AgI掺杂量对n型Bi2Te2.85Se0.15材料热电性能的影响

采用机械合金化(MA)结合热压烧结(HP)技术制备了n型Bi2 Te2.85Se0.15热电材料,在常温下测量了电阻率(ρ)、塞贝克系数(α)和热导率(κ)等热电性能参数,考察了掺杂剂AgI的含量(质量百分比分别为0,0.1,0.2,0.3和0.4％)对材料热电性能的影响.结果表明:试样的电阻率和塞贝克系数的绝对值均随AgI掺杂量的提高而增大,热导率则随AgI掺杂量的提高而大幅降低,在AgI掺杂量为0.2％(质量)时有最大热电优值,为2.0×10-3/K.     

四元Mg_2Si_(0.27)Ge_(0.05)Sn_(0.65)Sb_(0.03)固溶体的热电性能（英文）

通过氧化硼助熔剂法和放电等离子烧结技术制备了Mg_(2(1+x))Si_(0.27)Ge_(0.05)Sn_(0.65)Sb_(0.03)(x=0.05,0.08)四元固溶体热电材料。在300~800 K的温度区间内测试了所有四元固溶体试样的塞贝克系数、电导率和热导率。结果表明随着温度的升高电导率单调降低而塞贝克系数单调升高,所有样品的晶格热导率明显高于通过Abeles模型计算所得到的理论值。最高无量纲热电优值ZT出现在x=0.08样品中,在800 K时达到最高值1.0。     

Sb掺杂Mg2-xZnxSi固溶体的热电性能

利用B2O3助熔剂法结合SPS技术制备了Mg2-xZnxSi0.99Sb0.01(0 ≤ x ≤ 0.1)固溶体。测量了300 K - 780 K温度区间内试样的电导率、塞贝克系数和热导率。发现晶格热导率随Zn取代量的增大而降低。而电导率随Zn取代量的增大而先降低后增大。讨论了影响电导率与晶格热导率的变化规律的具体内在机制。所有样品中x=0.075样品的功率影子最高,在780 K达到1.76 mWm-1K-2,比基体Mg2Si0.99Sb0.01高约18%。x=0.1样品具有最低的晶格热导率,在770 K达到2.86 Wm-1K-1。低晶格热导率使Mg1.9Zn0.1Si0.99Sb0.01具有最高热电优值,在780 K达到0.37。     

四元Mg2Si0.27Ge0.05Sn0.65Sb0.03固溶体的热电性能

通过氧化硼助熔剂法和放电等离子烧结技术制备了Mg_2(1+x)Si_0.27Ge_0.05Sn_0.65Sb_0.03 (x = 0.05, 0.08)四元固溶体热电材料。测量了在300 K - 800 K 的温度区间内测试了所有四元固溶体试样的塞贝克系数、电导率和热导率。研究结果表明随着温度的升高电导率单调降低而塞贝克系数单调升高,所有样品的晶格热导率明显高于通过Abeles模型计算所得到的理论值。最高无量纲热电优值出现在x=0.08样品中,在800 K时达到最高值1.0.     

额外Te的掺杂量对P型碲化铋基合金热电性能的影响

采用区熔法制备了P型（Bi0.15Sb0.85）2Te3＋x％Te（z=0-6）热电材料，利用电子探针（EPMA）观察了区熔材料的显微结构并进行了物相分析，在300～500K的温度范围内分别测量了材料的塞贝克系数α、电导率σ以及热导率κ。结果表明：随着额外Te的含量增加，材料的载流子（空穴）浓度减小，电导率降低；同时，载流子对声子的散射作用减弱，但第二相的存在对声子的散射作用增强，二者的共同作用使晶格热导率在室温附近随着Te含量先减小而后增大。材料的性能优值ZT则随Te含量先增大后减小，当额外Te的质量分数为3％时具有最大的ZT值，约为0．92。     

Mg_2Si同质纳微米复合材料的制备及其热电性能

以平均晶粒尺寸约3μm及20 nm的Mg_2Si粉末为原料,采用放电等离子体烧结方法制备出不同纳米、微米含量的Mg_2Si纳微米复合块体材料,系统研究了纳微米结构对材料热电性能的影响.结果表明:随复合材料中纳米颗粒含量的增加,晶界散射增强,导致材料晶格热导率κ_p有明显降低;同时晶界势垒散射的增强也导致Seebeck系数α显著增加,电导率σ有一定程度的降低;综合Seebeck系数α、电导率σ、热导率κ的影响,在纳米颗粒含量为50%(质量分数,下同)、823 K时,获得最大热电优值达0.45,分别是未掺杂纳米相和完全纳米相Mg_2Si材料的1.5及1.1倍.纳微米复合结构的引入,可以获得性能更好的Mg_2Si热电材料.     

