Enhanced thermoelectric properties of Bi₂Te_2.55Se_0.45 nanocomposites using eco-friendly Eocene Midra Shale palygorskite nanofillers: A sustainable approach

This paper investigates the influence of incorporating Eocene Midra Shale (EMS), consisting of 1D palygorskite and 2D irregular dolomite flakes, on the thermoelectric properties of an n-type Bi2Te2.55Se0.45 alloy. The EMS was obtained from one of Qatar's substantial hydrocarbon reservoirs and mixed with the Bi2Te2.55Se0.45 alloy using ball-milling and hot-pressing techniques. Different wt% of EMS (0.025, 0.05, 0.1, 0.5, and 1) were considered. TEM analysis of the composite samples revealed the incorporation of palygorskite fibers within the Bi2Te2.55Se0.45 particles, while dolomite nanoflakes were observed at the boundaries. The distinct effects of the present minerals were evident in the thermoelectric properties of the EMS-Bi2Te2.55Se0.45 composites. Incorporating a small quantity of EMS (0.05 wt%) has enhanced the electrical conductivity of the samples relative to the pristine ones, demonstrating the effectiveness of palygorskite nanofibers in facilitating charge carrier transport. However, adding higher amounts (0.1, 0.5, and 1) decreased the electrical and thermal conductivities due to the dominant effect of bulky precipitates in increasing the scattering of charge carriers and phonons. The calculated ZT profile showed that EMS can improve the thermoelectric properties only when added in small amounts of 0.05 wt%. The figure-of-merit of the 0.05 wt% sample reached 0.89 at 150 degrees C, resulting in 19 % improvements compared to the pristine Bi2Te2.55Se0.45 pellet measured at the same temperature. This performance surpassed both the pristine sample and reference nanocomposites with graphene and MXene. These results highlight EMS as a low-cost, natural nanofiller with strong potential for scalable thermoelectric applications.