Ag掺杂n型Bi_(2)Te_(2.7)Se_(0.3)的层间相互作用增强和室温热电性能改善

Strengthened interlayer interaction and improved room-temperature thermoelectric performance of Ag-doped n-type Bi_(2)Te_(2.7)Se_(0.3)

采用Cu或Ag掺杂是提高n型Bi2Te3基合金热电性能的有效途径但Cu或Ag的掺杂行为仍不明确,其背后的作用机理还需要进一步证实本文对Ag掺杂n型Bi_(2)Te_(2.7)Se_(0.3)多晶热电材料的结构和输运性质进行了研究.拉曼和X射线光电子能谱分析表明,Ag离子位于间隙位置,并向邻近的Te(Se)转移电子.Ag与Te(Se)成键导致层间相互作用增强,载流子迁移率升高.由于Ag–Te(Se)成键,Bi_(2)Te_(2.7)Se_(0.3)多晶的本征Te(Se)空位形成得到缓解,进而逐渐将载流子浓度调节到较低水平,因此Bi_(2)Te_(2.7)Se_(0.3)的室温热电性能得到显著改善.与单一Bi_(2)Te_(2.7)Se_(0.3)相比,最优Ag掺杂Bi_(2)Te_(2.7)Se_(0.3)材料的室温热电优值ZT和制冷性能分别提高近60%和75%.

Doping n-type Bi2Te3-based alloys with Cu or Ag has been proven an effective way to improve their thermoelectric performance.However,the doping behavior is still not clear and the underneath mechanism needs more evidence to clarify.Herein,a study on the structure and transport properties of polycrystalline Ag-doped n-type Bi_(2)Te_(2.7)Se_(0.3) is performed.Raman and X-ray photoelectron spectroscopy analysis suggests that Ag ions are situated at the interstitial sites and transfer electrons to the neighbouring Te(Se).The newly established Ag–Te(Se)bonds lead to strengthened interlayer interaction and improved carrier mobility.Te(Se)vacancy,as an intrinsic feature in the polycrystalline Bi_(2)Te_(2.7)Se_(0.3) alloy,is alleviated due to the formation of Ag–Te(Se)bonds.The carrier concentration can be gradually adjusted to a lower level,at which largely improved roomtemperature thermoelectric performance is yielded.As a result,the room-temperature dimensionless figure of merit ZT value and cooling performance of the optimal Ag-doped Bi_(2)Te_(2.7)Se_(0.3) are enhanced by nearly 60%and 75%as compared with those of the pristine Bi_(2)Te_(2.7)Se_(0.3).