Investigation of microstructure and thermoelectric properties of p-type BiSbTe/ZnO composites

In this research work, p-type BiSbTe/ZnO (2 wt%) nanocomposite powders were fabricated by high-energy ball milling at different milling times, and subsequently, powders were consolidated by spark plasma sintering at 673 K temperature. The existence of nanoinclusions was confirmed by SEM-EDS mapping. Vickers hardness values greatly improved due to reduction in grain size which prevents the crack propagation and dispersion strengthening mechanism. The decrease in carrier density, which plays a critical role in thermoelectrics, dramatically increases the Seebeck coefficient, and subsequently, decreases the electrical conductivity upon the dispersion of ZnO nanorods into the BiSbTe matrix. The thermal conductivity was noticeably reduced by similar to 13% in BiSbTe/ZnO composites for 5-minute samples due to blocking of carriers/phonons at interfaces, and/or grain boundaries. The peak ZT of 0.92 was obtained for BiSbTe matrix, and 0.91 for BiSbTe/ZnO (5 minutes) composites at room temperatures.