Single crystal LaB/sub 6/
Single crystals of LaB/sub 6/ were prepared by float zone refining of hot pressed blocks of LaB/sub 6/. The orientations studied were (001), (110), and a high index plane. The resulting crystals and the as-received material were chemically analyzed by vacuum fusion, combustion analysis, self-arc mass spectroscopy, and wet chemical analysis. The first two provided accurate analysis for O, N, H, and C. The remaining elements except for La and B were determined by mass spectroscopy. The wet chemical analyses determined the B/La ratio. Two batches of as-received material had B/La ratios of 6.0 and 5.8, respectively. Slightly lower B/La ratios were obtained in the single crystals grown by the float zone technique from these materials. The single crystals were further characterized by measurements of lattice parameter and density. Work function values were determined by the FERP method and the thermionic method. Work function measurements in conjunction with Auger analysis of the crystals provided insight into the electron emission character of LaB/sub 6/. Results indicate that for maximum emission from a crystal plane a proper heat treatment is necessary. Brightness of the crystals was measured in a Cambridge S-4 scanning electron microscope using a Broers type gun. Results show that a brightness of 10/sup 6/ amp/cm/sup 2/ steradian (20kV) may be achieved with a single crystal LaB/sub 6/ cathode operating at a temperature of 1900/sup 0/K which corresponds to a lifetime greater than 500 hrs for 1 mm cathodes.
- Research Organization:
- Ames Lab., Ames, IA (United States)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 5897601
- Report Number(s):
- IS-T-869; TRN: 79-019394
- Resource Relation:
- Other Information: Thesis
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
LANTHANUM BORIDES
CRYSTAL GROWTH
OPTICAL PROPERTIES
ZONE REFINING
CHEMICAL ANALYSIS
DENSITY
ELECTRON EMISSION
HEAT TREATMENTS
LATTICE PARAMETERS
MONOCRYSTALS
ORIENTATION
WORK FUNCTIONS
BORIDES
BORON COMPOUNDS
CRYSTALS
EMISSION
LANTHANUM COMPOUNDS
PHYSICAL PROPERTIES
PROCESSING
RARE EARTH COMPOUNDS
REFINING
SEPARATION PROCESSES
360201* - Ceramics
Cermets
& Refractories- Preparation & Fabrication
360202 - Ceramics
Cermets
& Refractories- Structure & Phase Studies
360204 - Ceramics
Cermets
& Refractories- Physical Properties