Grain-size controlled bulk cathode material was prepared by using the spark plasma sintering method in an oxygen-free system. Starting precursor nanopowders with average grain size of 50nm were prepared by high-energy ball milling. The nanopowder was fully densified at 1300C, which was about 350C lower than the sintering temperature of the coarse powders. The thermionic emission current density was measured to be 42.0A/cm2, which was much higher than the 24.2A/cm2 of coarse powders. The Vickers hardness was 1860kg/mm2, which was also higher than the 1700kg/mm2 of coarse samples. These results indicated that refining the powder grain size to nano level was beneficial in reducing the sintering temperature and promoting the thermionic emission and mechanical properties.

Preparation and Characterization of Grain Size Controlled LaB6 Polycrystalline Cathode Material. Bao, L.H., Zhang, J.X., Zhou, S.L., Wei, Y.F.: Chinese Physics Letters, 2010, 27[10], 107901