Enhancement of Thermoelectric Performance in Bi_0.5Sb_1.5Te₃ Particulate Composites Including Ferroelectric BaTiO₃...

An increasing number of studies have reported producing composite structures by combining thermoelectric and functional materials. However, combining energy filtering and ferroelectric polarization to enhance the dimensionless figure of merit thermoelectric ZT remains elusive. Here we report a composite that contains nanostructured BaTiO₃ embedded in a Bi_0.5Sb_1.5Te₃ matrix. We show that ferroelectric BaTiO₃ particles are evenly composited with Bi_0.5Sb_1.5Te₃ grains reducing the concentration of free charge carriers with increasing BaTiO₃ content. Additionally, as a result of the energy-filtering effect and ferroelectric polarization, the Seebeck coefficient was improved by ∼10% with a ∼10% improvement in power factors. The BaTiO₃ phase can effectively scatters phonons reducing lattice thermal conductivity κ_l (0.5 W m^-1 K^-1) and increasing ZT to 1.31 at 363 K in Bi_0.5Sb_1.5Te₃ composites with 2 vol % BaTiO₃ content giving an improvement of ∼25% over pure Bi_0.5Sb_1.5Te₃. Our work indicates that the introduction of ferroelectric nanoparticles is an effective method for optimizing the ZT of Bi_0.5Sb_1.5Te₃-based thermoelectric materials.