ICT2014 Abstracts

Cu-Zn-S nanoparticles are an interesting material for low temperature and sustainable thermoelectrics because of the potentially tunable nature of its semiconducting properties. By controlling the material composition the electrical conductivity and Seebeck properties can be manipulated while the nano-scale particle size allows suppression of thermal conductivity. To study the system, we prepared Cu-Zn-S nanoparticles using a wet-chemical thermolysis technique which allowed the particle composition to be tuned. The resulting particles display a hexagonal multi-faceted morphology with a size of about 5 to 10 nm. The results showed that as the feeding ratio of Zn was increased in the particle synthesis, the particles became increasingly phase segregated, leading to heterostructured Cu₂S-ZnS Janus nanoparticles. The samples were prepared for thermoelectric characterization and the typically low electrical conductivity for pressed nanoparticle samples was overcome by first functionalizing the particle surfaces in conductive organic molecules, pressing, and successive thermal treatment to induce partial sintering. The results revealed remarkable semiconducting properties for the Janus nanomaterial where pure Cu₂S nanoparticles possess a Seebeck coefficient of 145 µV/K which decreases for the Janus particles and approaches 0 as the ZnS content is increased. The results indicate that while the pure Cu₂S nanoparticles possess a reasonable Seebeck value, the Janus particles display suppressed Seebeck activity as a result of P-N junctions existing within independent particles. The results reveal insight and have implications to designing the next generation of active, low-temperature and sustainable thermoelectric materials composed of nanoparticles. The results will be discussed in terms of the synthetic and preparation methods used as well as the characterization of the particles and resulting thermoelectric materials properties.