Unveiling transport properties in rare-earth-substituted nanostructured bismuth telluride for thermoelectric application

Abstract Thermoelectrics is an emerging technology in the field of renewable energy sources, and the exploration of doped materials has opened up new avenues for enhancing their performance. La-doped thermoelectric materials with the composition Bi 2− x La x Te 3 ( x = 0.0, 0.1, 0.2, 0.3, 0.4) were synthesized using the WOWS sol–gel method and sintered at 500 °C for 5 h. X-ray diffraction analysis confirmed a rhombohedral crystal structure with lattice constants of a = b = 4.41(2) Å and c = 29.81(3) Å. Scanning electron microscopy revealed particle-like shapes (0.7–2.5 μm). Fourier transform infrared spectroscopy confirmed the single-phase nature of the samples. DC electrical measurements showed increasing conductivity with temperature. AC electrical analysis demonstrated frequency-dependent behavior with increasing AC conductivity and decreasing loss factor and dielectric constants. Seebeck coefficient measurements exhibited temperature-dependent behavior. Thermal transport properties showed increasing thermal conductivity and volumetric specific heat with temperature, while thermal diffusivity decreased. The composition Bi 1.9 La 0.1 Te 3 with x = 0.1 doping displayed lower thermal conductivity, higher electrical conductivity, and a higher ZT value, making it more suitable for thermoelectric applications. Furthermore, the sample Bi 1.8 La 0.2 Te 3 exhibited favorable characteristics for energy storage applications compared to the other samples. These findings provide insights into the potential applications of La-doped bismuth telluride compounds in thermoelectric and energy storage systems.