Realizing High Mechanical and Thermoelectric Performance of n-Type rGO/Bi2Te2.7Se0.3 Composite

Bismuth telluride selenide (Bi₂Te_2.7Se_0.3) is a commonly used n-type material for near room temperature thermoelectric applications. Synthesising Bi₂Te_2.7Se_0.3 (BTS) composites for the improvement in the thermoelectric performance has gained interest in recent years. In this work, BTS and BTS/reduced graphene oxide (BTS-X wt %, X = 0–9) materials were synthesised by mechanical alloying using a ball mill. Graphite was chemically transformed into graphene oxide (GO) and then subsequently reduced to reduced graphene oxide (rGO). We report that addition of a small quantity of rGO (X ≤ 5 wt %) into Bi₂Te_2.7Se_0.3 improved the thermoelectric performance by improving the charge carrier transport and suppressing the thermal transport at the BTS/rGO interface. Enhanced phonon scattering at the interface reduced the thermal conductivity to ~1.83 W/m K and improved the power factor ~2927 µW m^–1 K^–2 at 514 K for BTS-5 wt % rGO sample. The peak ZT (ZT_max) of ~0.82 at 514 K was obtained for the BTS-5 wt % rGO composite sample enhancing the peak ZT by ~14% from the pristine. Meanwhile, we observed the ZT average increases from ~0.55 (300–600 K) for BTS to ~0.75 (300–600 K) for BTS-5 wt % rGO sample. This improvement is mainly attributed to the improvement in the Seebeck coefficient and the reduction in the thermal conductivity of the composite material. Furthermore, the addition of rGO into BTS results into the improvement in the hardness of the composite material.