Cu_(y)Bi_(2)Te_(2.62)S_(0.08)Se_(0.3)热电材料的微观结构与热电性能EI北大核心CSCD

采用合金设计、真空熔炼、快速凝固、球磨制粉、冷压成形和常压烧结工艺,制备了Cu、S掺杂的n型Bi_(2)Te_(2.7)Se_(0.3)热电材料,采用XRD、SEM和ZEM-3热电测试系统等表征热电材料晶体结构、微观形貌和热电性能,研究Cu、S掺杂的n型Bi_(2)Te_(2.7)Se_(0.3)热电材料热电性能机理。结果表明:Cu_(y)Bi_(2)Te_(2.62)S_(0.08)Se_(0.3)热电材料晶体结构为R-3m空间群斜方晶系的六面体层状结构;掺杂Cu的Cu_(y)Bi_(2)Te_(2.7)Se_(0.3)热电材料,形成Cui间隙缺陷和Bi′Te反位缺陷,随着载流子(电子)浓度增加,载流子迁移率降低,电导率显著增大;掺杂S的Bi_(2)Te_(2.62-z)SzSe_(0.3)热电材料,生成化学键健能较Bi-Te强的Bi-S,抑制反位缺陷Bi′Te形成,少数(空穴)载流子浓度减小,同时增强声子对声子散射和点缺陷对声子散射,从而使晶格热导率和双极扩散热导率降低,总热导率明显降低,抑制塞贝克系数的减少;Cu、S共掺杂的协同作用,n型Cu_(y)Bi_(2)Te_(2.62-z)SzSe_(0.3)热电材料电导率增大,而热导率基本不变,由此ZT值和功率因子显著提高;在300~400 K温度范围内,Cu_(0.03)Bi_(2)Te_(2.62)S_(0.08)Se_(0.3)的电导率约为7.0×10^(4)S/m,塞贝克系数约为220μV/K,功率因子约为2.4 m W/(m·K^(2)),热电优值(ZT值)约为1.0。Cu_(0.03)Bi_(2)Te_(2.62)S_(0.08)Se_(0.3)热电材料可广泛应用于低温尤其室温条件下的热电制冷器件和温差发电电池。     

Sb掺杂Mg_(2-x)Zn_xSi(0≤x≤0.1)固溶体的热电性能（英文）

利用B_2O_3助熔剂法结合SPS技术制备了Mg_(2-x)Zn_xSi_(0.99)Sb_(0.01)(0≤x≤0.1)固溶体。测量了300~780 K温度区间内试样的电导率、塞贝克系数和热导率。发现晶格热导率随Zn取代量的增大而降低。而电导率随Zn取代量的增大而先降低后增大。讨论了影响电导率与晶格热导率的变化规律的具体内在机制。所有样品中x=0.075样品的功率因子最高,在780 K达1.76 m W·m~(-1)·K~(-2),比基体Mg_(2-x)Zn_xSi_(0.99)Sb_(0.01)高约18%。x=0.1样品具有最低晶格热导率,在770 K达到2.86 W·m~(-1)·K~(-1)。低晶格热导率使Mg_(1.9)Zn_(0.1)Si_(0.99)Sb_(0.01)具有最高热电优值,在780 K达0.37。     

GaSb添加和Sb掺杂对Mg2Si0.5Sn0.5固溶体热电性能的影响（英文）

利用B2O3助熔剂法结合热压法制备了Mg2Si0.487-2x Sn0.5(Ga Sb)x Sb0.013(0.04≤x≤0.10)固溶体。X射线衍射结果表明样品呈单相。Sb掺杂有效提高了样品的电导率。随温度升高,Mg2Si0.487-2x Sn0.5(Ga Sb)x Sb0.013(0.04≤x≤0.10)样品的电导率降低而塞贝克系数升高。随Ga Sb含量的增多,样品的电导率呈现出先增大后减小的变化趋势。所有样品中Mg2Si0.287Sn0.5(Ga Sb)0.1Sb0.013具有最低晶格热导率,其室温晶格热导率比Mg2Si0.5Sn0.5[11]低15%。由于电导率较高使Mg2Si0.327Sn0.5(Ga Sb)0.08Sb0.013具有最高热电优值,在720 K达到0.61,显著高于基体Mg2Si0.5Sn0.5[11]的最高热电优值0.019。     

GaSb添加和Sb掺杂对Mg_2Si_(0.5)Sn_(0.5)固溶体热电性能的影响(英文)

