Synergistically improving the thermoelectric performance of In₂O₃ via a dual-doping and nanostructuring approach

Co-substitution along with nanostructuring is typically employed to optimize thermoelectric transport properties for the development of highly efficient n-type thermoelectric materials. However, an understanding of defect chemistry plays a vital role in choosing the right substituent for the matrix of the parent structure. We investigate the thermoelectric performance of In2O3 via dual doping with Zn and Ge co-substitution. A single-phase structure with nanosized grains has successfully been obtained with Zn and Ge co-substitution even at an 8% doping concentration, using high energy planetary ball milling followed by spark plasma sintering (SPS). Zn and Ge co-doping substantially improved electrical transport by enhancing carrier concentration, which resulted in an increased effective mass with modest carrier mobility achieved sufficiently high power factor value of 9.39 μW cm−1 K−2 at 973 K observed for an 8% doping concentration. Furthermore, reduction of lattice thermal conductivity is observed from the co-substitution because of mass fluctuation scattering of the phonons. The combined effect of dual doping, the selection of the right substituent and phase purity results in an improved figure of merit ZT value of 0.36 at 973 K. This study suggests that In2O3 can be a potential material for thermoelectric applications.