Low temperature synthesis of low thermionic work function (LaxBa1−x)B6

This study presents investigations of the microstructure, morphology and emission properties of the promising thermionic material (LaxBa1−x)B6. The material was synthesised by solid-state reaction without post-synthesis purifications. Powder X-ray diffraction revealed that samples prepared at a temperature ⩾1500 °C had formed a significant proportion of solid solution (above 54 mass%). Subsequent sintering at 1950 °C caused the formation of a mixture of three solid solutions with the dominant phase being (La0.31Ba0.69)B6 ∼85% (by mass). The Richardson work function and emission constant for this boride mixture were found to be 1.03 eV and 8.44 × 10−6 A cm K−2 respectively.