利用B2O3助熔剂法结合热压法制备了Mg2Si0.487-2x Sn0.5(Ga Sb)x Sb0.013(0.04≤x≤0.10)固溶体。X射线衍射结果表明样品呈单相。Sb掺杂有效提高了样品的电导率。随温度升高,Mg2Si0.487-2x Sn0.5(Ga Sb)x Sb0.013(0.04≤x≤0.10)样品的电导率降低而塞贝克系数升高。随Ga Sb含量的增多,样品的电导率呈现出先增大后减小的变化趋势。所有样品中Mg2Si0.287Sn0.5(Ga Sb)0.1Sb0.013具有最低晶格热导率,其室温晶格热导率比Mg2Si0.5Sn0.5[11]低15%。由于电导率较高使Mg2Si0.327Sn0.5(Ga Sb)0.08Sb0.013具有最高热电优值,在720 K达到0.61,显著高于基体Mg2Si0.5Sn0.5[11]的最高热电优值0.019。     

Sb掺杂对Mg_2Si基化合物热电性能的影响(英文)

采用感应熔炼和真空热压的方法制备了Sb掺杂和未掺杂的Mg2Si基热电材料.研究了Sb掺杂对Mg2Si基热电材料的结构以及热电特性的影响.结果表明:通过Sb掺杂使得载流子浓度从3.07x1019 cm-3增加到1.25x1020 cm-3,电子有效质量也相应增加.测试了从室温到800 K下试样的Seebeck系数,电导率和热导率.结果显示,0.3 at%Sb掺杂使得电导率得到显著增加,在783 K时,ZT值达到0.7.     

Mg2Si的微波固相合成及其热电性能

为了解决Mg2Si传统制备方法中Mg的氧化、挥发等问题,采用微波低温固相反应法合成Mg2Si热电材料。用XRD分析手段研究合成产物的结构及相组成。在300到700K的温度范围内,对材料的电导率、Seebeck系数和热导率随温度的变化进行测量。结果表明,当Mg过量8%、加热功率为2.5kW时,于853K保温30min,可以得到单相Mg2Si热电化合物。在测试温度范围内,Mg2Si具有较高的品质因数ZT值,在600K温度下达到0.13。     

电场激活合成Mg2Si的热电性能研究

用Mg粉和Si粉通过电场激活加压辅助法（Field-activated and Pressure-assisted Synthesis,FAPAS）,在1073 K、50 MPa条件下快速实现了Mg2Si块体热电材料的一步法合成与致密化;合成过程反应物反应完全,产物的XRD曲线的Mg2Si峰型尖锐,占产物含量的99.5%。合成样品的Seebeck系数、电导率、功率因子分别在562K、773 K、600 K时达到最大值,分别为445μVK-1、54.4 Scm^-1、4.35 W/cmK^2。通过对比多种方法合成的Mg2Si热电材料的热电性能发现,FAPASA样品的功率因子比其它方法具有明显的优势。     

Thermoelectric figure-of-merit of iodine-doped copolymer of phenylenevinylene with dialkoxyphenylenevinylene

The copolymers consisting of both unsubstituted and 2,5-dialkoxy-substituted phenylenevinylenes (P(ROPV-co-PV); RO = MeO, EtO and BuO) with ca. 30 mol% of dialkoxy-substituted units were synthesized to evaluate their thermoelectric properties. Iodine-doped P(ROPV-co-PV) exhibited high Seebeck coefficient with relatively high electrical conductivity among electrically conductive polymers ever reported. The effect of the stretching treatment on their thermoelectric properties was examined. Consequently, both P(MeOPV-co-PV) and P(EtOPV-co-PV) constantly showed high Seebeck coefficients with increased electrical conductivities by the stretching alignment because of an increase in the carrier mobility, while the Seebeck coefficient of P(BuOPV-co-PV) varied inversely with a variation of the electrical conductivity. We also evaluated thermal conductivity of the pristine and iodine-doped P(ROPV-co-PV) for calculations of their thermoelectric figure-of-merit ZT. To the best of our knowledge, consequent thermoelectric figure-of-merit ZT of all the iodine-doped copolymer with the stretch treatment is one of the highest thermoelectric performance among conducting polymers reported ever, which are comparable with that of an inorganic thermoelectric materials, such as β-FeSi₂.     

