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热电材料因其能够直接将热能转化为电能而具有广泛应用的前景。尽管最近几年发现了许多新型热电材料，但能够实现大规模商业化应用的依然是碲化铋(Bi2Te3)基材料。目前，Bi2Te3基材料的平均z T值和转化效率依然有提升空间。在本工作中，采用固相法和放电等离子烧结技术制备了p型(Bi,Sb)2Te3(BST)热电材料，并选取Na2S作为掺杂剂，实现了阳离子位置的低价取代，引入空穴，提升载流子浓度，优化BST基体热电材料的电导率。同时大量点缺陷增强声子散射降低材料热导率。除此之外S元素能够增强Na在BST基体中的固溶度，增强固溶强化。在300 K时0.5%(质量分数)Na2S掺杂的BST样品电导率由纯样品的598 S/cm提升至749 S/cm，同时样品的晶格热导率在300 K时降至0.55 W/(m·K)。由于功率因子的提升和热导率的降低，0.5%(质量分数)Na2S的BST样品在300 K的峰值zT达到1.3，较未掺杂样品提升了49.4%。由于其具有较优热电优值，在275 K的温差下单臂器件的热电转换效率达到了3%。另外，由于固溶强化掺杂样品的力学性能也得到较大提升，掺杂样品的平均硬度由纯样品的0.87 GPa提高到1.09 GPa，本工作的结果有望为其他热电材料的优化提供借鉴。
Abstract：Introduction Thermoelectric materials have a promising prospect as they can directly convert thermal energy into electrical energy.Some thermoelectric materials are discovered in recent years,especially bismuth telluride (Bi2Te3)-based materials that are capable of large-scale commercialization.At present,the average z T value and conversion efficiency of Bi2Te3-based materials can be further enhaced.The low-valent cation doping is achieved via doping to optimize the electrical conductivity,while introducing defects as phonon scattering centers to effectively reduce the lattice thermal conductivity.This strategy is verified to be the most effective optimization method.In this paper,Na2S was selected as a p-type dopant to dope Bi0.42Sb1.58Te3 (BST) alloys,the conductivity was optimized via replacing the cation position of the BST matrix,and improving the solid solubility of Na and strengthening its mechanical properties by element S.The lattice distortion caused by Na2S doping in the BST alloys and the nanopore structure generated by the volatile element Te in the matrix were investigated.Methods The original high-purity Bi powder (99.99%,in mass,the same below),Te powder (99.99%),Sb (99.99%),and Na2S powder (Aladdin Co.,China) were precisely weighed in an Ar atmosphere glove box based on their nominal composition(Bi0.42Sb1.58Te3+x%Na2S,where x=0,0.2,0.5,and 1.0).The weighed mixed powder was then placed in a quartz tube,evacuated to a vacuum degree of 10–4 Pa,and sealed.The quartz tubes were pre-plated with carbon to avoid the possibility of Na corrosion.The mixed powder in the sealed quartz tube was heated in a vertical resistance furnace for melting at 1125 K for 12 h and kept for 16 h.The ingots obtained after melting were ground by a model QM-3SP2 planetary ball mill at 425 r/min for 6 h.Finally,the powder was sintered at 698 K and 50 MPa by spark plasma sintering to prepare the bulk samples.The phase structure of the samples was analyzed by X-ray diffraction (XRD,Rigaku Co.,Japan) with Cu K_α radiation (λ=1.5406?) in a diffraction angle range of 20°–60°with a step size of 0.02°(5 (°)/min).The microstructure of the samples was examined by scanning electron microscopy (SEM,ZEISS Co.,Germany).The thermoelectric performance of the samples was analyzed via measuring their Seebeck coefficient,electrical conductivity,and power factor in a model ZEM-3M10 Seebeck coefficient/electric resistivity measuring system (Ulvac-Riko Co.,Japan) under a thin helium atmosphere.The thermal diffusivity of the samples was measured by a model LFA457 laser flash instrument (NETZSCH Co.,Germany),and the thermal conductivity was calculated based onκto t=DρCp,where D is the thermal diffusivity,Cp is the specific heat capacity deduced via the Dulong-Petit limit,andρis the density of samples.The density was determined according to the Archimedes principle.The carrier concentration and mobility of the samples were measured at 295 K under an applied magnetic field of 1.5 T and an electrical current of 30 mA in a model PPMS-9T physical properties measurement system (Quantum Design Inc.,Japan).Results and discussion When Na2S is used as a dopant,the electrical conductivity of 0.5%Na2S-doped BST sample increases from598 S/cm of the pure sample to 749 S/cm at 300 K,and the lattice thermal conductivity of the sample decreases to 0.55 W/(m·K) at300 K.The peak z T of 0.5%Na2S-doped BST sample reaches 1.3 at 300 K due to the increase of power factor and the decrease of thermal conductivity,which is 49.4%higher than that of the undoped sample.The thermoelectric conversion efficiency of the single-arm device reaches 3%asΔT=275 K due to its excellent thermoelectric figure of merit.In addition,the average hardness of the doped samples also increases to 1.09 GPa.Conclusions In this work,p-type BST thermoelectric materials were prepared by a solid-state method and a spark plasma sintering technology.Utilizing Na2S as a dopant achieved a low-valent substitution at cation sites,and introduced holes,thus enhancing the carrier concentration and optimizing the electrical conductivity of BST matrix thermoelectric materials.The peak z T of 0.5%Na2S-doped BST sample reached 1.3 at 300 K,which was 49.4%higher than that of the undoped sample.Furthermore,a large number of point defects enhanced phonon scattering and reduced the thermal conductivity of the material.In addition,element S could also enhance the solid solubility of Na in the BST matrix and the solid solution strengthening.The average hardness of the doped samples increased to 1.09 GPa.
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基本信息:
DOI：10.14062/j.issn.0454-5648.20240642
中图分类号:TB34
引用信息:
[1]俞江湖,石涌才,梁昊等.硫化钠掺杂提升碲锑铋材料热电性能和力学性能[J].硅酸盐学报,2025,53(04):748-758.DOI:10.14062/j.issn.0454-5648.20240642.
基金信息:
国家重点研发计划(2022YFF0503804)