One–One Correspondence between n-Type SnTe Thermoelectric and Topological Phase Transition

Abstract

A lot of thermoelectric materials (TE) have been proved as topological crystalline insulators (TCIs), like SnTe, although the internal connection of thermoelectric and topological states has remained unclear. Herein, we deeply and experimentally verified the one–one correspondence between the n-type SnTe thermoelectric and topological phase transition. The challenging n-type SnTe could only be realized after the topological phase transition from topologically nontrivial phase to topologically trivial phase, induced by Pb alloying via tuning the L6+ and L6− states in the band edge at the L point in the Brillouin zone, followed by donor doping via Br, pushing the Fermi level into the conduction band. Outstanding ZTmax of ∼0.7 and ∼0.8 at 573 K and excellent ZTave of ∼0.42 and ∼0.58 at 300–823 K are achieved for the n-type Sn0.6Pb0.4Te0.9875Br0.0125 polycrystal and the SnTe–Pb–Br crystal, respectively. Our work explored the significant n-type SnTe from the combined bulk and surface states aspects and experimentally revealed that the thermoelectric, especially the conductivity, behavior is directly and profoundly influenced by the topological phase transition in the SnTe TE/TCI system, which will inspire further researches on other TE/TCI materials and thermoelectric devices with p- and n-type SnTe legs.