Electronic transport in boron carbides

Journal Article · Tue Apr 15 04:00:00 EST 1986 · AIP Conf. Proc.; (United States)

DOI:https://doi.org/10.1063/1.35593· OSTI ID:5541469

Emin, D

The electronic transport of boron carbides, B/sub 1-x/C/sub x/ with 0.1< or =x< or =0.2, between 300K and 1200 K is inconsistent with conventional models of both itinerant and hopping transport. While the thermally activated conductivities and the low weakly activated Hall mobilities suggest the hopping of a high density (approx.10/sup 21/ cm/sup -3/) of small polarons, the spin densities are orders of magnitude smaller than this. Furthermore, the p-type Seebeck coefficients are both large (>100 ..mu..V/K) and strongly increasing functions of temperature, rather than being small and weakly temperature dependent as expected of degenerate semiconductors. Finally, unlike ''standard'' hopping systems, the electrical conductivity decreases with applied pressure. This is due to a pressure dependent increase of the conductivity activation energy. The anomalous thermoelectric, magnetic, and pressure-dependent transport properties are attributed to the charge carriers being hole-like small singlet bipolarons which hop between inequivalent B/sub 11/C icosahedra.

• Research Organization: Sandia National Laboratories, Albuquerque, New Mexico 87185
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 5541469
• Report Number(s): CONF-850786-
• Journal Information: AIP Conf. Proc.; (United States), Journal Name: AIP Conf. Proc.; (United States) Vol. 140:1; ISSN APCPC
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
&amp; Refractories-- Structure &amp; Phase Studies
BORON CARBIDES
BORON COMPOUNDS
CARBIDES
CARBON COMPOUNDS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRONIC STRUCTURE
HALL EFFECT
HIGH TEMPERATURE
MEDIUM TEMPERATURE
MOBILITY
PHYSICAL PROPERTIES
POLARONS
PRESSURE DEPENDENCE
QUASI PARTICLES
SEEBECK EFFECT
STRUCTURAL MODELS
TRANSPORT THEORY
VERY HIGH TEMPERATURE