LixNayCoO2的制备和热电性质

用固相反应方法，成功地合成了具有交互生长结构的Li_xNa_yCoO₂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Na_xCoO₂体系约高出60μV/K. 基于空穴载流子具有O2p特征，提出Li_xNa_yCoO₂中额外的热电势来源于氧空穴的占位熵. 关键词： xNa_yCoO₂')" href="#">Li_xNa_yCoO₂ 热电势 热电材料     

Suppressed Thermal Conductivity in Polycrystalline Gold Nanofilm: The Effect of Grain Boundary and Substrate

We investigate the electrical conductivity and thermal conductivity of polycrystalline gold nanofilms,with thicknesses ranging from 40.5nm to 115.8 nm,and identify a thickness-dependent electrical conductivity,which can be explained via the Mayadas and Shatzkes(MS)theory.At the same time,a suppressed thermal conductivity is observed,as compared to that found in the bulk material,together with a weak thickness effect.We compare the thermal conductivity of suspended and supported gold films,finding that the supporting substrate can effectively suppress the in-plane thermal conductivity of the polycrystalline gold nanofilms.Our results indicate that grain boundary scattering and substrate scattering can affect electron and phonon transport in polycrystalline metallic systems.     

微纳尺度热能调控的声子学元器件研究进展

声子是半导体材料中热能的主要载体.通过对声子调控的深入研究,人们可以为微纳电子器件散热和热能转换提供有效的解决方案.文章介绍了热能调控声子学元器件的研究进展,重点阐述了理论上如何利用微纳米结构材料构建声子学基本单元——热二极管/热整流器.此外,文章还介绍了该领域的关键测量技术和实验进展,包括热整流器和热存储器的设计与实现.最后对声子学研究的发展趋势进行了展望,并提出了存在的困难和挑战.     

Sr2RuO4的电子相干态: Nernst效应研究

文章首次报道了自旋三重态奇异配对超导体Sr2RuO4的Nernst效应在正常态呈现出的反常行为.在T<100K时,较大的负的Nernst信号出现,其绝对值随温度降低而增大,并在T* ≈ 20-25K时出现一个负的最大值,之后随温度线性减小.这样大的Nernst信号是与正常态的多带性质相关,而非线性的磁场关系则可能与其中的磁涨落相关.文章作者提出在T*温度以下,在电子型的γ带上出现了能带关联的相干态,准粒子的散射受到了抑制,使得在T*温度以下Nernst信号快速减弱.同时,热电势在T*附近出现了拐点,Hall系数开始发散,进一步支持了文章作者提出的观点.     

高分子聚合物热输运调控的研究进展

高分子聚合物基热界面材料对高密度集成电路的散热起到至关重要的作用。本文主要阐述 高分子聚合物热导率的理论及实验研究进展,重点介绍近年来关于调控高分子聚合物热导率的相 关工作。此外,本文还对高分子聚合物热输运调控的发展趋势进行了展望,讨论目前研究中尚未 解决的问题及瓶颈。     

Metal--Insulator Transition in Ca-Doped Sr14-xCaxCu24O41 Systems Probed by Thermopower Measurements

High quality Sr14-xCaxCu24O41 single-crystals are successfully grown by floating-zone technique, and the trans- port properties are studied. The temperature dependence of resistivity along the c-axis direction is semiconductor- like for x ≤ 10 and it can be fitted by the thermal activation equation p = po exp（ △ /kBT） with kB being the Boltzmann constant and A the activation energy. A break in the slope of thermopower （S） versus the inverse temperature （1 IT） corresponding to the formation of charge-density waves （CD W） is first observed for x ≤ 6. The temperature dependence of thermopower becomes metallic for x ≥ 8 while the resistivity is still semiconductorlike. We propose that the insulation behaviour of the resistivity in the Ca doping range 8 ≤ x ≤ 11 could result from the localization of the charge carriers due to the disorder induced by Ca doping and a revised electronic phase diagram is derived based on our observations.     

Effect of magnetic field on the spin-Peierls transition in single-crystal CuGeO

This paper reports that high quality CuGeO3 single crystals were successfully grown by floating-zone technique and the magnetic property was studied. The temperature dependence of magnetic susceptibility below the spin-Peierls （SP） transition temperature （Tsp） under magnetic fields applying along both the a- and c-axis direction can be fitted well by a model of noninteracting dimmers. The spin gap derived from the fitting is consistent with other reports. There is a very weak anisotropy in the fitting parameters for different directions, which should be expected from a SP system. A small upturn in susceptibility at low temperature due to paramagnetic impurities and/or defects can be observed. A suppression of the upturn by magnetic field is first discovered in this system and the possible origins for this suppression are discussed.     

LixNayCoO2的制备和热电性质

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60 μV/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.     

Al2O3基导热聚合物中的热逾渗网络

添加高导热填料的有机聚合物是最常用的一种热界面材料.其中一种提升热导率的方式是采用不同形貌填料复合添加,结合各种填料的优点,取长补短.然而,由于有效介质理论的局限性,以及热逾渗理论的滞后研究,对于不同形貌填料的协同机制依旧缺乏探索.为了剔除不同材料的耦合影响,本文采用不同形貌的同种氧化铝作为填料,分别制备了添加氧化铝球、氧化铝片以及球/片1∶1混合的环氧树脂复合材料.通过稳态法测量样品的热导率,发现球/片1∶1混合样品热导率得到显著提升.结合热逾渗理论,以及对填料微观分析的观测,发现片状和球状填料复合添加的协同作用对热逾渗网络有促进作用.