首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 281 毫秒
1.
王志国  向俊尤  徐宝  万素磊  鲁毅  张雪峰  赵建军 《物理学报》2015,64(6):67501-067501
采用传统的高温固相烧结法制备了双层钙钛矿锰氧化物(La1-xGdx)4/3Sr5/3Mn2 O7 (x=0, 0.025)多晶样品. 通过X射线衍射仪研究发现样品为Sr3Ti2O7型四方结构, 空间群为I4/mmm; 磁性测量表明, Gd3+掺杂后的样品(La0.975Gd0.025)4/3Sr5/3Mn2O7的三维磁有序转变温度(TC13D)、磁化强度(M)均降低, 这是由于Gd3+的掺杂引起晶格的畸变, 从而使得晶格常数发生改变, 减弱了铁磁耦合而导致的; 通过电子自旋共振谱测量发现, 在TC3D<T<300 K温度范围内, 两样品在顺磁的基体上均有短程的铁磁团簇存在, 出现了相分离现象. 电性测量表明: 两样品分别在TC13D (La4/3Sr5/3Mn2O7 样品的三维磁有序转变温度, TC03D)<T<300 K温度范围内均以三维变程跳跃的方式导电, 分析得出Gd3+的掺杂使得载流子局域长度的减小. 这表明载流子需要吸收更多的能量才能克服晶格的束缚进行跳跃, 因此(La0.975Gd0.025)4/3Sr5/3Mn2 O7 样品的电阻较高.  相似文献   

2.
用固相反应法制备了Ba1-xSrxTiO3(BST)及Ba0.6-xPbxSr0.4TiO3(BPST)陶瓷,通过XRD,FESEM和拉曼谱分析了Pb掺杂对Ba0.6Sr0.4TiO3样品的晶格、相变及表面形貌的影响.测试了BST及B 关键词: BST BPST 弥散相 介温特性  相似文献   

3.
用固相反应方法,成功地合成了具有交互生长结构的LixNayCoO2单相多晶系列样品. 热电势测量表明,该系统的室温热电势比NaxCoO2体系约高出60μV/K. 基于空穴载流子具有O2p特征,提出LixNayCoO2中额外的热电势来源于氧空穴的占位熵. 关键词xNayCoO2')" href="#">LixNayCoO2 热电势 热电材料  相似文献   

4.
刘胜利  厉建峥  程杰  王海云  李永涛  张红光  李兴鳌 《物理学报》2015,64(20):207103-207103
利用固相反应法成功制备了Sr2-xLaxIrO4系列掺杂样品, 并详细研究了样品晶体结构随掺杂的演变. 拉曼散射峰向高频移动和X射线衍射谱的结构精修数据发现随着掺杂量的增加, c轴晶格常数减小, 顶角Ir–O1键键长随之减小, 表明掺杂导致晶格收缩, 而且IrO6八面体畸变程度减弱. 变温拉曼散射谱显示随着温度降低也出现蓝移现象, 且与顶角氧相关的拉曼振动模式的蓝移在110 K附近出现明显跳变, 表明在该温度附近出现了结构变化和磁性质转变.  相似文献   

5.
王强 《物理学报》2010,59(9):6569-6574
利用固相反应法制备了Bi0.5Ca0.5Mn1-xCoxO3(0≤x≤0.12)系列多晶样品.研究了Co掺杂对Bi0.5Ca0.5MnO3电荷有序的影响.结果表明,Co掺杂导致电荷有序相逐渐融化、铁磁相互作用的增强;当x≥0.08时,电荷有序转变峰完全消失,但残留的反铁磁电荷有 关键词: 钙钛矿锰氧化物 电荷有序 团簇玻璃 相分离  相似文献   

6.
利用固相反应烧结技术制备La0.1Bi0.9-xEuxFeO3系列化合物. 利用X射线粉末衍射进行物相鉴定和结构分析,确定了材料的相关系:x≤0.05,材料为R3c结构相;0.08≤x≤0.12,材料为赝R3c结构相;x≥0.15是Pbnm相,其中0.15≤x≤0.20区域Pbnm相存在畸变. 磁测量结果表明,材料具有弱铁磁性,对于x≤0.20材料,磁矩在x=0.12成分存在极值. 利用阻抗分析仪测量了室温介电常数随成分的变化关系.讨论了材料的结构与弱铁磁性和室温介电常数间的关系. 关键词: 0.1Bi0.9-xEuxFeO3')" href="#">La0.1Bi0.9-xEuxFeO3 X射线衍射 磁性 介电常数  相似文献   

