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Synthesis of Boron-Rich Metal Borides and Their Thermoelectric Properties

Published online by Cambridge University Press:  21 March 2011

Masatoshi Takeda
Affiliation:
Department of Mechanical Engineering, Nagaoka University of Technology, Kamitomioka, Nagaoka, 940-2188, Japan
Ferrer Domingo
Affiliation:
Department of Mechanical Engineering, Nagaoka University of Technology, Kamitomioka, Nagaoka, 940-2188, Japan
Takahiro Miura
Affiliation:
Department of Mechanical Engineering, Nagaoka University of Technology, Kamitomioka, Nagaoka, 940-2188, Japan
Tadahiro Fukuda
Affiliation:
Department of Mechanical Engineering, Nagaoka University of Technology, Kamitomioka, Nagaoka, 940-2188, Japan
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Abstract

Polycrystalline metal borides AlMgB14, CaB6, and MB2 (M: transition metals) were synthesized and their thermoelectric properties were examined. Single phase of orthorhombic AlMgB14, which contains B12 icosahedral clusters as building blocks, was obtained at sintering temperatures between 1573 K and 1823 K. Seebeck coefficient (α) and electrical conductivity (σ) of the phase were about 500 (μV/K) and 10−1 (1/Ωm) at room temperature, respectively. These values are comparable to those of metal-doped β- rhombohedral boron. Synthesized AlB2-type diborides (MB2; M=Ti, V, Cr, and Mn) exhibited metallic conduction. The MB2's α varied with number of valence electrons, and showed a maximum α in VB2. The variation was similar to that predicted for pseudogap system. The CaB6 also possessed metallic conduction, but the α of the phase was as large as 200 (μV/K) with negative sign.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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