Number of optical floating zone melting passes dependence of the LaB6 single crystals

• Effect of the number of optical floating zone melting passes on the LaB 6 single crystals was studied. • A truly [1 0 0] LaB 6 single crystal consisting of no sub-grains or twin crystals was grown. • Method of two optical floating zone melting passes is the most suitable for the growth of LaB 6 single crystal. LaB 6 materials, especially single crystals, are a kind of ideal cathode materials, however, the number of optical floating zone melting passes dependence of the LaB 6 single crystals are still unknown. In this paper, the effect of the number of optical floating zone melting passes on the crystal quality, purity and properties of LaB 6 single crystals has been investigated. It was found that a truly [1 0 0] LaB 6 single crystal consisting of no sub-grains or twin crystals was successfully grown regardless of how many zone melting passes. The crystal quality and purity have been verified to be gradually improved with the increase of the number of zone melting passes. It was particularly notable that there were very small differences in the content of impurity elements between as-grown crystals after two or three zone melting passes. The excellent performances of J 1kV = 42.22 A/cm 2 , J o = 28.99 A/cm 2 and Φ eff = 2.66 eV were belonged to LaB 6 single crystal after two zone melting passes, which indicates that the method of two optical floating zone melting passes is the most suitable at present for the growth of high-quality, high-purity and high-performance LaB 6 single crystals.