7.
李健  宋功保  王美丽  张宝述 《物理学报》2007,56(6):3379-3387
采用溶胶凝胶法制备了Ti1-xCrxOδ体系系列样品.利用扫描电子显微镜(SEM),X射线光电子能谱(XPS),粉末X射线衍射分析(XRD)方法研究了Ti1-xCrxOδ系列样品的颗粒尺寸、形貌、组分化学态、相关系和固溶区范围;并利用超导量子干涉磁强计对样品的磁性能进行了研究.采用Rietveld结构精修的方法研究了Cr的不同掺杂量对TiO2晶体结构的影响,研究表明,1000℃烧结的样品的固溶区范围是x=0—0.03,为金红石单相;随着Cr掺杂量的增加,金红石相晶胞参数规律性地减小;当x>0.03,为金红石相和CrO2相两相共存.综合XRD和磁性测量结果,500℃烧结的样品的固溶区范围是x=0—0.02,为锐钛矿单相;随着Cr掺杂量的增加,锐钛矿相晶胞参数规律性地减小;当x≥0.04,为锐钛矿相和绿铬矿相(Cr2O3)两相共存.XPS实验结果表明,500℃和1000℃退火的样品中Cr都是以Cr+3和Cr+6两种化学态存在,1000℃烧结的样品中可能有更多的Cr3+转化为Cr6+.根据M-HM-T曲线的测试结果发现,本文500℃烧结的Ti1-xCrxOδ体系样品当x=0—0.02时,为室温铁磁性.当x≥0.04时,由铁磁相和顺磁相所组成,在低温下有较强的铁磁性;室温下主要是顺磁相,铁磁相只占据很小的体积分数. 关键词: 1-xCrxOδ体系')" href="#">Ti1-xCrxOδ体系 相关系 固溶区 磁性能  相似文献   

8.
王作成  李涵  苏贤礼  唐新峰 《物理学报》2011,60(2):27202-027202
用熔融退火结合放电等离子烧结法制备了In0.3Co4Sb12-xSex(x=0—0.3)方钴矿热电材料,探讨了In的存在形式,系统研究了Se掺杂量对结构和热电性能的影响.结果表明:In可以填充到方钴矿二十面体空洞处,过量In在晶界处形成InSb第二相,Se对Sb的置换使晶格常数减小,In填充上限降低;In0.3Co4Sb12-xSex样品呈n型传导,随着Se掺杂量的增大,载流子浓度降低,电导率下降,Seebeck系数增大,功率因子有所降低;由于在结构中引入了质量波动及晶格畸变,适量的Se掺杂可以大幅降低材料晶格热导率;样品In0.3Co4Sb12和In0.3Co4Sb11.95Se0.05的最大ZT值均达到1.0以上. 关键词: 掺杂 填充式方钴矿 热电性能  相似文献   

9.
刘明  曹世勋  袁淑娟  康保娟  鲁波  张金仓 《物理学报》2013,62(14):147601-147601
利用固相反应法制备了Dy1-xPrxFeO3系列化合物. X射线粉末衍射晶体结构分析表明, 随着Pr掺杂量x的增加, 样品晶胞体积逐渐增大, 晶格畸变减弱. Raman光谱测量表明稀土离子有效质量[meff=xmPr+(1-x)mDy] 与晶格结构的变化共同导致该体系Raman光谱的变化. 随Pr掺杂量的增加, 波数小于200 cm-1的振动模式基本保持不变, 而波数大于200 cm-1的振动模式(除420 cm-1处的B3u模式外)向低频移动. 磁测量结果表明, 由Dzyaloshinsky-Moriya 相互作用导致的宏观磁性随Pr掺杂量增加逐渐减弱. 稀土离子与铁离子磁晶格的耦合作用以及晶格结构畸变的变化共同导致该体系自旋重取向相变温度在一定的掺杂量 (x=0.3)前后先升高后降低. 关键词: 稀土铁氧体 自旋重取向 晶体结构 Raman光谱  相似文献   

