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, β‐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<T<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.
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Research Article|
May 01 1990
Effective thermionic work function measurements of zirconium carbide using a computer‐processed image of a thermionic projection microscope pattern
William A. Mackie;
William A. Mackie
Linfield Research Institute, Linfield College, McMinnville, Oregon 97128‐6984
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Clarence H. Hinrichs;
Clarence H. Hinrichs
Linfield Research Institute, Linfield College, McMinnville, Oregon 97128‐6984
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Ira M. Cohen;
Ira M. Cohen
Linfield Research Institute, Linfield College, McMinnville, Oregon 97128‐6984
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John S. Alin;
John S. Alin
Linfield Research Institute, Linfield College, McMinnville, Oregon 97128‐6984
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Don T. Schnitzler;
Don T. Schnitzler
Linfield Research Institute, Linfield College, McMinnville, Oregon 97128‐6984
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Pete Carleson;
Pete Carleson
Linfield Research Institute, Linfield College, McMinnville, Oregon 97128‐6984
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Robert Ginn;
Robert Ginn
Linfield Research Institute, Linfield College, McMinnville, Oregon 97128‐6984
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Peter Krueger;
Peter Krueger
Linfield Research Institute, Linfield College, McMinnville, Oregon 97128‐6984
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Catharine G. Vetter;
Catharine G. Vetter
Linfield Research Institute, Linfield College, McMinnville, Oregon 97128‐6984
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Paul R. Davis
Paul R. Davis
Department of Applied Physics and Electrical Engineering, Oregon Graduate Center, Beaverton, Oregon 97006‐1999
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J. Vac. Sci. Technol. A 8, 2333–2337 (1990)
Article history
Received:
August 21 1989
Accepted:
October 09 1989
Citation
William A. Mackie, Clarence H. Hinrichs, Ira M. Cohen, John S. Alin, Don T. Schnitzler, Pete Carleson, Robert Ginn, Peter Krueger, Catharine G. Vetter, Paul R. Davis; Effective thermionic work function measurements of zirconium carbide using a computer‐processed image of a thermionic projection microscope pattern. J. Vac. Sci. Technol. A 1 May 1990; 8 (3): 2333–2337. https://doi.org/10.1116/1.576759
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