共查询到19条相似文献,搜索用时 143 毫秒
1.
2.
3.
4.
5.
测量了MgB2的热电势和电阻率与温度的依赖关系.在100K—300K区间,热电势呈近似线性温度依赖关系,其斜率为正,表明载流子为空穴型且与能带贡献的图像相一致.与此对应,在此温区电阻率呈T2依赖关系.在100K以下,热电势和电阻率各自转变了其高温区的温度依赖关系.热电势在超导转变温度Tc(零电阻366K)到100K间有一宽峰,具有声子曳引峰的特征,表明电子-声子相互作用很强.估算了一些重要的参数,如带米能EF、能带宽度
关键词:
新型超导体
热电势
电阻率 相似文献
6.
本文发展文献[1]的方法到两种不同自旋的原子(Sa=1,Sb=1/2)构成的晶格中,计算了简单立方晶格在具有再次近邻反铁磁相互作用下在外磁场中的基态自旋结构、能量和相界。从文中给出的相图可知:这种晶格有两种反铁磁自旋结构,有四种亚铁磁自旋结构。
关键词: 相似文献
7.
8.
9.
Mg3(Sb,Bi)2基热电材料由于其优异的热电性能和较低的成本近来受到广泛的关注.本研究通过将纳米SiO2复合进成分为Mg3.275Mn0.025Sb1.49Bi0.5Te0.01的基体相中,考察其热电输运性能的变化及机制.结果表明,当SiO2复合进Mg3Sb2基材料中时,由于引进大量的微小晶界,能有效地散射声子,促使晶格热导率降低,优化热输运性能,如SiO2体积含量为0.54%时,室温时热导率由复合前的1.24 W/(m·K)降至1.04 W/(m·K),降幅达到15%;同时其对电子也产生强烈的散射作用,导致迁移率和电导率大幅下滑,结果表现为近室温区功率因子剧烈衰减,恶化了电输运性能.电性能相对于热性能较大降低幅度使得材料在整个测试温区的热电优值没有得到改善.纳米SiO2作为Mg3Sb2 相似文献
10.
本文用X射线粉末法测定了Li2K(IO3)3与Li2NH4(IO3)3的晶体结构和原子参数。发现Li3K(IO3)3,Li2NH4(IO3)3与Li2Rb(IO3)3同晶型,属单斜晶系,空间群为P21/α,每个单胞含有四个化合式量。室温的点阵常数分别为α=11.198?,b=11.046?,c=8.254?,β=111.53°,及α=11.327?,b=11.078?,c=8.341?,β=111.87°。讨论了二元化合物的形成与离子半径的关系。
关键词: 相似文献
11.
K. Rogacki K. Oganisian N. Zhigadlo J. Karpinski 《Journal of Physics and Chemistry of Solids》2008,69(12):3202-3204
The thermoelectric power of C, Mn, C:Li, and Al:Li substituted MgB2 single crystals has been investigated in the temperature range 10-300 K. Both the in-plane (Sab) and the out-of-plane (Sc) thermopowers are positive for the non-substituted crystal and both Sab and Sc change a sign for crystals doped with electrons where C is substituted for B in the amount larger than 5 at%. When Li is substituted for Mg, the π band rather than the σ band is doped with holes and the doping effects are much more subtle. The anisotropy ratio of the non-substituted crystal Sab/Sc≈3 and this ratio is strongly reduced by the substitution of C. Isovalent magnetic Mn ions, which substitute for Mg with a drastic reduction of Tc, do not influence the values and temperature dependences of both Sab and Sc. 相似文献
12.
The pressure dependence of the thermoelectric power of monoclinic As2Te3 is measured up to 10 GPa using a Mao-Bell diamond anvil cell. The thermoelectric power never reaches an absolute value greater than the ambient pressure value of 242 μV/K. Evidence of a phase transition is present between 6 and 8 GPa where the thermoelectric power reaches an absolute value of 225 μV/K after passing through a minimum of S≈75 μV/K. X-ray diffraction experiments confirm that the resulting structure is β-As2Te3, which is isostructural with Bi2Te3 and Sb2Te3. 相似文献
13.
Recently, Gamal et al. [Chin. Phys. Lett. 22 (2005) 1530] reported the results of electrical conductivity, Hall effect and thermoelectric measurements on p-type Tl2S5 single crystals. From the experimental data for the temperature dependence of differential thermoelectric power, Gamal et al. determined thevalues of 2.66×10-41kg and 2.50×10-41kg, respectively, for the effective masses of electrons and holes in p-type Tl2S5, which are about ten orders of magnitude smaller than the free electron mass (9.11×10-31kg). We argue that the anomalously small values obtained for the effective mass of chargecarriers in Tl2S5 have no physical significance. 相似文献
14.
