of LaB6 has been renewed, but to the best of our knowledge, it is mainly restricted to the use of this material in form of nanoparticles. Because of its well-defined plasma reflection edge making it a textbook case, optical properties of bulk and thin film LaB6 have been investigated and theoretically modeled in the past.
Lanthanum hexaboride can have a solar absorbance comparable to that of the most advanced solar absorber material in actual plants such as Silicon Carbide, with a higher spectral selectivity. On the other hand, LaB6 has also the appealing characteristics to be a thermionic material, so that it could act at the same time both as direct high-temperature solar absorber and as electron source, significantly reducing system complexity in future concentrating solar thermionic systems and bringing a real innovation in this field.
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