Interplay of densification and RGO encapsulation in boosting thermoelectric properties of indium tin oxide

Abstract Tin-doped indium oxide (ITO) is a widely used transparent conducting oxide. Due to its high electrical conductivity and thermal stability, it is a potential candidate for thermoelectric (TE) applications. However, it remains underexplored, as the high thermal conductivity of this degenerate semiconductor limits its TE performance. In some cases, using a carbon-based material such as RGO, graphene, graphite, or carbon nanotubes has been proven to be a key strategy for enhancing the TE performance of degenerate semiconductors. RGO has been previously used during the synthesis of oxide nanoparticles to mitigate grain boundary resistance, control the band structure, and enhance phonon scattering. In this work, the TE performance of the 10 at% Sn-doped In ₂ O ₃ has been investigated, focusing on the interplay between densification and RGO encapsulation. Both room-temperature and high-temperature densification are performed to examine their influence on TE properties via modulation of density and microstructure. The results from the measurements confirm that RGO encapsulation, coupled with hot-pressing, significantly improves electrical conductivity and reduces thermal conductivity, enabling a better overall zT while maintaining high density. This study presents an effective strategy to improve the high-temperature TE properties of n -type degenerate semiconducting oxides, such as ITO, by nanostructurization via inclusion of carbon-based material. The high-temperature densification using hot-press (HP) allows the RGO composite to exhibit a higher density (93% of the In ₂ O ₃ theoretical density), thereby improving mechanical properties and making it more suitable for forming low-resistance device contacts. Moreover, the high density, coupled with a power factor of around 180 µ W (m K ² ) ⁻¹ for the HP ITO–RGO composite, is significantly higher than that of their room-temperature densified counterparts, making these more suitable for device output.