posted on 2021-07-28, 14:35authored byJuan Li, Qing Hu, Shan He, Xiaobo Tan, Qian Deng, Yan Zhong, Fujie Zhang, Ran Ang
The traditional thermoelectric material
GeTe has drawn much attention
recently because of the reported high thermoelectric performance of
the rhombohedral phase in low-temperature ranges, where the split L and Σ band can be reconverged to have a small energy
offset and thus high density of state effective mass according to
the rhombohedral angle. In addition, In doping in GeTe is also reported
to enhance the density of effective mass and therefore increase the
Seebeck coefficient because of the induced resonant levels. In this
work, In and Pb are doped in GeTe, and In doping leads to an increase
in the rhombohedral angle and thus enhanced density of state effective
mass in addition to the resonant effect. However, the improved Seebeck
coefficient result from In doping is compensated for by a sharp reduction
of Hall mobility, leading to no significant enhancement of electronic
performance in the rhombohedral phase. By further Pb/Ge doping in
the matrix Ge0.95In0.05Te for the optimization
of carrier concentration and reduction of lattice thermal conductivity
(as low as 0.7 W/mK), a zT as high as ∼1.2
at 550 K and average zT of ∼0.75 between 300
and 550 K are realized in this work, demonstrating GeTe as a promising
candidate for near-room-temperature application.