Tuning Interstitials in Fully Dense β-Zn₄Sb₃ Doubles Single-Leg Thermoelectric Efficiency

Zinc antimonides, particularly the β-Zn₄Sb₃ compound, act as prototypes in the early phases of thermoelectric generator (TEG) development. However, their potential applications are constrained by structural instability at elevated temperatures. In this study, introducing a low concentration of aluminum (Al) achieves a highly stable Al-Zn₄Sb₃, exhibiting an improved peak zT value compared to undoped Zn₄Sb₃. Notably, a single-leg device utilizing a fully dense Al_0.01Zn_3.99Sb₃ demonstrates an impressive conversion efficiency (η) of 3% even at a temperature difference (ΔT) of 225 K. This result represents an approximately 200% increase compared with the pristine one. The combination of dilute cationic doping and phase diagram engineering solidifies the potential of Zn₄Sb₃ as an efficient and sustainable green energy device.