Preparation and thermoelectric properties of B4C-Si-B composites

In this work B4C-Si-B composites have been prepared by spark plasma sintering (SPS) using different amount of B4C, B, and Si powders. The composition and the microstructure of the dense composites are characterized by means of XRD, SEM and EDX, the studies show that the composites contain BxSiyC and SiC phases with a homogenous structure. Moreover, the structure of the BxSiyC Phase is studied by Raman spectroscopy. The thermoelectric properties are investigated up to 1000 K. All samples are p-type semiconductors. A high Seebeck coefficient > 300 mu V/K is achieved at temperatures above 500 K. The electric conductivity of the composites increases with temperature and reaches a level > 15 S/cm. The formation of the new phases in the composite is found to decrease the thermal conductivity to < 10 W/mK. The greatest ZT value of 0.036 at 1000 K was obtained for the sample with 10 wt% Si and 5.6 wt% B.