High-pressure densified solid solutions of alkaline earth hexaborides (Ca/Sr, Ca/Ba, Sr/Ba) and their high-temperature thermoelectric properties

Journal Article · Thu Jan 15 04:00:00 EST 2015 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2014.10.001· OSTI ID:22443496

Gürsoy, M. ^[1]; Takeda, M. ^[2]

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1. Technische Universität Darmstadt, Eduard-Zintl-Institute of Inorganic and Physical Chemistry, Alarich-Weiss-Str. 12, 64287 Darmstadt (Germany)
2. Nagaoka University of Technology, Department of Mechanical Engineering, 1603-1 Kamitomioka, 940-2188 Nagaoka, Niigata (Japan)

Solid solutions of alkaline earth hexaborides were synthesized and densified by spark plasma sintering at 100 MPa. The high-temperature thermoelectric properties (Seebeck coefficients, electrical and thermal diffusivities, heat capacities) were measured between room temperature and 1073 K. CaB{sub 6}, SrB{sub 6}, BaB{sub 6} and the ternary hexaborides Ca{sub x}Sr{sub 1−x}B{sub 6}, Ca{sub x}Ba{sub 1−x}B{sub 6}, Sr{sub x}Ba{sub 1−x}B{sub 6} (x = 0.25, 0.5, 0.75) are n-type conducting compounds over the whole compositional and thermal ranges. The values of the figure of merit ZT for CaB{sub 6} (ca. 0.3 at 1073 K) were found to be significantly increased compared to earlier investigations which is attributed to the densification process. - Highlights: • Solid solutions of alkaline earth hexaborides were synthesized. • High-temperature thermoelectric properties of mixed calcium borides are excellent. • Spark plasma source densification results in high ZT values. • Borides are rare-earth free and refractory materials.

• OSTI ID: 22443496
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Vol. 221; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ALKALINE EARTH METALS
BARIUM BORIDES
CALCIUM BORIDES
PLASMA
PRESSURE RANGE MEGA PA 10-100
RARE EARTHS
SOLID SOLUTIONS
SPECIFIC HEAT
THERMAL DIFFUSIVITY
THERMOELECTRIC PROPERTIES