Ca3Co4O9陶瓷的结构与性能

采用传统固相烧结法制备了Ca3Co4O9陶瓷,并对其显微结构和热电性能进行了研究。实验结果表明,Ca3Co4O9为六角形层状结构,晶胞参数a=5.0,c=10.7,属P型半导体,Seebeck系数和电导率均随着温度的升高而增大。     

掺杂金属离子对Ca3Co4O9的热电性能的影响

采用溶胶-凝胶法,在常压空气中,经850℃烧结4h制备了Ca3Co4O9掺杂不同金属离子M(Na ,Ag ,La2 )的(Ca1-xMx)3Co4O9热电材料.通过X射线衍射、扫描电镜等对材料的微结构进行了表征,重点考察了掺杂不同金属离子对Ca3Co4O9中温热电性能参数Seebeck系数、电导率和功率因子的影响.结果表明:金属掺杂的(Ca1-xMx)3Co4O9热电材料具有致密的内部结构,并能够明显改善Ca3Co4O9的热电性能,尤其是掺杂Na 样品的热电性能有较为明显的提高,并且掺杂离子浓度对改善热电性能也有一定影响,组成为(Ca0.90Na0.10)3Co4O9时的功率因子提高最明显.     

Ca_(2.7)Sr_(0.3)Co_4O_9 和 Ca_(0.95)Sm_(0.05)MnO_3 热电材料的性能及器件(英文)

为了构造具有一定实用性能的氧化物热电器件,对 p 型 Ca3Co4O9和 n 型 CaMnO3过渡金属氧化物半导体进行研究,结果表明:Ca2.7Sr0.3Co4O9和 Ca0.95Sm0.05MnO3的热电性能良好。Ca2.7Sr0.3Co4O9陶瓷的微观形貌呈片层状及尖锐的(00?)相,说明具有高度织构,Ca0.95Sm0.05MnO3陶瓷为单一相正交晶系。分析了样品形成的化学反应过程。热电参数测试结果表明:Ca2.7Sr0.3Co4O9为 p 型半导体,空穴导电机制,Ca0.95Sm0.05MnO3为 n 型半导体,电子导电机制。两种材料的电阻均较低,在 870 K,Seebeck 系数分别为 170 μV/K 和–167 μV/K。在测量温度范围内,热导率变化很小,并计算出热电优值。利用此两种材料构造热电器件,并对其性能进行测试。     

掺纳对钴酸钙热电性能影响研究

采用溶胶-凝胶法制备了掺Na的Ca3Co4O9热电材料,研究了Na掺量对试样物相、电导率、Seebeck系数和功率因子的影响。研究发现随着Na掺量增加,试样中Ca3Co4O9的含量下降,但试样的电导率增加。Na掺量为0．10的试样,在973K时的功率因子最大,为3．8×10-4w／m·K^2。     

掺钠对钴酸钙热电性能影响研究

采用溶胶-凝胶法制备了掺Na的Ca3Co4O9热电材料,研究了Na掺量对试样物相、电导率、Seebeck系数和功率因子的影响。研究发现随着Na掺量增加,试样中Ca3Co4O9的含量下降,但试样的电导率增加。Na掺量为0.10的试样,在973K时的功率因子最大,为3.8×10-4W/m.K2。     

不同粉体制备工艺对Ca3Co4O9陶瓷性能的影响

采用溶胶凝胶法和化学共沉淀法制备了Ca3Co4O9粉体,并烧结为纯相Ca3Co4O9陶瓷。利用XRD、SEM等方法对陶瓷样品的物相以及断面形貌进行了表征,利用四探针法测量了Ca3Co4O9陶瓷的电导率。试验结果表明化学共沉淀法与溶胶凝胶法粉体相比,制得的Ca3Co4O9陶瓷不仅具有更低的气孔率、线收缩率,而且具有更高的电导率,也是一种制备高性能热电材料粉体的有效方法。     

氟掺杂对Ca3Co4O9化合物微观结构和热电性能的影响

采用固相合成法及放电等离子烧结制备了Ca3Co4(FxO1-x)9(x=0,0.01,0.02)块体样品,系统研究了氟(F)掺杂对Ca3Co4O9微观结构和热电性能的影响。结果表明:F掺杂样品均为单一化合物。在300～900K,与纯样相比,F掺杂样品的Seebeck系数变化较小,电导率显著增大,热导率先减小后随F掺量的增加而增大。x=0.01时,样品具有最高电导率和最低热导率,分别为14×103S/m和2.16W/(m·K)。在900K,样品最大热电优值(ZT值)为0.16,较纯样品的提高了近100%。     

高分子热电材料研究进展

由于无机热电材料的资源有限、价格昂贵、加工复杂,价廉易加工的有机热电材料已经引起众多研究者的关注。综述了近几年国内外高分子热电材料领域通过综合利用无机材料的高电导率、高Seebeck系数和有机材料的低热导率制备热电值较高的热电材料的进展。但是高分子热电材料的热电性能相比无机材料还有差距,如何独立、高效地调控Seebeck系数、电导率和热导率,使高分子材料的热电性能提高到和无机热电材料媲美的程度,仍是高分子热电材料领域的巨大挑战。     

