Wu Yixuan, Nan Pengfei, Chen Zhiwei, Zeng Zezhu, Lin Siqi, Zhang Xinyue, Dong Hongliang, Chen Zhiqiang, Gu Hongkai, Li Wen, Chen Yue, Ge Binghui, Pei Yanzhong
Interdisciplinary Materials Research Center, School of Materials Science and Engineering, Tongji Univ., 4800 Caoan Rd., Shanghai 201804, China.
Institute of Physical Science and Information Technology, Anhui University, Hefei 230601, China.
Research (Wash D C). 2020 Jan 24;2020:8151059. doi: 10.34133/2020/8151059. eCollection 2020.
Maximizing band degeneracy and minimizing phonon relaxation time are proven to be successful for advancing thermoelectrics. Alloying with monotellurides has been known to be an effective approach for converging the valence bands of PbTe for electronic improvements, while the lattice thermal conductivity of the materials remains available room for being further reduced. It is recently revealed that the broadening of phonon dispersion measures the strength of phonon scattering, and lattice dislocations are particularly effective sources for such broadening through lattice strain fluctuations. In this work, a fine control of MnTe and EuTe alloying enables a significant increase in density of electron states near the valence band edge of PbTe due to involvement of multiple transporting bands, while the creation of dense in-grain dislocations leads to an effective broadening in phonon dispersion for reduced phonon lifetime due to the large strain fluctuations of dislocations as confirmed by synchrotron X-ray diffraction. The synergy of both electronic and thermal improvements successfully leads the average thermoelectric figure of merit to be higher than that ever reported for p-type PbTe at working temperatures.
事实证明，最大化能带简并度并最小化声子弛豫时间对于推进热电材料是成功的。已知与单碲化物合金化是一种有效的方法，可使PbTe的价带收敛以实现电子性能的改善，而材料的晶格热导率仍有进一步降低的空间。最近发现，声子色散的展宽衡量了声子散射的强度，而晶格位错是通过晶格应变涨落实现这种展宽的特别有效的来源。在这项工作中，对MnTe和EuTe合金化的精细控制使得由于多个输运能带的参与，PbTe价带边缘附近的电子态密度显著增加，同时，如同步加速器X射线衍射所证实的，由于位错的大应变涨落，晶内密集位错的产生导致声子色散有效展宽，从而降低了声子寿命。电子和热性能改善的协同作用成功地使平均热电优值高于在工作温度下p型PbTe所报道的任何值。
