Electrical conductivity of boron carbide from ∼5 to ∼2100 K in the whole homogeneity range

• Published in: Solid state sciences Vol. 132; p. 106987
• Main Authors: Werheit, Helmut, Herstell, Bernhard, Winkelbauer, Walter, Pristáš, Gabriel, Gabáni, Slavomir, Flachbart, Karol, Shalamberidze, Sulkhan
• Format: Journal Article
• Language: English
• Published: Elsevier Masson SAS 01-10-2022
• Subjects: Boron Carbide; Electrial Conductivity; Electronic Properties; Hopping Conductivity; Electronic Properties; Electrial Conductivity; Hopping Conductivity; Boron Carbide
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2022.106987

Though controversially discussed, understanding of the electronic properties of B4.3C, carbon-rich limit of the homogeneity range has meanwhile reached an advanced degree. In contrast, the knowledge on more boron-rich boron carbides has remained small. As a contribution for closing this gap, we present a study of the electrical conductivity from ∼5 to ∼2100 K. Numerous samples covering the whole homogeneity range came from various sources and were differently prepared, thus allowing to separate intrinsic effects from those of impurities, density and preparation method. We show that at low temperature, the electrical conductivity meets formally Mott's law of variable-range hopping. However, its parameters are incompatible with experimental results and need redefinition. At high temperatures, the electrical conductivity is thermally activated. The activation energies yield the energetical position of gap states above the valence band, which are related to intrinsic defects in the structure depending on the actual chemical composition.
Electrical conductivity of B4.3C boron carbide. [Display omitted]
•The electrical conductivity of boron carbide is studied between 5 and 2100 K in the whole homogeneity range.•Effects of various structural defects are recognized.•Specific gaps states are identified acting at high and low T in different function, each.•At high T the electrical conductivity is thermally activated, while at low T Mott's law of variable range hopping is formally met.•In the case of boron carbide, the parameter σ0 of Mott's law require redefinition.