10.
史力斌  李容兵  成爽  李明标 《物理学报》2009,58(9):6446-6452
采用基于密度泛函理论和平面波赝势技术的CASTEP程序对Zn1-xBexO合金电子结构和光学性质进行了计算.当0≤x≤1,其带隙从0.963 eV变化到7.293 eV.分析了晶格畸变和能带间排斥效应对带隙的影响.当Be含量x=0.125,0.25,0.375,0.5,0.625,0.75时,a/b轴压应变控制着带隙变化;当x=0.875,1时,c轴压应变控制着带隙变化.能带间的p-d排斥影响价带顶变动,Γ1vΓ1c之间排斥影响导带底变动.这些能带间的排斥效应被用来分析Zn1-xBexO带隙变动.另外,也分析了Zn1-xBexO介电函数虚部ε2. 关键词: 带结构 光学性质 应变 排斥  相似文献   

11.
刘冉  高琳洁  李龙江  翟胜军  王江龙  傅广生  王淑芳 《物理学报》2015,64(21):218101-218101
以CaCO3作为Ca2+源, 利用传统固相烧结法制备了Cd1-xCaxO (x=0, 0.01, 0.03, 0.05) 多晶块体样品并研究了Ca2+掺杂对CdO高温热电性能的影响. CaCO3的掺入会导致CdO多晶载流子浓度降低, 使Cd1-xCaxO的电阻率ρ和塞贝克系数的绝对值|S|增大、电子热导率κe减小. 同时, 在CdO中掺入CaCO3会引入点缺陷和气孔并可抑制CdO晶粒长大、晶界增多, 从而增加了对声子的散射, 使样品的声子热导率κp减小. 由于总热导率的大幅降低, Cd0.99Ca0.01O多晶样品在1000 K时的热电优值ZT可达0.42, 比本征CdO提高了约27%, 为迄今n型氧化物热电材料报道的最好结果之一.  相似文献   

12.
High-performance organic composite thermoelectric(TE)materials are considered as a promising alternative for harvesting heat energy.Herein,composite films of poly(3,4-ethyienedioxythiophene):poly(styrene sulfonate)/single-walled carbon nanotubes(PEDOT:PSS/SWCNTs)were fabricated by utilizing a convenient solution mixing method.Thereafter,the as-prepared hybrid films were treated using sulfuric acid(H2SO4)to further optimize the TE performance.Film morphological studies revealed that the sulfuric acid treated PEDOT:PSS/SWCNTs composite samples all possessed porous structures.Due to the successful fabrication of highly conductive networks,the porous nano-architecture also exhibited much more excellent TE properties when compared with the dense structure of the pristine samples.For the post-treated sample,a high power factor of 156.43μW·m-1·K-2can be achieved by adjusting the content of CNTs,which is approximately 3 orders of magnitude higher than that of the corresponding untreated samples(0.23μW·m-1·K-2).Besides,the obtained films also showed excellent mechanical flexibility,owing to the porous nanostructure and the strong p–p interactions between the two components.This work indicates that the H2SO4 treatment could be a promising strategy for fabricating highly-flexible and porous PEDOT:PSS/SWCNTs films with high TE performances.  相似文献   

13.
《中国物理 B》2021,30(9):97204-097204
Strontium titanate(SrTiO_3) is a thermoelectric material with large Seebeck coefficient that has potential applications in high-temperature power generators.To simultaneously achieve a low thermal conductivity and high electrical conductivity,polycrystalline SrTiO_3 with a multi-scale architecture was designed by the co-doping with lanthanum,cerium,and niobium.High-quality nano-powders were synthesized via a hydrothermal method.Nano-inclusions and a nano/microsized second phase precipitated during sintering to form mosaic crystal-like and epitaxial-like structures,which decreased the thermal conductivity.Substituting trivalent Ce and/or La with divalent Sr and substituting pentavalent Nb with tetravalent Ti enhanced the electrical conductivity without decreasing the Seebeck coefficient.By optimizing the dopant type and ratio,a low thermal conductivity of 2.77 W·m~(-1)·K~(-1) and high PF of 1.1 mW·m~(-1)·K~(-2) at 1000 K were obtained in the sample co-doped with 5-mol% La,5-mol% Ce,and 5-mol% Nb,which induced a large ZT of 0.38 at 1000 K.  相似文献   