A three-in-one improvement in thermoelectric properties of polyaniline brought by nanostructures

β-Naphthalene sulfonic acid doped polyaniline nanotubes (PANI NT) was synthesized, a sample without specific nanostructure was prepared as a reference. Seebeck coefficient, electrical and thermal conductivity of both samples were studied. For a PANI NT prepared with an aniline/NSA ratio of 4:1, the Seebeck coefficient had a value of 212.4 μV/K at 300 K, which was 7 times higher than that of the reference sample. Meanwhile, electrical conductivity almost doubled, changed from 0.0045 to 0.0077 S/cm, while the thermal conductivity reduced by 27.5%, dropped from 0.29 to 0.21 W/m K. Finally, thermoelectric performance was evaluated by calculating the thermoelectric power factor and figure of merit, and there was a two orders of magnitude's increase for the tube-like PANI. A series of PANI NTs prepared under different aniline/NSA ratio were also investigated for searching an optimized performance. Tubular nanostructure was proved to be effective for enhancing the thermoelectric performance. This idea might be applicable to other organic thermoelectric materials as well.     

Thermoelectric properties of Ni- and Zn-doped Nd2CuO4

The electrical resistivity, Seebeck coefficient, and thermal conductivity of Nd₂(Cu_0.98M_0.02)O₄ (M: Ni and Zn) have been measured in the temperature range from room temperature to about 1000 K. Ni- and Zn-doping decreases the electrical resistivity and the absolute values of the Seebeck coefficient. The thermal conductivity decreases with increasing temperature, showing phonon conduction, and also decreases by doping. The power factor of Nd₂(Cu_0.98Ni_0.02)O₄ reaches 1.02×10⁻⁴ W m⁻¹ K⁻² and the figure of merit is 1.35×10⁻⁵ K⁻¹ at 320 K. The relatively low figure of merit compared with that of the state-of-the-art thermoelectric materials is due to the high thermal conductivity.     

锗相的存在对Sr_8Ga_(16)Ge_(30)clathrates结构热电材料性能的影响

无机clathrate结构化合物是非常有前景的热电材料.在镓取代的锗基clathrate结构热电材料的合成中,普遍存在锗的第二相.本研究合成了多晶Sr_8Ga_(16)Ge_(30) clathrates 结构热电材料.用X射线衍射结合样品抛光表面的背散射电子像对样品中锗相的含量进行表征.测试可知,材料表现为n型半导体,随着Ge相含量的增大,Seebeck系数绝对值增大,电导和热导率减小.功率因子最大为12.8 μW·K~(-2)cm~(-1).Sr_8Ga_(16)Ge_(30)样品在650 K的最大ZT值达到0.65.     

B掺杂p型SiGe合金的制备与热电性能表征

SiGe合金作为一种重要的高温热电材料一直被广泛关注并得到商业应用,其n型SiGe合金热电材料的无量纲热电优值(ZT)取得较大进步,但是p型SiGe合金的ZT值仍然较低。本文,以一定化学计量比均匀混合的Si、Ge、B混合粉末为原材料,使用放电等离子烧结(SPS)系统一步法合金化制备了p型Si80Ge20Bx(x=0.5,1.0,2.0)合金热电材料,并对样品的组成、微观形貌、热电性能进行了表征与分析。结果表明,放电等离子烧结过程实现原位合金化并烧结为块体材料。随着B掺杂量的增加,电导率明显提升,热导率显著下降,当温度为950 K时,热导率为1.79 W /(m?K)。在1050 K时,ZT值达到了0.899。球磨和掺杂的协同作用使得SiGe结构基体中产生不同类型的缺陷特征而散射不同波长的声子,导致硅锗合金热导率的降低。     

Enhanced Seebeck coefficient by energy filtering in Bi-Sb-Te based composites with dispersed Y2O3 nanoparticles

The incorporation of ceramic nanoparticles in the bulk thermoelectric matrix is one of the new strategies to boost the Seebeck coefficient. In this research, different weight percentages of Y₂O₃ (2, 4, and 6) nanoparticles (NPs) were incorporated into the pre-alloyed BiSbTe powder for making nanocomposites (NCs) by mechanical milling. The resultant NCs powders were subsequently consolidation by spark plasma sintering (SPS) at 450 °C. The existence of Y₂O₃ nano-inclusions was confirmed by x-ray diffraction and TEM-SAED analysis. The hardness of the nanocomposites was significantly improved (>49%) compared to that of pure BiSbTe, and this was attributed to grain-boundary hardening and to a dispersion strengthening mechanism. The electrical conductivity decreased while the Seebeck coefficient significantly improved (45%) at room temperature for the NCs to which 2 wt% Y₂O₃ was added. This was due to the scattering of carriers through the energy filtering effect. The electronic component of the thermal conductivity greatly contributed to the reduction of total thermal conductivity (22%) in BiSbTe NCs to which 6 wt% Y₂O₃ was added. A peak ZT of 1.24 was achieved for BiSbTe/(2 wt%) Y₂O₃ NCs due to reduction in their thermal conductivity and improved Seebeck coefficient values.