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The composition-dependent thermoelectric properties of lead telluride (PbTe) doped with bismuth telluride (Bi2Te3), antimony telluride (Sb2Te3) and (BiSb)2Te3 have been studied at room temperature. All the sampies exhibit small thermal conductivity. The figures of merit, 7.63, 1.03 and 8.97 x 10-4, have been obtained in PbTe with these dopants, respectively. These values are several times higher than those of PbTe containing other dopants with small grain sizes. The high thermoelectric performance is explained by electronic topological transition induced by alloying. The results indicate that these dopants are effective to enhance the thermoelectric performance of PbTe. 相似文献
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A new structural phase of MgV2O6 was obtained by a high-pressure,high-temperature(HPHT) synthesis method.The new phase was investigated by the Rietveld analysis of X-ray powder diffraction data,showing space group Pbcn(No.60) symmetry and a = 13.6113(6) (1 = 0.1 nm),b = 5.5809(1) ,c = 4.8566(3) ,V = 368.93(2) 3(Z = 4).High pressure behavior was studied by Raman spectroscopy at room temperature.Under 22.5 GPa,there was no sign of a structural phase transition in the spectra,demonstrating stability of the HPHT phase up to the highest pressure. 相似文献
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以高温高压为手段,在4~5GPa压力和700~1 200 K温度条件下,成功地合成出了PbTe。对合成样品进行了X射线测试分析,结果表明,合成的PbTe样品是具有NaCl结构的多晶,而PbTe的取向随着合成压力的升高发生变化。扫描电镜分析结果显示:高压合成的PbTe样品,其晶粒有了明显的取向;电阻率比常压样品低1~2个数量级,并随合成压力的升高而降低;热导率也同时低于常压合成的PbTe样品。以上结果说明,高压合成方法是改善材料性能的重要手段。 相似文献
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本文主要通过高压拉曼光谱研究了正铁氧体SmFeO3的晶格振动模式在外加压力作用下的行为规律,高压实验中压力最高为29.7GPa。本文采用溶胶凝胶法,制备出具有正交结构,其空间群为Pnma的SmFeO3。在外加压力作用下,所有观察到的拉曼振动模式都呈现出宽化趋势。特别是位于621.1cm-1的FeO6八面体的反弹性振动模式Ag(1)与位于452.7cm-1的FeO6八面体的弯曲振动模式B3g(3),其压力系数出现最大值。与此相反,Sm-O振动模式Ag(7)的压力系数却非常小。这说明外加压力更容易影响到FeO6八面体的晶格变化,而不是SmO12十七面体的改变。SmFeO3的这种高压下晶格振动模式变化行为类似于G型结构的CaSnO3。同时,文中还给出了所有声子零压模式下的格林爱森参数与体弹模量的比值。这些参数可用于进一步测量单轴或者双轴的应变力,可深入理解声子频率在张力作用下移动的表现行为。 相似文献
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Structural and spectroscopic properties of Sr 2 ZnTeO 6 (SZTO) were investigated by angle-dispersive synchrotron X-ray powder diffraction and Raman spectroscopy in a diamond anvil cell up to 31 GPa at room temperature. Although SZTO remained stable up to the highest pressure, the different pressure coefficients of the normalized axial compressibility were obtained as βab =8.16×10-3 GPa-1 and βc =7.61×10-3 GPa-1 . The bulk modulus B0 was determined to be 190(1) GPa by fitting the pressure-volume data using the Birch-Murnaghan equation of state. All the observed Raman modes exhibited a broadening effect under high pressure. The vibrational band υ1 around 765 cm-1 , which is associated with the Te-O stretching mode in the basal plane of the TeO6 octahedron had the largest pressure coefficient, and the Grüneisen parameters for all the observed phonon modes were also calculated and presented. These parameters could be used to measure the amount of uniaxial or biaxial strain, providing a fundamental tool for monitoring the magnitude of the shift of phonon frequencies with strains. 相似文献
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The structural and magnetic properties of SmFeO3 with B site substitution of non-magnetic atom A1 are investigated. The x-ray diffraction patterns show that SmFe(1-x)AlxO3 remains an orthorhombic structure within the whole doping range, and the unit-cell volume decreases monotonically with the increase of doped A1 concentration. Besides, the octa- hedral tilting distortions of FeO6 are found to be alleviated while the tolerance factor increases. However, the relationship between the lattice parameters and Al concentration is observed to deviate from Vegard's rule, and this may be caused by magnetostriction effects. For the doping content values in a range 0 〈 x 〈 0.6, the ferromagnetism, antiferromagnetism, and paramagnetism are observed to occur continuously. Moreover, the magnetization and the spin reorientation temperature (Tk) decrease monotonically as Al content value increases. With the doping content values being x = 0.8 and 1.0, these compounds only show paramagnetic behavior. 相似文献
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The high-pressure behaviors of SmFeO3 are investigated by angle-dispersive synchrotron X-ray powder diffraction under a pressure of up to 40.3 GPa at room temperature. The crystal structure of SmFeO3 remains stable at up to the highest pressure. The different pressure coefficients of the normalized axial compressibility are obtained to be βa = 0.60 × 10-3 GPa-1,βb = 0.79 × 10-3 GPa-1, βc = 1.28 × 10-3 GPa- 1, and the bulk modulus (B0) is determined to be 293(3) GPa by fitting the pressure-volume data using the Birch-Murnaghan equation of state. Furthermore, the larger compressibility of the FeO6 octahedra suggests the evolution of the orthorhombic structure towards higher symmetry configuration at high pressures. 相似文献
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Structural stability and electrical properties of AIB2-type MnB2 under high pressureStructural stability and electrical properties of AIB2-type MnB2 under high pressureStructural stability and electrical properties of AIB2-type MnB2 under high pressureStructural stability and electrical properties of AIB2-type MnB2 under high pressure 下载免费PDF全文
The structural stability and electrical properties of A1B2-type MnB2 were studied based on high pressure angle- dispersive x-ray diffraction, in situ electrical resistivity measured in a diamond anvil cell (DAC) and first-principles calcu- lations under high pressure. The x-ray diffraction results show that the structure of A1B2-type MnB2 remains stable up to 42.6 GPa. From the equation of state of MnB2, we obtained a bulk modulus value of 169.9~3.7 GPa with a fixed pressure derivative of 4, which indicates that A1B2-type MnB2 is a hard and incompressible material. The electrical resistance un- dergoes a transition at about 19.3 GPa, which can be explained by a transition of manganese 3d electrons from localization to delocalization under high pressure. 相似文献