14.
吴宇  蔡绍洪  邓明森  孙光宇  刘文江  岑超 《物理学报》2017,66(11):116501-116501
高分子导热材料的有效调控受到了日益广泛的关注.应用密度泛函理论(DFT)、中央插入延展(central insertion scheme,CIS)方法及非平衡格林函数(NEGF)理论,对包含432个原子、长18.533 nm的聚乙烯单链量子热输运的同位素效应进行了研究.计算结果表明,室温下长100 nm的纯12C聚乙烯单链的热导率理论上限高达314.1 W·m~(-1)·K~(-1);对于~(12)C聚乙烯单链,其他条件一定时,~(14)C掺杂引起的热导同位素效应比~(13)C更为显著;室温下纯~(12)C聚乙烯单链中~(14)C掺杂原子百分数为50%时同位素效应最显著,此时平均热导比未掺杂时下降了51%.这对探索聚乙烯材料热输运的同位素影响机理具有十分积极的意义.  相似文献   

15.
Nan Lu 《中国物理 B》2022,31(4):47201-047201
We study the thermal and electronic transport properties as well as the thermoelectric (TE) performance of three two-dimensional (2D) XI2 (X=Ge, Sn, Pb) bilayers using density functional theory and Boltzmann transport theory. We compared the lattice thermal conductivity, electrical conductivity, Seebeck coefficient, and dimensionless figure of merit (ZT) for the XI2 monolayers and bilayers. Our results show that the lattice thermal conductivity at room temperature for the bilayers is as low as ~1.1 W·m-1·K-1-1.7 W·m-1·K-1, which is about 1.6 times as large as the monolayers for all the three materials. Electronic structure calculations show that all the XI2 bilayers are indirect-gap semiconductors with the band gap values between 1.84 eV and 1.96 eV at PBE level, which is similar as the corresponding monolayers. The calculated results of ZT show that the bilayer structures display much less direction-dependent TE efficiency and have much larger n-type ZT values compared with the monolayers. The dramatic difference between the monolayer and bilayer indicates that the inter-layer interaction plays an important role in the TE performance of XI2, which provides the tunability on their TE characteristics.  相似文献   

16.
《中国物理 B》2021,30(6):67101-067101
It is reported that SnSe_2 consisting of the same elements as SnSe, is a new promising thermoelectric material with advantageous layered structure. In this work, the thermoelectric performance of polycrystalline SnSe_2 is improved through introducing SnSe phase and electron doping(Cl doped in Se sites). The anisotropic transport properties of SnSe_2 are investigated. A great reduction of the thermal conductivity is achieved in SnSe_2 through introducing SnSe phase, which mainly results from the strong SnSe_2–SnSe inter-phase scattering. Then the carrier concentration is optimized via Cl doping, leading to a great enhancement of the electrical transport properties, thus an extraordinary power factor of ~5.12 μW·cm~(-1)·K~(-2) is achieved along the direction parallel to the spark plasma sintering(SPS) pressure direction( P). Through the comprehensive consideration on the anisotropic thermoelectric transport properties, an enhanced figure of merit ZT is attained and reaches to ~ 0.6 at 773 K in SnSe_2-2% SnSe after 5% Cl doping along the P direction, which is much higher than ~ 0.13 and ~ 0.09 obtained in SnSe_2-2% SnSe and pristine SnSe_2 samples, respectively.  相似文献   

17.
Zuo Xiao 《中国物理 B》2022,31(2):28103-028103
The reduced graphene oxide/silver selenide nanowire (rGO/Ag2Se NW) composite powders were fabricated via a wet chemical approach, and then flexible rGO/Ag2Se NW composite film was prepared by a facile vacuum filtration method combined with cold-pressing treatment. A highest power factor of 228.88 μW·m-1·K-2 was obtained at 331 K for the cold-pressed rGO/Ag2Se NW composite film with 0.01 wt% rGO. The rGO/Ag2Se NW composite film revealed superior flexibility as the power factor retained 94.62% after bending for 500 times with a bending radius of 4 mm, which might be due to the interwoven network structures of Ag2Se NWs and pliability of rGO as well as nylon membrane. These results demonstrated that the GO/Ag2Se NW composite film has a potential for preparation of flexible thermoelectric devices.  相似文献   

