Spark Plasma Sintered Bulk Nanocomposites of Bi₂Te_2.7Se_0.3 Nanoplates Incorporated Ni Nanoparticles with Enhanced Thermoelectric Performance

Bi2Te3-based compounds are important near room temperature thermoelectric materials with commercial applications in thermoelectric modules. However, new routes leading to improved thermoelectric performance are highly desirable. Incorporation of superparamagnetic nanoparticles was recently proposed as a means to promote the thermoelectric properties of materials, but its feasibility has rarely been examined in mainstream thermoelectric materials. In this study, high quality single-crystalline Bi2Te2.7Se0.3 nanoplates and Ni nanoparticles were successfully synthesized by solvothermal and thermal decomposition methods, respectively. Bulk nanocomposites consisting of Bi2Te2.7Se0.3 nanoplates and superparamagnetic Ni nanoparticles were prepared by spark plasma sintering. It was found that incorporation of Ni nanoparticles simultaneously increased the carrier concentration and provided additional scattering centers, which resulted in enlarged electric conductivities and Seebeck coefficients. The greatly improved ZT was achieved due to the increase in power factor. Spark plasma sintered bulk nanocomposites of Bi2Te2.7Se0.3 nanoplates incorporated by 0.4 mol %Ni nanoparticles (in molar ratio) showed a figure-of-merit ZT of 0.66 at 425 K, equivalent to 43% increase when compared to pure Bi2Te2.7Se0.3 nanoplates. The results revealed that incorporation of magnetic nanoparticles could be an effective approach for promoting the thermoelectric performance of conventional semiconductors.