Fabrication and characterization of rare earth hexaboride single-crystal materials
Oriented single crystals of LaB/sub 6/, CeB/sub 6/ and PrB/sub 6/ were prepared by the arc float-zone refining technique, which is described. A critique of the various possible preparation techniques is given. Wet chemical methods were used to determine bulk stoichiometries of samples prepared from starting materials of various R/B compositions (where R = rare earth). It was found that LaB6.09, a desired composition, could be grown in single-crystal form from LaB6.2 starting material, the excess boron compensating for preferential boron vaporization. Starting materials with B/La < 6.2 produce a B/La gradient in two-pass zone-refined specimens. The level of metallic impurities in arc zone-refined LaB/sub 6/ is lower than that reported elsewhere for laser zone-refined LaB/sub 6/. Residual oxygen present in the zone-refined specimens was found to produce second-phase inclusions, which were studied in detail. The effect of contamination of LaB/sub 6/ surfaces by evaporated refractory metals was also investigated.
- Research Organization:
- Oregon Graduate Center, Beaverton (USA). Dept. of Applied Physics and Electronic Science
- OSTI ID:
- 6117683
- Report Number(s):
- AD-A-181410/2/XAB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
ALLOYS
BORIDES
BORON COMPOUNDS
CATHODES
CERIUM BORIDES
CERIUM COMPOUNDS
CONTAMINATION
CRYSTAL DEFECTS
CRYSTAL GROWTH
CRYSTAL STRUCTURE
ELECTRODES
ELEMENTS
FABRICATION
IMPURITIES
LANTHANUM BORIDES
LANTHANUM COMPOUNDS
MELTING
METALS
MICROSTRUCTURE
NONMETALS
OXYGEN
PHASE TRANSFORMATIONS
PRASEODYMIUM BORIDES
PRASEODYMIUM COMPOUNDS
PROCESSING
RARE EARTH COMPOUNDS
REFINING
REFRACTORY METALS
STOICHIOMETRY
ZONE MELTING