Floating Zone Growth and Thermionic Emission Property of Single Crystal CeB₆

Large-sized and high-quality cerium hexaboride (CeB₆) single crystals are successfully grown by the optical floating zone method. The structure, chemical composition and thermionic emission properties of the crystal are characterized by x−ray diffraction, x-ray fluorescence and emission measurements, respectively. Based on the observation of single crystal diffraction, the relative density of feed rods has a great effect on the quality of the grown crystal. The thermionic emission measurement results show that the emission current density of the single crystal is 47.1 A/cm² at 1873 K with an applied voltage of 1 kV, which is about two times larger than the value for polycrystalline samples. The single crystal possesses excellent emission current stability. Therefore, it is expected that CeB₆ single crystal is a very promising material for thermionic cathode applications.