Fabrication and Emission Property of Polycrystalline La0.4Pr0.6B6 Bulk Prepared by Spark Plasma Sintering

The LaH2 and PrH2 nanopowders were prepared by hydrogen arc plasma method, and then dense single-phase polycrystalline La0.4Pr0.6B6 bulks were reactively fabricated starting from mixture of synthesized LaH2, PrH2 nanopowders and boron powders by spark plasma sintering (SPS). The influence of SPS sintering temperature on the microstructure and properties was investigated. Thermionic emission measurement of the sample sintered at 1400℃ and 40MPa was performed. It is shown that the pure phase La0.4Pr0.6B6 bulk can be easily fabricated by SPS when the sintering temperature is higher than 1350℃ and the density of the material increases with increasing temperature. The largest values of densities, Vickers hardness and bend strengths reach 4.82g/cm3, 19.14GPa and 225.13MPa, respectively. The largest emission current density of the cathode heated at 1873K is 30.65A/cm2. The work function at absolute zero is calculated to be 2.165eV by Richardson line method, and then the average value of effective work functions of the cathode at different temperatures are calculated to be 2.84eV.