Configurational, electronic entropies and the thermoelectric properties of nanocarbon ensembles

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Reaction of disperse ultrananocrystalline diamond (UNCD) and mixtures of UNCD containing 10%-20% nanoboron carbide (B4 C) with methane gas at temperatures near 1200 K results in mechanically rigid compacts called nanocarbon ensembles (NCE) and boron-doped NCE, respectively. Seebeck coefficient and electrical conductivity results lead to strongly temperature dependent power factors that increase 30-40 fold for boron containing ensembles compared to undoped material. It is likely that boron substitutional doping of nanographite crystallites results in a multiplicity of electronic states within a narrow energy band around the Fermi level leading to an increase in configurational electronic entropy. © 2008 American Institute of Physics.

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Applied Physics Letters