Fabrication,characterization and thermionic emission properties of La0.2Ce0.8B6 single crystal

The multiple rare-earth hexaboride La0.2Ce0.8B6 single crystal with large size and high quality has been fabricated by the floating zone method.The（110）and（310）crystal surfaces of La0.2Ce0.8B6 are oriented by the X-ray Laue diffraction method and their thermionic emissions properties are measured.The results show that the maximum emission current densities of the（110）and（310）crystal surfaces at 1 673,1 773 and 1 873 Kare 3.60,7.73,12.44 A/cm2 and 3.25,11.67,16.93 A/cm2,respectively.It means that the thermionic emission is strongly anisotropic for the different crystal surfaces.The average value of effective work functions of（110）and（310）crystal surfaces at different temperatures are calculated to be 2.85 eV and 2.80 eV,indicating an excellent thermionic emission properties of La0.2Ce0.8B6 single crystal.