Enhancing the thermionic electron emission performance of hafnium with nanocluster doping

Abstract

Scandate cathode as a thermionic electron emission material has attracted broad interest owing to its high electron emission capability. Despite the large number of studies on the electron emission of the scandate tungsten cathode, there is a lack of understanding of the performance of scandium oxide incorporated in other refractory metal matrix. In this work, by applying first-principles calculations, we study the role that Sc2O3 nanocluster plays in enhancing the electron emission of the Hf cathode (labeled as Sc2O3@Hf). We find that Sc2O3@Hf is both thermally and mechanically stable, exhibits complex surface structures, and possesses inverse relationship between surface energy and work function. Moreover, the work function of the Hf (0001) surface can be reduced to 3.50 eV due to the change in the vacuum level when Sc2O3 nanocluster is doped, while the work function of the Hf (101¯2) surface can be reduced to 3.39, 3.39, and 3.03 eV when doped with Sc2O3, Y2O3, and CeO2 clusters, respectively.