Melt-assisted synthesis to lanthanum hexaboride nanoparticles and cubes

Lanthanum hexaboride ( $$\hbox {LaB}₆$$ ) nanocrystals and cubes were successfully synthesized at $$700{^\circ }\hbox {C}$$ for 2 h under argon atmosphere by a melt-assisted method using $$\hbox {LaCl}₃$$ and $$\hbox {NaBH}₄$$ as reactants, NaCl–KCl or zinc or NaCl–KCl–zinc as reaction melt. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. XRD patterns and Raman spectra confirmed the formation of $$\hbox {LaB}₆$$ with high purity. TEM and SEM results showed $$\hbox {LaB}₆$$ powders prepared in mixed molten salts of NaCl–KCl were mainly composed of nanoparticles with sizes of ca. 8 nm. The morphology of $$\hbox {LaB}₆$$ presented as regular cubes (100–300 nm) when metal zinc was used as reaction melt. Photothermal conversion test indicated that nanoparticles had a better photothermal conversion performance than cubes.