Ni doping and rational annealing boost thermoelectric performance of nanostructured double perovskite Pr_1.8Sr_0.2CoFeO₆

Pr₂CoFeO₆-based double perovskite exhibits intrinsic low thermal conductivity and high Seebeck coefficient, but its low electrical conductivity induces unsatisfied thermoelectric performance. Here, we employ a synergistic strategy of rational annealing and Ni doping to achieve an improved ZT of ∼0.085 at 573 K in Pr_1.8Sr_0.2CoFe_0.95Ni_0.05O₆, which is ∼425 % higher than that of pristine Pr₂CoFeO₆. The annealing process effectively reduces pores in the as-sintered bulk material, leading to an enhanced electrical conductivity without damaging the Seebeck coefficient, and the Ni doping further effectively improves the hole carrier concentration and in turn enhances the electrical conductivity, leading to a peak power factor of ∼113 μW m⁻¹ K⁻² at 573 K. Besides, Ni doping induces localized crystal imperfections including point defects, dislocations, and lattice distortions, contributing to an ultra-low thermal conductivity of <0.6 W m⁻¹ K⁻¹. As a result, the as-achieved Pr_1.8Sr_0.2CoFe_0.95Ni_0.05O₆ has a ZT of ∼0.085 at 573 K, which is highly competitive to reported thermoelectric double perovskites, indicating its potential applications in high-performance thermoelectric devices.