LAUSR

Abstract Samarium borides exhibit unique electrical and magnetic properties that have potential applications in a number of fields. However, it is still challenging to obtain crystalline samarium borides with controllable stoichiometry and morphology by simple synthetic methods. Herein, we report the one-pot synthesis of two samarium boride phases via the reactions between samarium halides and NaBH4 in molten LiCl-KCl. The stoichiometry and morphology were controlled by varying the precursor ratio and reaction time. The crystalline SmB4 possesses rod-shaped structure with diameters around 60–90 nm, and nanocubes around 50–100 nm were obtained for SmB6. On the basis of XRD and SEM results, the SmB4 nanorods obtained at a Sm/B ratio of 1:3 evolve from the initially formed SmB4 nanofilms, while formation of the SmB6 nanocubes at a Sm/B ratio of 1:10 is mediated by SmB4. The transition from film-shaped SmB4 to cubic SmB6 most likely results from the destruction of the SmB4 nanocrystal upon partial reduction of Sm3+ to Sm2+ in the presence of excess NaBH4, which is consistent with the change in oxidation state of samarium from XANES analysis. The SmB4 nanorods and SmB6 nanocubes synthesized in molten salt possess similar paramagnetic properties to those obtained by other methods, which demonstrates the capability for the facile synthesis of lanthanide borides with controllable stoichiometry and morphology in molten salt under mild conditions.