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X-ray Diffraction Studies of the Structure and Thermochemistry of Alkaline-Earth Oxide-Coated Thermionic CathodesNASA LeRC has a broad, active cathode technology development program in which both experimental and theoretical studies are being employed to further development of thermionic cathodes for use as electron sources in vacuum devices for communications and other space applications. One important type of thermionic cathode under development is the alkaline-earth oxide-coated (BaO, SrO, CaO) cathode. Significant improvements in the emission characteristics of this cathode have been obtained through modification of the chemical composition and morphology of the oxide coating, with the best result thus far coming from the addition of In2O3 and Sc2O3. Whereas the In2O3 produces a finer, more uniform particle structure, the exact chemical state and role of the Sc2O3 in the emission enhancement is unknown. The purpose of this cooperative agreement is to combine the studies of the surface chemistry and electron emission at NASA LeRC of chemically modified oxide coatings with a study of the thermochemistry and crystal structure using X-ray diffraction equipment and expertise at Clark Atlanta University (CAU). The study at CAU is intended to provide the description and understanding of the structure and thermochemistry needed for further improvement and optimization of the modified coatings. A description of the experimental procedure, preliminary X-ray diffraction test results, together with the design of an ultrahigh vacuum chamber necessary for high temperature thermochemistry studies will be presented.
Document ID
Document Type
Conference Paper
Karikari, E. K.
(Clark-Atlanta Univ. GA United States)
Bassey, E.
(Clark-Atlanta Univ. GA United States)
Wintucky, Edwin G.
(NASA Lewis Research Center Cleveland, OH United States)
Date Acquired
August 18, 2013
Publication Date
April 1, 1998
Publication Information
Publication: HBCUs Research Conference Agenda and Abstracts
Subject Category
Electronics And Electrical Engineering
Distribution Limits
Work of the US Gov. Public Use Permitted.

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