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A2: Medium temperature materials

High thermoelectric performance in p-type SnTe via a synergistic band engineering and nanostructuring approach

G. Tan,1 L.-D. Zhao,1 F. Shi,1 J.W. Doak,1 S.-H. Lo,1 H. Sun,2 C. Wolverton,1 V. P. Dravid,1 C. Uher,2 and M. G. Kanatzidis1,3,*
1Northwestern University, USA; 2University of Michigan, USA; 3Argonne National Laboratory, USA

We report here that p-type SnTe (which is a poor thermoelectric material in itself) can achieve a figure of merit ZT of ~1.3 around 875 K via a synergetic band engineering and nanostructuring approach. Specifically, it is demonstrated that incorporation of Cd (~3 mol.%) in the structure of SnTe favorably modifies the valence band structure by: (a) minimizing the energy separation between the light-hole band at L point and the heavy-hole band at Σ point, which increases the hole density of states and enhances the Seebeck coefficient; and (b) enlarging the band gap, which is beneficial to attain a high performance at elevated temperatures by suppressing the minority carriers. We also show that the phonon propagation of SnTe-based material can be largely inhibited through CdS/ZnS nanostructuring on account of the intensified interfacial scattering, giving rise to a low lattice thermal conductivity. Consequently, the maximum ZTs reach ~1.1 and ~1.3 for 3 mol.% Cd-doped SnTe nanostructured with 2 mol.% CdS and ZnS, respectively.