Journal Article

Enhancement of mechanical performance and reduction in thermal conductivity of Mg2Si-based thermoelectric nanocomposites through rGO addition

Pradhan, Abhishek, Ojha, Abhigyan, Bathula, Sivaiah, Nanda, Unanda

2024

Overview

Thermoelectric materials-based devices are used to convert heat energy into electrical energy. Magnesium silicide-based thermoelectric-based devices are considered commercially viable due to their low cost compared to other contemporary materials. The current study investigates the influence of Sb doping on the thermoelectric properties of the Mg2.15Si0.28Sn0.714Sb0.006 (Sample-A) compound with an excess Mg content (7.5 mol %). The excess Mg induces point defects through interstitial Mg and Si/Sn vacancies, significantly enhancing the electron concentration (ne). Moreover, Sb is recognized as an effective single-electron donor in Mg2Si-based materials, leading to notable increases in ne and electrical conductivity. Consequently, in the current investigation, excess Mg combined with appropriate Sb doping, resulted in the selection of Mg2.15Si0.28Sn0.714Sb0.006 (Sample-A), which exhibited high ne and superior thermoelectric performance. Further, the current study was extended by incorporating 3 vol.% of reduced graphene oxide (rGO) into Mg2.15Si0.28Sn0.714Sb0.006 + 3 vol.% rGO (Sample-B) to enhance mechanical performance and reduce thermal conductivity (k). Consequently, Sample-B showed a ∿ 28% increase in fracture toughness (from 1.48 to 1.9 MPa√m) and a ∿ 137% improvement over conventional Mg2Si. Moreover, the inclusion of rGO resulted in a substantial reduction in k ∿ 40% in the mid-temperature range, due to intensified phonon scattering caused by the higher interface density within the matrix. However, adding more than 3 vol.% rGO negatively impacts both thermoelectric and mechanical properties by obstructing the charge carriers. Therefore, achieving an optimal balance between rGO addition and compositional modulation is essential to enhance both thermoelectric and mechanical performance in these composites.

• Publisher: Springer Nature B.V
• Subject: Alternative energy / Antimony / Composite materials / Crack propagation / Current carriers / Doping / Efficiency / Electrical resistivity / Energy resources / Fracture toughness / Graphene / Heat conductivity / Heat transfer / Intermetallic compounds / Magnesium compounds / Mechanical properties / Metal silicides / Nanocomposites / Plasma sintering / Point defects / Silicides / Silicon / Single electrons / Solid solutions / Temperature / Thermal conductivity / Thermoelectric materials / Tin