Incompletely Decomposed In4SnSe4 Leads to High-Ranged Thermoelectric Performance in n-Type PbTe

Additives in thermoelectric materials are conventionally considered as either extrinsic defects or second phases regardless of their dynamic processes. Herein, In4SnSe4, with inherent low thermal conductivity, is introduced into n-type PbTe. It is revealed that In4SnSe4 decomposes incompletely at high temperatures, in which around 80% of In4SnSe4 dissolves into InSe and Sn, while 20% forms as nano-precipitates. Benefiting from the incomplete decomposition, PbTe-0.1% In4SnSe4 presents superior thermoelectric performance compared to the stepwise and compositionally identical PbTe-0.4%InSe-0.1%Sn. The residual In4SnSe4 along with Sn and InSe jointly contribute to the synergetic optimization of carrier mobility and lattice thermal conductivity in PbTe-0.1%In4SnSe4. As a result, the room-temperature dimensionless figure of merit (ZT) of approximate to 0.4 and the ZT(ave) of approximate to 0.83 at 300-573 K are obtained, and an experimental maximum thermoelectric conversion efficiency (eta) of approximate to 2.5% (Delta T approximate to 400 K) is obtained, demonstrating significant research progress in n-type PbTe. This work indicates that the In4SnSe4 incomplete decomposition effectively decouples the electron and phonon transports in n-type PbTe and the strategy of utilizing the unstable additives is proven feasible. Additionally, more dynamic behaviors of additives are worth expecting and may promote more achievements for other thermoelectric systems.