Steric confinement for suppressing ion migration and boosting thermoelectric performance in Cu–S system via Ag and Se co-doping
Résumé
The Cu-S superionic compound exhibits excellent thermoelectric (TE) performance in the mid-temperature region. However, obtaining a thermally and electrically stable material in this system is still challenging. Herein, motivated by the perspective of steric confinement for suppressing Cu+ migration, we designed an Ag and Ag-Se co-doping strategy on pristine Cu1.93S to modulate the crystal structure. On one hand, Ag dopant is discovered to act as a vacancy filler, simultaneously optimizing carrier concentration and reducing thermal conductivity. Moreover, strategic Se co-substitution stabilizes Ag insertion within the Cu-S vacancy and induces non-negligible enhancement of phonon scattering to further reduce thermal conductivity. A competitive peak zT of 1.33@873 K was obtained for the Cu1.93Ag0.04S0.9Se0.1 sample at a relatively moderate temperature among current state-of-the-art Cu-S system. Moreover, thanks to the steric confinement, the Cu1.93Ag0.04S0.9Se0.1 composition exhibited superior electrical stability under dynamic DC-current compared to CuxS (with 1.93
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