It is a refractory ceramic material that has a melting point of 2210 °C, and is insoluble in water and hydrochloric acid.

[2] It has a low work function and one of the highest electron emissivities known, and is stable in vacuum.

Lanthanum hexaboride slowly evaporates from the heated cathodes and forms deposits on the Wehnelt cylinders and apertures.

LaB6 is also used as an X-ray powder diffraction (XRD or pXRD) peak position and line shape reference standard.

[6] It is therefore used to calibrate measured diffractometer angles and to determine instrumental broadening of diffraction peaks.