Abstract
Barium hexaboride was prepared by the borothermic reaction using BaCO3 and B powders as starting materials. The formation process of BaB6 consists of two steps: BaCO3 + 7B→BaB2O+ + A + CO2↑ (800 °C), and BaB2O4 + A →BaB6 + 0.5B2O2↑ (1300 °C), where A is an unknown phase whose main component is considered to be boron. BaB6 powder consists of fine crystals having cubic shapes. The vapor pressure and thermionic emission current are greatly affected by the surface structure of the BaB6 powder. BaB6 powder with a thin oxide layer has a Ba vapor pressure and thermionic emission current density as much as nearly two orders of magnitude higher than BaB6 powder with a clean surface obtained by heating to a temperature over 1100 °C. These properties are remarkably influenced both by exposing the powder to the atmosphere and by introducing O2 gas during measurement. These phenomena are interpreted by considering the strong affinity of Ba and B for oxygen, the preferential vaporization of B2O2 gas, and the formation of a Ba monolayer on slightly oxidized BaB6 powder surfaces, which is generated from the reaction of BaO and B and lowers the work function.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
