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1.
High‐density polycrystalline samples (above 98% of the theoretical density) of Ag8GeTe6 were prepared by solid‐state reactions of Ag2Te, GeTe, and Te, followed by hot‐pressing. The thermoelectric properties were measured at temperatures ranging from room temperature to around 700 K. The thermal conductivity values were extremely low (0.25 Wm–1 K–1 at room temperature), and consequently Ag8GeTe6 exhibited a relatively high thermoelectric figure of merit, ZT = 0.48 at 703 K. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

2.
Thermal conductivity (λ) of nanocrystalline La1−xAgxMnO3 (x=0.05, 0.15, 0.25, 0.3) pellets prepared by pyrophoric method is reported between 10 and 300 K. Magnitude of thermal conductivity has been found to be strongly influenced by monovalent (Ag) substitution at the La site. Silver doping in LaMnO3 enhances TC of the system to ∼299 K. Qualitative nature of the temperature variation of thermal conductivity of the silver substituted lanthanum manganites remains closely similar to that for divalent doped systems. Our analysis demonstrates that in La1−xAgxMnO3 also, the mechanism of heat conduction is predominantly by phonons. The contribution of the electronic part is only ∼1% of the total λ. The spin wave contribution is also estimated close to TC, which for all the samples lies within ∼2%. At temperatures below ∼100 K, the measured data have been analyzed using phonon relaxation time method and the strengths of the various phonon scattering processes have been estimated. Our analysis further suggests strong influence of phonon scattering by 2D like defects in the thermal conductivity of monovalent doped lanthanum manganites at low temperatures (<70 K) in the ferromagnetic region.  相似文献   

3.
采用高温熔融缓冷和放电等离子烧结工艺制备了p型Ag0.5(Pb8-xSnx)In0.5Te10五元化合物.研究了Sn含量对化合物载流子传输特性及热电性能的影响规律.结果表明:在Ag0.5(Pb8-xSnx)In0.5Te10(x 关键词: 0.5(Pb8-xSnx)In0.5Te10')" href="#">Ag0.5(Pb8-xSnx)In0.5Te10 合成 载流子 热电性能  相似文献   

4.
The temperature dependence of electrical conductivity σ (77–300 K) and magnetic susceptibility χ (2–300 K) of AgxTiSe2 in the Ag1/4TiSe2 phase has been studied in order to determine the possibility of preserving the charge-density-wave state in silver-intercalated TiSe2. The behavior of χ and σ in this phase is compared with that of the starting compound TiSe2. Fiz. Tverd. Tela (St. Petersburg) 40, 2165–2167 (December 1998)  相似文献   

5.
Ga对新型远红外Te基硫系玻璃光学性能的影响   总被引:1,自引:0,他引:1       下载免费PDF全文
用传统熔融淬冷法制备了新型远红外Te基硫系玻璃(100-x)(GeTe4)-xGa (x=0, 5, 10 mol%).利用差热分析(DTA)、可见/近红外吸收光谱、红外透射光谱等技术,在GeTe4玻璃的基础上,通过引入较高配位金属Ga, 研究其对玻璃组成、结构和性能的影响,利用经典的Tauc方程计算了样品光学带隙允许的直接跃迁、允许的间接跃迁及Urbach能量.分析结果表明:在GeTe4玻璃中引入 关键词: 光学材料 硫系玻璃 光学带隙 红外光谱  相似文献   

6.
A series of phosphate glasses of composition 45P2O5–(40???x)CaO–15Na2O–xAg2O (x?=?0, 3, 6, 8, 10 and 12?mol%) with different Ag2O contents were prepared using the melt-quenching technique. The incorporated Ag2O highly influenced the increase of its transition tendency towards crystallisation and, on contrary, reduced the degree of glassification of phosphate glasses. The lowering of glass transition temperature and increase in thermal expansion were observed in glasses against Ag2O inclusions. The crystalline phase transitions of amorphous material during thermal treatment were confirmed by employing X-ray diffraction studies. As revealed by X-ray photoelectron spectroscopy, the incorporated silver oxide into phosphate glass exists in two different oxidation states, Ag2O and AgO. The pyrophosphate and metaphosphate units were predominantly occupied in glass and glass ceramics. The elastic moduli and Vicker's hardness values exhibited the decrease in phosphate glass structural compactness due to Ag2O-incorporation and these values were found to improve because of crystalline transitions.  相似文献   

