Thermoelectric power factors of nanocarbon ensembles as a function of temperature

Gruen, D.M. ; Bruno, P. ; Arenal, R. ; Routbort, J. ; Singh, D. ; Ming, X.

Resumen: Thermoelectric power factors of nanocarbon ensembles have been determined as a function of temperature from 400 to 1200 K. The ensembles, composed of mixtures of nanographite or disperse ultrananocrystalline diamond with B 4 C
B4C
, are formed into mechanically rigid compacts by reaction at 1200 K with methane gas and subsequently annealed in an argon atmosphere at temperatures up to 2500 K. The ensembles were characterized using scanning electron microscopy, Raman, x-ray diffraction, and high resolution transmission electron microscopy techniques and found to undergo profound nanostructural changes as a function of temperature while largely preserving their nanometer sizes. The power factors increase strongly both as a function of annealing temperature and of the temperature at which the measurements are carried out reaching 1 µW/K 2 ¿cm
1 µW/K2¿cm
at 1200 K without showing evidence of a plateau. Density functional “molecular analog” calculations on systems based on stacked graphene sheets show that boron substitutional doping results in a lowering of the Fermi level and the creation of a large number of hole states within thermal energies of the Fermi level [P. C. Redfern, D. M. Greun, and L. A. Curtiss, Chem. Phys. Lett. 471, 264 (2009)]. We propose that enhancement of electronic configurational entropy due to the large number of boron configurations in the graphite lattice contributes to the observed thermoelectric properties of the ensembles.

Idioma: Inglés

DOI: 10.1063/1.3103244

Año: 2009

Publicado en: JOURNAL OF APPLIED PHYSICS 105 (2009), 073710 [10 pp.]
ISSN: 0021-8979

Factor impacto JCR: 2.072 (2009)

Categ. JCR: PHYSICS, APPLIED rank: 24 / 107 = 0.224 (2009) - Q1 - T1

Tipo y forma: Article (Published version)