异层等价离子双掺杂策略优化BiCuSeO的热电性能

doi:10.15541/jim20180303

摘要/Abstract

摘要：

选取BiCuSeO双亚层超晶格热电材料为研究对象, 通过La、Ag单掺杂和双掺杂两种方式等价取代[Bi₂O₂]²⁺亚层和[Cu₂Se₂]^2-亚层中的Bi、Cu位点, 并对其热电输运性能和缺陷调控机理进行研究, 结果发现：La-Ag双掺杂可以结合两种单掺杂的优势, 在适度提升载流子浓度的同时保持与纯样相当的载流子迁移率, 从而使电导率得到大幅度的提升。与此同时, La-Ag双掺杂可以引发能带收敛效应, 有助于同步获得较高的载流子迁移率和Seebeck系数, 最终使PF得到了优化; 另一方面, 由于点缺陷对载热声子的强烈散射作用, 样品的晶格热导率和总热导率进一步降低, 使最终ZT值也得到了优化。结果, La-Ag双掺杂样品的ZT值在755 K下达到0.46, 高于原始纯样(ZT=0.27)和单掺杂样品。该项研究表明La、Ag异层等价双掺杂策略可以实现BiCuSeO热电输运参数的协同调控与优化。

关键词: 异层双掺杂, BiCuSeO, 热电性能, 电热输运, 协同调控

Abstract:

Taking the dual-sublayer BiCuSeO superlattice thermoelectric material as an object, equivalent mono- and dual-doped samples were prepared by substitution of Bi and Cu atoms in the corresponding [Bi₂O₂]²⁺ sublayer and [Cu₂Se₂]^2- sublayer with isovalent La and Ag atoms. Their thermoelectric properties and the defect modulation mechanism were studied. The results showed that La-Ag dual-doped sample could combine the advantages of mono-doped samples to achieve an relative high carrier mobility while moderately increasing the carrier concentration, thereby maximizing the electrical conductivity. At the same time, it can also induce a potential band convergenceeffect, achieving the low average band effective mass and high density of states effective mass at the same time, which finally endowed Bi_0.98La_0.02Cu_0.98Ag_0.02SeO with simultaneous high carrier mobility and Seebeck coefficient, as well as the optimized power factor (PF=σS²). On the other hand, due to the strong point defect scattering on the heat-carrying phonons, the lattice and total thermal conductivities of these isovalent doped samples were further reduced, which finally optimized the figure of merit (ZT). As a result, a high ZT value of 0.46 was achieved at 755K in the La-Ag dual-doped sample, which was superior to that of the pristine sample (0.27 at 755 K) as well as the mono-doped counterparts. Present work demonstrates that heterolayer-isovalent dual-doping with La/Ag equivalent atoms in BiCuSeO can synergistically modulate its thermoelectric transport parameters with significantly improved thermoelectric performance.

Key words: heterolayer dual-doping, BiCuSeO, thermoelectric property, electrical-thermal transport, synergistic modulation

中图分类号:

O472

李周, 肖翀. 异层等价离子双掺杂策略优化BiCuSeO的热电性能[J]. 无机材料学报, 2019, 34(3): 294-300.

LI Zhou, XIAO Chong. Optimizing Electrical and Thermal Transport Property in BiCuSeO Superlattice via Heterolayer-isovalent Dual-doping Approach[J]. Journal of Inorganic Materials, 2019, 34(3): 294-300.

图/表 6

图1 ZrSiCuAs型四方BiCuSeO的晶体结构示意图[16]

Fig. 1 Crystal structure of BiCuSeO with ZrSiCuAs-type tetragonal structure[16]

图2 Bi1-xLaxCu1-yAgySeO样品的XRD图谱(a), BiCuSeO样品的SEM照片(b), 沿[010]方向的HRTEM照片(c)及选区电子衍射花样(d)

Fig. 2 XRD patterns for Bi1-xLaxCu1-yAgySeO samples(a); SEM image (b), [010] HRTEM image (c) and SAED pattern (d) of pristine BiCuSeO

图3 La-Ag双掺杂样品的元素面分布mapping图像

Fig. 3 Element mapping of La-Ag dual-doping sample

图4 Bi1-xLaxCu1-yAgySeO样品的电导率(a), Seebeck系数(b)和热电功率因子PF(c) 随温度变化关系图; (d) 300 K下载流子浓度n和迁移率μ对比图

Fig. 4 Temperature-dependent electrical conductivity (a), Seebeck coefficient (b) and power factor of Bi1-xLaxCu1-yAgySeO samples; (d) Carrier concentration and mobility at 300K

图5 Bi1-xLaxCu1-yAgySeO样品的总热导率(a), 电学热导率和晶格热导率(b), 电学热导率占总热导率百分比(c)以及热电ZT值(d)随温度变化关系图

Fig. 5 Temperature-dependent total thermal conductivity (a), electrical and lattice thermal conductivities (b), percentage of electrical thermal conductivity (c) and dimensionless thermoelectric figure of merit (d) for Bi1-xLaxCu1-yAgySeO samples

图6 Bi1-xLaxCu1-yAgySeO样品的电子能带结构图(a), 吸收光谱(b)以及BiCuSeO带隙增大后轻、重价带靠近的示意图(c)

Fig. 6 Electrical band structure (a) and UV-Vis absorption spectra(b) of Bi1-xLaxCu1-yAgySeO samples, (c) Schematic representation of the convergence of heavy-light bands

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