Crystal growth and thermionic emission properties of Ce1-x-yLaxPryB6 single crystals

CeB6-based quaternary rare-earth hexaboride single crystals Ce1-x-yLaxPryB6 (x = 0.1–0.4, y = 0.1–0.4) with Φ 5 mm × 35 mm were grown via the optical floating zone technique. The crystal structure, atomic composition and thermionic emission properties of Ce1-x-yLaxPryB6 single crystals were systematically studied. The results of XRD and X-ray Laue diffraction reveal that these single crystals are grown along the <100> direction. The X-ray rocking curve analysis shows that the lowest full-width at half-maximum (FWHM) of Ce1-x-yLaxPryB6 single crystals is only 0.036° for Ce0.4La0.4Pr0.2B6 single crystal, whose atomic structure is revealed and the lattice spacing is 0.414 nm. The maximum thermionic emission current density of 114.21 A/cm2 at 1600 °C and minimum effective work function of 2.62 eV at the same temperature are also belonged to Ce0.4La0.4Pr0.2B6 single crystal, which indicates that it has great application prospects as a promising hot cathode material.