制备工艺对La改性的Ca3Co4O9基陶瓷热电性能的影响

利用常压烧结、冷等静压成型后常压烧结及热等静压烧结3种不同制备工艺,合成了(Ca0.9La0.1)3Co4O9热电材料。XRD分析表明：不同工艺制备的样品均为Ca3Co4O9相。样品的SEM照片显示：晶粒为片状结构;热等静压烧结制备的样品,其片状结构不明显,但致密度较之另外两种工艺大幅度提高,其相对密度为95％。制备工艺对(Ca0.9La0.1)3Co4O9热电材料Seebeck系数影响不大,但热压烧结样品能大幅度提高(Ca0.9La0.1)3Co4O9电导率。在一定温度范围内,随温度升高,功率因子大幅度增加,对于热压烧结的样品尤为显著。     

微波加热法制备Ca3-xLaxCo4O9热电材料

采用微波加热法合成了稀土La掺杂的Ca3-xLaxCo4O9材料的前驱粉末,进一步制备了热电材料烧结体.通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)等对材料的微观结构进行了研究,通过电导率的测量、Seebeck系数以及热导率的计算研究了材料的热电性能.实验结果表明,微波加热法可以在较短的时间内制得Ca3-xLaxCo4O9粉体,微波烧结方法时间短,效率高,并且晶粒生长完善且晶粒细小.Ca3-xLCo4O9热电材料的微观结构为片状结构,晶粒生长完整.     

Ca3Co4O9热电陶瓷材料的制备与表征

本实验采用溶胶-凝胶法制备了Ca3Co4O9陶瓷,对样品的显微结构和热电性能进行了表征.实验结果表明,Ca3Co4O9为取向无规则层片状组织,制备工艺参数对样品的显微结构和热电性能有重要影响.     

Synthesis and thermoelectric properties of (NaxCa1−x)3Co4O9 ceramics

(Na_xCa_1−x)₃Co₄O₉ (x=0.05−0.2) ceramics with a layered crystal structure were prepared by a sol–gel method followed by a low-temperature sintering procedure. The electrical conductivity and Seebeck coefficient of the complex oxide ceramics were measured from 400 to 900 °C. Their electrical conductivity and power factor increase with increasing temperature, while the thermal conductivity is very weakly dependant on the temperature. Na dopant amount has a remarkable effect on electrical and thermal transport properties. The figure of merit in the ceramic samples is smaller than that of traditional thermoelectric alloys.     

Thermoelectric Properties of Pb‐Doped BiCuSeO Ceramics

A high‐performance thermoelectric BiCuSeO oxyselenides has been prepared by a simple fabrication approach. Phase composition and microstructure analysis indicate that the obtained ceramic samples are almost BiCuSeO phase with plate structure. Our results show that Pb‐doped BiCuSeO bulks have good electrical conductivity, large Seebeck coefficient, and low thermal conductivity. A large power factor ~672 μ/Wm/K² at 573 K can be observed in the BiCuSeO ceramic by the 10% Pb doping, and the dimensionless figure of merit (ZT) can reach 0.95 at 873 K, which makes them promising candidates for thermoelectric applications.     

Sr掺杂对Ca3Co4O9热电性能的影响与理论分析

通过实验研究了Ca位掺杂对Ca3CoaO9热电性能的影响，并用密度泛函离散变分法从理论和计算上寻求支持，从化学键角度对此现象进行解释。结果发现：与未掺杂体系相比较，x=0．05有利于降低材料的电阻率，但Seebeck系数有所减弱；z=0．10对降低电阻率不利；体系在473～773K范围内具有hopping电导的特征。建...     

Self-templated synthesis and thermal conductivity investigation for ultrathin perovskite oxide nanowires

The large thermal conductivity of bulk complex metal oxides such as SrTiO(3), NaCo(2)O(4), and Ca(3)Co(4)O(9) has set a barrier for the improvement of thermoelectric figure of merit and the applications of these materials in high temperature (≥1000 K) thermoelectric energy harvesting and solid-state cooling. Here, we present a self-templated synthesis approach to grow ultrathin SrTiO(3) nanowires with an average diameter of 6 nm in large quantity. The thermal conductivity of the bulk pellet made by compressing nanowire powder using spark plasma sintering shows a 64% reduction in thermal conductivity at 1000 K, which agrees well with theoretical modeling.     

High-Temperature Electrical Transport Behavior Observed in the La1.96M0.04CuO4 (M: Mg, Ca, Sr) Polycrystalline Ceramics

We prepared high-density La_1.96M_0.04CuO₄ (M: Mg, Ca, Sr) polycrystalline ceramics by a spark plasma sintering method, and investigated the temperature dependence of the electrical conductivity, Seebeck coefficient, and power factor. Our results indicate that the relative density of these sintered ceramic samples can reach nearly 100%, and alkaline earth metal ions doping can increase the activation energy (from 0.021 to 0.128 eV). All ceramic samples show high positive Seebeck coefficient (∼100–510 μV/K). The obtained Sr-doped La₂CuO₄ ceramics show better thermoelectric properties, which potentially make them for thermoelectric applications.