The effect of precursor boron nanopowder on the microstructure and emission properties of LaB6cathode materials

Abstract Two different structured boron sources have been used for the fabrication of LaB 6 ceramics and their effects on the sintering temperature, microstructure and emission properties were investigated. The results show that the reaction temperature of amorphous boron and La to form LaB 6 is 1200 °C, which is 150 °C lower than the reaction using crystalline boron. The grain size of LaB 6 prepared by amorphous boron and La is 150 nm, which is much smaller than that of crystalline boron ∼2 μm at the same sintering condition. With the grain size decreasing from 5 μm to 150 nm, the LaB 6 thermionic emission current density increases significantly and the field emission turn‐on field decreases from 1500 V to 1300 V. Using amorphous boron nanopowder can not only enhance the microstructure but also improve the emission properties. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)