Thermoelectric Transport Performance in p-Type AgSbTe-Based Materials through Entropy Engineering.

Being a major obstacle, AgTe has always been restricted in p-type AgSbTe-based materials to improve their thermoelectric performance. This work reveals a stabilized AgSbTe through Sn/Ge alloying as synthesized by melting, annealing, and hot press. Interestingly, addition of Sn/Ge in AgSbTe extended the solubility limit up to ∼30% and hence suppressed AgTe in AgSnSbGeTe compounds and led to enhanced electrical transport. Moreover, electrical and thermal transport properties of AgSbTe have been greatly affected by the phase transition of AgTe near 425 K. However, high-entropy AgSnSbGeTe compound results in a stabilized rock-salt structure and presents a high power factor of ∼10.8 μW cm K at 757 K. Besides, density functional theory reveals that available multivalence bands in Sn/Ge-doped AgSbTe lead to reduction in energy offsets. Meanwhile, a variety of defects appear in the AgSnSbGeTe sample due to entropy change, and thus lattice thermal conductivity decreases. Ultimately, a high figure of merit of ∼1.5 is attained at 757 K. This work demonstrates a roadmap for other group IV-VI materials so that the high-entropy approach may inhibit the impurity phases with extended solubility limit and result in high thermoelectric performance.