Synergistic Optimization of the Electronic and Phonon Transports of N-Type Argyrodite AgSnGaSe ( = 0-0.6) through Entropy Engineering.

The argyrodite compound, AgSnSe (ATS), which is one of the promising thermoelectric (TE) candidates, is receiving growing attention in thermoelectrics recently. However, its TE performance is still low and phases are unstable as the temperature varies. In this work, inspired by entropy engineering, we eliminate the β/γ phase transformation at ∼355 K via alloying Ga, thus extending its high-temperature cubic phase from 320 to 730 K. In the meantime, the power factor (PF) enhances by 10% and lattice thermal conductivity (κ) reduces by 40% at 723 K. As a result, the value is boosted to ∼1.15 for AgSnGaSe, which stands high among the ATS systems. This proves that the entropy engineering is an effective approach to extend the high-temperature range for the cubic γ-phase and improve its TE performance simultaneously.