We have used the technique of chemical vapour transport to prepare needle shaped single crystal of ZrS3. Results of the measurements of d.c. resistivity. Hall coefficient and thermoelectric power of the temperature range 100–500 K are reported. All the samples exhibited semiconducting behaviour with a room temperature resistivity of about 15 Ω-cm and an activation energy of 0.20±0.02 eV. Room temperature thermoelectric power is -850 μVK?1 and the dominant carriers are electrons. The thermoelectric power varies as (1/T), a behaviour associated with a typical semiconductor. Mobility at low temperatures is limited by ionized impurity scattering and is given by μ1 = 6.5 × 10?2T3/2 cm2V7-1 sec?1. At high temperatures, phonon scattering is dominant and the mobility is given by μ2 = 1.35 × 10+5T?32 cm2V?1 sec?1. 相似文献
15.
High temperature thermoelectric properties of highly c-axis oriented Bi2Sr2Co2Oy thin films fabricated by pulsed laser deposition 下载免费PDF全文
High-temperature thermoelectric transport property measurements have been performed on the highly c-axis oriented Bi2Sr2Co20v thin films prepared by pulsed laser deposition on LaA1Oa (001). Both the electric resistivity p and the seebeck coefficient S of the film exhibit an increasing trend with the temperature from 300 K-1000 K and reach up to 4.8 m. cm and 202 V/K at 980 K, resulting in a power factor of 0.85 mW/mK which are comparable to those of the single crystalline samples. A small polaron hopping conduction can be responsible for the conduction mechanism of the film at high temperature. The results demonstrate that the Bi2Sr2Co2Oy thin film has potential application has high temperature thin film thermoelectric devices, 相似文献
16.
K.Z RushchanskiiH Haeuseler D.M Bercha 《Journal of Physics and Chemistry of Solids》2002,63(11):2019-2028
For the compounds FeGa2S4 and NiGa2S4 band structure calculations have been performed by the ab initio plane wave pseudo-potential method. The valence charge density distribution points to an ionic type of chemical bonding between the transition metal atoms and the ligand atoms. Two models for the pseudo-potentials are used to calculate the band structures: (a) only s and p electrons and (b) also the d-shells of the transition metal atoms are included in the pseudo-potentials. The differences between these two cases of band structures are discussed. Energy gap formation peculiarities are analysed for both crystals. Zak's elementary energy band concept is demonstrated for the energy spectra of the considered crystals. 相似文献
17.
We have investigated FeMo2S4 by transmission Mössbauer spectroscopy on the 57Fe nucleus between 4.2 and 1037 K, using both powdered and single crystal samples.The temperature dependences of the isomer shift and the quadrupole splitting indicate the existence of ferrous ions with well localized 3d electrons. The two different crystallographic Fe sites cannot be separated over the experimental temperature range. The local symmetry of the iron site is lower than axial (η ~ 0.47) and the crystal field splittings Δ1 and Δ2 of the Fe2+ ? T2g Orbitals, estimated by the Ingalls' method, are close to 250 and 900 cm?1.The hyperfine field makes an angle of 14° with the normal on the plane (a, b), deviating a little from the direction of the magnetic moments determined to be perpendicular to (a, b) by neutron diffraction study.At higher temperatures, and more particularly near TN, a line broadening is observed, and the spectra have to be fitted by a hyperfine field distribution. The broadening comes from the presence of about 7% “abnormal” Fe-sites observed in the paramagnetic spectra, and whose origin is discussed.The Néel temperature was determined to be 112 ± 1 K for the powdered sample and 106 ± l K for the single crystal. 相似文献
18.
The thermoelectric power of linear chain synthetic metals Nb3X4 (with X=S, Se and Te) was measured from 5 to 300 K. The thermopower is negative indicating a dominant transport by electrons. Common to three compounds, in lower temperature regions the thermopower rises linearly with temperature but soon saturates. With respect to Nb3S4 and Nb3Se4 we have found no special anomaly of the thermopower except for a little higher magnitude.With respect to Nb3Te4 anomalies in the thermopower vs temperature appear at about 80 and 20 K which are explained in terms of the charge- density-wave phase transition from the simultaneous measurement of the resistivity and the observation of the electron diffraction patterns. 相似文献
19.
Quantum oscillations have been observed in the thermoelectric power and thermal conductivity coefficients of a semiconductor Cd3As2 single crystal. Theoretical expressions for these coefficients, taking into account the Landau level broadening, are derived in this paper. The good agreement found between the thermoelectric power measurements and the corresponding theoretical expressions for the temperature and magnetic field dependence of the quantum oscillation amplitudes and the absolute values of the amplitudes has allowed us to calculate effective mass values which are in agreement with Shubnikov-de Haas measurements. 相似文献