Stepwise Alloying in Liquid-like Solid Solutions to Achieve Crystallographic Distortion for Regulating Thermoelectric...

With the surge of energy consumption, environmental-protection Cu_2-Se thermoelectric materials are increasingly attracting attention. In this work, multilayered structures are constructed in Cu_2-Se solid solutions by alloying (SnSe)_0.75(AgBiSe₂)_0.25, which strongly scatters full-wavelength phonons by carefully regulating the crystallographic distortion. By using the stepwise alloying strategies, crystallographic distortion and the resultant strain fields presented in microstructure were strengthened markedly, which enhanced the phonon scattering. Meanwhile, by adjusting the coalloying content of Ag, Bi, and Sn elements, the carrier and phonon transports were well decoupled in p-type Cu_2-Se, and the thermoelectric performance was significantly enhanced. By optimized power factor as well as depressed heat transport originating from the moderate coalloying, the maximum zT of 1.23 at 750 K was achieved in Cu_1.9Se - 1 wt % (SnSe)_0.75(AgBiSe₂)_0.25. This study indicated that the stepwise alloying strategy was a suitable method for optimizing zT of Cu_2-Se.