Improved thermoelectric efficiency of Sb₂Si₂Te₆ through yttrium-induced nanocompositing

Sb₂Si₂Te₆ is a promising 2D material for medium-temperature thermoelectric applications, with the thermoelectric figure of merit zT approaching 1 at 823 K. However, its widespread use has been limited by relatively low power factor values. In this study, we successfully enhanced the performance of Sb₂Si₂Te₆ by introducing Yttrium nanocomposites. This modification fine-tuned the carrier concentration and electrical conductivity, and increased the power factor up to 946 μW K^-1 at 570 K. Jonker plot analysis revealed that increased carrier concentration did not affect the intrinsic electronic properties. SEM and TEM analyses revealed that Y nano-compositing introduced secondary phases, reducing the lattice thermal conductivity to values close to simulated ones using the Debye-Callaway model. Sb_1.98Y_0.02Si₂Te₆ exhibited the highest zT of 1.49 at 773 K due to the ultralow lattice thermal conductivity of 0.29 W m^-1 K^-1 and a moderate power factor of 858 μW K^-1 at the same temperature. The single parabolic band (SPB) model suggests that with further optimization of the Fermi level and additional reduction in lattice thermal conductivity, the zT value could potentially increase to 1.55. These results demonstrate the potential of Y nanocompositing for enhancing Sb₂Si₂Te₆ as an efficient medium-temperature thermoelectric material.