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In situ preparation and thermoelectric properties of B4C1-x-TiB2 composites

: Feng, B.; Martin, H.-P.; Michaelis, A.


Journal of Electronic Materials 42 (2013), Nr.7, S.2314-2319
ISSN: 0361-5235
ISSN: 1543-186X
Fraunhofer IKTS ()

B4C1-x-TiB2 composites were prepared by in situ reactive spark plasma sintering of B4C with addition of nano-TiO2 powder. The effect of TiO2 addition on the sinterability of boron carbide was studied. The composition and the microstructure of the dense composites are characterized by means of x-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX). The studies show that the composites contain boron carbide and TiB2 phases with a homogeneous structure. In addition, the correlation between the composition and the thermoelectric properties was investigated. The electrical conductivity of the composite increased with increasing addition of TiO2 and the Seebeck coefficient decreased with TiO2 addition. The percolation threshold øc for TiB2 in the B4C1-x-TiB2 system was found to be in the range of 0.139 to 0.189. The thermal conductivity was reduced in the whole measuring temperature range from 50 C to 800 C below øc. Accor dingly, a significant enhancement in the dimensionless figure of merit ZT of the composites was achieved compared with that of boron carbide without TiO2 addition, with ZT achieving its maximum value at 10 wt.% TiO2.