Effective thermionic work function measurements of zirconium carbide using a computer-processed image of a thermionic projection microscope pattern

Journal Article · Tue May 01 00:00:00 EDT 1990 · Journal of Vacuum Science and Technology, A (Vacuum, Surfaces and Films); (USA)

DOI:https://doi.org/10.1116/1.576759· OSTI ID:6881867

Mackie, W A; Hinrichs, C H; Cohen, I M; Alin, J S; Schnitzler, D T; Carleson, P; Ginn, R; Krueger, P; Vetter, C G ^[1]; Davis, P R ^[2]

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1. Linfield Research Institute, Linfield College, McMinnville, OR (USA)
2. Department of Applied Physics and Electrical Engineering, Oregon Graduate Center, Beaverton, OR (USA)

We report on a unique experimental method to determine thermionic work functions of major crystal planes of single crystal zirconium carbide. Applications for transition metal carbides could include cathodes for advanced thermionic energy conversion, radiation immune microcircuitry, {beta}-SiC substrates or high current density field emission cathodes. The primary emphasis of this paper is the analytical method used, that of computer processing a digitized image. ZrC single crystal specimens were prepared by floating zone arc refinement from sintered stock, yielding an average bulk stoichiometry of C/Zr=0.92. A 0.075 cm hemispherical cathode was prepared and mounted in a thermionic projection microscope (TPM) tube. The imaged patterns of thermally emitted electrons taken at various extraction voltages were digitized and computer analyzed to yield currents and corresponding emitting areas for major crystallographic planes. These data were taken at pyrometrically measured temperatures in the range 1700{lt}{ital T}{lt}2200 K. Schottky plots were then used to determine effective thermionic work functions as a function of crystallographic direction and temperature. Work function ordering for various crystal planes is reported through the TPM image processing method. Comparisons are made with effective thermionic and absolute (FERP) work function methods. To support the TPM image processing method, clean tungsten surfaces were examined and results are listed with accepted values.

• OSTI ID: 6881867
• Journal Information: Journal of Vacuum Science and Technology, A (Vacuum, Surfaces and Films); (USA), Vol. 8:3; ISSN 0734-2101
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ZIRCONIUM CARBIDES
THERMIONIC EMISSION
CRYSTAL LATTICES
EXPERIMENTAL DATA
IMAGE PROCESSING
VERY HIGH TEMPERATURE
WORK FUNCTIONS
CARBIDES
CARBON COMPOUNDS
CRYSTAL STRUCTURE
DATA
EMISSION
FUNCTIONS
INFORMATION
NUMERICAL DATA
PROCESSING
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties