热电型太赫兹探测器响应度校准技术

为保证太赫兹辐射强度测量的准确可靠,对热电型太赫兹探测器的响应度进行了校准。首先,基于替代法构建了太赫兹探测器响应度校准装置,该装置的合成标准不确定度为2.4%。然后,在1.63 THz频率点处,利用校准装置对12D-3S-VP型太赫兹探测器进行了校准,得到的响应度校准结果为197.6 mV/W,与厂家标称值一致。对自主研制的热电型太赫兹探测器进行了校准,得到的响应度和合成标准测量不确定度分别为362.2 mV/W和2.7%。最后,将校准结果的标准偏差值与合成标准不确定度进行了比较,发现标准偏差值在合理范围内,这进一步证明了校准方法、校准结果以及不确定度分析的合理性。     

An Orthorhombic Phase of Superhard o-BC_4N

A potential superhard o-BC_4 N with Imm2 space group is identified by ab initio evolutionary methodology using CALYPSO code. The structural, electronic and mechanical properties of o-BC_4N are investigated. The elastic calculations indicate that o-BC_4N is mechanically stable. The phonon dispersions imply that this phase is dynamically stable under ambient conditions. The structure of o-BC_4N is more energetically favorable than o-BC_4N above the pressure of 25.1 GPa. Here o-BC_4N is a semiconductor with an indirect band gap of about 3.95 eV, and the structure is highly incompressible with a bulk modulus of 396.3 GPa and shear modulus of 456.0 GPa. The mechanical failure mode of o-BC_4N is dominated by the shear type. The calculated peak stress of 58.5 GPa in the(100)[001] shear direction sets an upper bound for its ideal strength. The Vickers hardness of o-BC_4N reaches 78.7 GPa, which is greater than that of t-BC_4N and bc-BC_4N proposed recently, confirming that o-BC_4N is a potential superhard material.     

Mg2Si的电子结构和热电输运性质的理论研究

利用全势线性缀加平面波法,对Mg₂Si的几何结构和电子结构进行了计算,得到了稳定的晶格参数以及能带和电子态密度.能带结构表明,Mg₂Si为间接带隙半导体,禁带宽度为020 eV.在此基础上利用玻尔兹曼输运理论和刚性带近似计算了材料的电导率、Seebeck系数和功率因子.结果表明,在温度为700 K时p型和n型掺杂的Mg₂Si功率因子达到最大时的最佳载流子浓度分别为7749×10¹⁹ cm^-3和 关键词： 2Si')" href="#">Mg₂Si 全势线性缀加平面波法 热电输运性质     

双掺杂锰酸钙基热电陶瓷的制备及电学性能研究

利用传统固相反应法成功制备出Nb掺杂量x不同的Ca_0.9Yb_0.1Mn_1-xNb_xO₃热电陶瓷. X射线衍射分析和扫描电子显微镜分析表明: 样品均形成了单一的钙钛矿正交结构,空间群为Pnma. 晶格常数a和晶胞体积随着Nb掺杂量x的增加而增大,陶瓷样品具有很好的结晶度和很高的致密性, 相对密度达到97%左右. 在3 关键词： 3陶瓷')" href="#">CaMnO₃陶瓷 电阻率 Seebeck系数     

火焰原子吸收光谱法测定太空诱变育种黄芩中微量元素

太空育种,即空间诱变育种,是利用太空技术,通过卫星、飞船等航天器将植物的种子、组织、器官或生命个体等诱变材料搭载到宇宙空间,利用强辐射、微重力、高真空、弱磁场等宇宙空间特殊环境诱变因子的作用,使生物基因发生变异,再返回地面进行选育,培育新品种、新材料的作物育种新技术。新     

烧结温度对La0.9Sr0.1FeO3热电性能的影响

利用传统的固相反应分别在1250℃,1300℃,1350℃.烧结条件下制备出钙钛矿结构的La_0.9Sr_0.1FeO₃陶瓷样品.样品的XRD粉末衍射结果显示不同烧结温度的La_0.9Sr_0.1FeO₃陶瓷样品都是单相的正交结构,同时晶胞体积随着烧结温度的升高而减小.从样品的SEM结果看出,随着烧结温度的升高,晶粒逐渐变大,并且晶粒间的空隙逐渐减小,样品更加致密.在室温到800℃的 关键词： 铁酸镧陶瓷 热电性能 烧结温度     

Strategies for optimizing the thermoelectricity of PbTe alloys

The thermoelectric materials have been considered as a potential candidate for the new power generation technology based on their reversible heat and electricity conversion.Lead telluride(Pb Te) is regarded as an excellent mid-temperature thermoelectric material due to its suitable intrinsic thermoelectric properties.So tremendous efforts have been done to improve the thermoelectric performance of Pb Te,and figures of merit,z_T 2.0,have been reported.Main strategies for optimizing the thermoelectric performance have been focused as the main line of this review.The band engineering and phonon scattering engineering as two main effective strategies are systemically summarized here.The band engineering,like band convergence,resonant levels,and band flatting have been addressed in improving the power factor.Additionally,phonon scattering engineerings,such as atomic-scale,nano-scale,meso-scale,and multi-scale phonon scatterings have been applied to reduce the thermal conductivity.Besides,some successful synergistic effects based on band engineerings and phonon scatterings are illustrated as a simultaneous way to optimize both the power factor and thermal conductivity.Summarizing the above three main parts,we point out that the synergistic effects should be effectively exploited,and these may further boost the thermoelectric performance of Pb Te alloys and can be extended to other thermoelectric materials.     

烧结温度对La0.1Sr0.9TiO3陶瓷热电性能的影响

利用传统固相反应方法, 分别在1440℃, 1460℃, 1480℃和1500℃烧结条件下, 制备了钙钛矿结构的La_0.1Sr_0.9TiO₃陶瓷样品. 样品的粉末X射线衍射结果显示, 不同烧结温度的La_0.1Sr_0.9TiO₃ 陶瓷样品均为单相的正交结构. 从样品的扫描电子显微照片来看, 随着烧结温度的增加, 平均晶粒尺寸逐渐增大. 在室温至800℃的测试温区, 测试了样品的电阻率和Seebeck系数, 系统地研究了不同烧结温度对样品热电性能的影响. 结果表明, 样品的电阻率在测试温区内随着测试温度的升高先略微降低, 然后逐渐升高;总体来看, 样品的电阻率随烧结温度的升高先增大后降低. 在测试温区内, Seebeck系数均为负值, 表明样品的载流子为电子; 随着测试温度的升高, Seebeck系数绝对值均有所增大;随烧结温度升高, Seebeck系数绝对值逐渐增大后显著降低. 1480℃制备的样品因其相对较低的电阻率和相对较高的Seebeck系数绝对值, 在165℃时得到最大的功率因子21 μW·K^-2·cm^-1.     

Nb掺杂对还原性烧结的TiO2-δ陶瓷的晶体结构及热电性能的影响

利用传统的固相反应法在还原性气氛1200 ℃下分别制备出不同Nb掺杂量的Ti_1-xNb_xO_2-δ陶瓷样品.样品的粉末X射线衍射(XRD)结果显示:Nb掺杂量x较低时样品为多相混合,当Nb掺杂量x>0.02时样品为单一的四方相金红石型结构.在室温到900 K的测试温区,测试了单相样品(x=0.02,0.03,0.04)的电导率、Seebeck系数和热导率.测试 关键词： 氧化钛陶瓷 热电性能 氧空位     

Theoretical investigation of the thermoelectric transport properties of BaSi2

The full-potential linear augmented plane wave method based on density functional theory is employed to investigate the electronic structure of BaSi 2 . With the constant relaxation time and rigid band approximation,the electrical conductivity,Seebeck coefficient and figure of merit are calculated by using Boltzmann transport theory,further evaluated as a function of carrier concentration. We find that the Seebeck coefficient is more anisotropic than electrical conductivity. The figure of merit of BaSi 2 is predicted to be quite high at room temperature,implying that optimal doping may be an effective way to improve thermoelectric properties.