Chloride influence on the formation of lanthanum hexaboride: An in-situ diffraction study

LaB6 has been a material of interest for decades due to its thermionic emission, plasmonic properties, and low work function, and researchers continue to discover new properties even now. In order to meet growing interest in customizing these properties, it is important to gain better control over the system and a better understanding of the fundamental mechanism of LaB6 crystal growth and formation. Traditional synthetic methods require very high temperatures, at which point crystallization happens too quickly to be readily studied. Our discovery that LaB6 may be made using lower temperatures has made it possible to slow down crystal formation enough for lattice growth to be observed. We report here an in situ diffraction study of the reaction between LaCl3 and NaBH4. In observing the evolution of the (1 1 1), (1 1 0), and (2 0 0) lattice planes of LaB6, we have discovered that the Cl of LaCl3 has a strong influence on crystal formation, and that excess Cl, temperature and heating rate may all be used as tools to control the LaB6 final product.