18.
采用CO_(2)激光区熔法制备了Lu_(2)O_(3)∶0.5%Er^(3+)/x%Yb^(3+)(x=1,3,5)上转换荧光材料。X射线衍射结果表明,所制备的Lu_(2)O_(3)∶Er^(3+)/Yb^(3+)荧光材料具有纯Lu_(2)O_(3)晶相。在980 nm激光激发下,样品发出明亮的上转换荧光。光谱测试结果表明,样品上转换荧光强度和荧光中绿光与红光比例随Yb^(3+)离子浓度改变,当Er^(3+)和Yb^(3+)离子浓度分别为0.5%和3%时,样品上转换荧光强度最强。通过荧光强度比(FIR)技术研究了样品Lu_(2)O_(3)∶0.5%Er^(3+)/3%Yb^(3+)在298~873 K温度范围内上转换荧光温度传感特性,在532.8 K时最大绝对灵敏度为0.0060 K^(-1),在298 K时最大相对灵敏度为0.0090 K^(-1)。结果表明,Lu_(2)O_(3)∶Er^(3+)/Yb^(3+)荧光材料非常适合用于宽温度范围荧光温度传感。  相似文献   

19.
王拓  陈弘毅  仇鹏飞  史迅  陈立东 《物理学报》2019,68(9):90201-090201
硫化银(Ag_2S)是一种典型的快离子导体材料,前期关于Ag_2S的研究主要集中在光电和生物等领域.最近的研究表明, a-Ag_2S具有和金属一样的良好延展性和变形能力.但是, Ag_2S的热电性能尚无公开报道.本工作合成了单相Ag_2S化合物,系统研究了其在300—600 K范围的物相变化、离子迁移特性和电热输运性质.研究发现, Ag_2S在300—600 K温度区间表现出半导体的电输运性质.由于单斜-体心立方相晶体结构转变, Ag_2S的离子电导率、载流子浓度、迁移率、电导率、泽贝克系数等性质在455 K前后出现急剧变化.在550 K, Ag_2S的功率因子最高可达5μW·cm~(–1)·K~(–2). Ag_2S在300—600 K温度区间均表现出本征的低晶格热导率(低于0.6 W·m~(–1)·K~(–1)). S亚晶格中随机分布的类液态Ag离子是导致b-Ag_2S体心立方相具有低晶格热导率的主要原因.在573 K, Ag_2S的热电优值可达0.55,与Ag_2Se, Ag_2Te, CuAgSe等已报道的Ag基快离子导体热电材料的性能相当.  相似文献   

20.
杨家霁  李雪晶  贾艳华  张弜  蒋庆林 《中国物理 B》2022,31(2):27302-027302
Thermoelectric(TE)energy harvesting can effectively convert waste heat into electricity,which is a crucial technology to solve energy concerns.As a promising candidate for energy conversion,poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)has gained significant attention owing to its easy doping,high transparency,and solution processability.However,the TE performance of PEDOT:PSS still needs to be further enhanced.Herein,different approaches have been applied for tuning the TE properties:(i)direct dipping PEDOT:PSS thin films in ionic liquid;(ii)post-treatment of the films with concentrated sulfuric acid(H2SO4),and then dipping in ionic liquid.Besides,the same bis(trifluoromethanesulfonyl)amide(TFSI)anion and different cation salts,including 1-ethyl-3-methylimidazolium(EMIM+)and lithium(Li+),are selected to study the influence of varying cation types on the TE properties of PEDOT:PSS.The Seebeck coefficient and electrical conductivity of the PEDOT:PSS film treated with H2SO4EMIM:TFSI increase simultaneously,and the resulting maximum power factor is 46.7μW·m-1·K-2,which may be attributed to the ionic liquid facilitating the rearrangement of the molecular chain of PEDOT.The work provides a reference for the development of organic films with high TE properties.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号