7.
(Ag2)xCu1?xS, x = .2, .4, .6 and .8 nanoparticles were synthesized by the solvothermal method. The as-synthesized nanoparticles were characterized by X-ray diffraction to study the crystal structure and size. The surface morphologies of the above samples were studied using scanning electron microscope. As there is continuous shift in the lower wavelength absorption edge of the UV–VIS spectrum of these samples with concentration, (Ag2)xCu1?xS nanoparticles can be tuned to different band gap energies by varying the composition. The D.C. electrical resistance was measured in the temperature range 310–485 K. As Ag2S transforms from monoclinic to bcc at around 450 K, copper sulfide nanoparticles also shows a phase transition at around 470 K, the effects of these two transitions are seen in the resistance measurements and in the UV–VIS spectra of the entire system. The electrical resistance of (Ag2)xCu1?xS nanoparticles rapidly reduces as more and more copper sulfide is added.  相似文献   

8.
A study of electronic conductivity using the DC polarization technique has been carried out for AgI and Ag1−x Cu x I (where x=0.05, 0.15, 0.25) solid solutions over a range of temperatures from 300 K to 473 K. A diode-like current-voltage characteristics arises from microscopic p-n junctions an enhanced electronic conductivity of the order of 10−3A is observed for undoped AgI and Cu-doped AgI. Activation energies (E a) for electronic conductivity obtained from log σ−1 cm−1) vs. 1000/T (K−1) were 0.48, 0.6, 0.74 and 1.01 eV for AgI, Ag0.95Cu0.05I, Ag0.85Cu0.15I and Ag0.75Cu0.25I solid solutions respectively. The near-twofold increase in activation energy (1.01 eV) observed upon 25% Cu doping is due to the substantial concentration of current carriers/holes injected by Cu while replacing Ag+ in AgI. Based in part on the paper presented at first National Conference on Nanoscience and Technology, National Chemical Laboratory, Pune, 7–8 March 2005.  相似文献   

9.
张贺  骆军  朱航天  刘泉林  梁敬魁  李静波  刘广耀 《中国物理 B》2012,21(10):106101-106101
Polycrystalline p-type Ag 0.9 Sb 1.1 x Mn x Te 2.05(x = 0.05,0.10,and 0.20) compounds have been prepared by a combined process of melt-quenching and spark plasma sintering.The sample composition of Ag 0.9 Sb 1.1 x Mn x Te 2.05 has been specially designed in order to achieve the doping effect by replacing part of Sb with Mn and to present the uniformly dispersed Ag 2 Te phase in the matrix by adding insufficient Te,which is beneficial for optimizing the electrical transport properties and enhancing the phonon scattering effect.All the samples have the NaCl-type structure according to our X-ray powder diffraction analysis.After the treatment of spark plasma sintering,only the sample with x = 0.20 has a small amount of MnTe 2 impurities.The thermal analysis indicates that a tiny amount of Ag 2 Te phase exists in all these samples.The presence of the MnTe 2 impurity with high resistance and high thermal conductivity leads to the deteriorative thermoelectric performance of the sample with x = 0.20 due to the decreased electrical transport properties and the increased thermal conductivity.In contrast,the sample with x = 0.10 exhibits enhanced thermoeletric properties due to the Mn-doping effect.A dimensionless thermoelectric figure of merit of 1.2 is attained for the sample with x = 0.10 at 573 K,showing promising thermoelectric properties in the medium temperature range.  相似文献   

10.
Single crystals of CuxAg1−x InS2 solid solutions are grown by the moving solvent method. The compositions and structures of the single crystals are determined. The thermal expansion coefficients of these crystals are determined with a dilatometer. The thermal expansion coefficients are found to vary linearly with concentration x. The thermal conductivity of the crystals is measured by the absolute method, and the concentration dependence of the thermal conductivity is constructed. This dependence is shown to have a minimum near the equimolar composition.  相似文献   

11.
Temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) have been employed to study the adsorption and photon-induced decomposition of Mo(CO)6. Mo(CO)6 adsorbs molecularly on a Pt(1 1 1) surface with weak interaction at 100 K and desorbs intact at 210 K without undergoing thermal decomposition. Adsorbed Mo(CO)6 undergoes decarbonylation to form surface Mo(CO)x (x ? 5) under irradiation of ultraviolet light. The Mo(CO)x species can release further CO ligands to form Mo adatoms with CO desorption at 285 K. In addition, a fraction of the released CO ligands transfers onto the Pt surface and subsequently desorbs at 350-550 K. The resulting Mo layer deposited on the Pt surface is nearly free of contamination by C and O. The deposited Mo adatoms can diffuse into the bulk Pt at temperatures above 1070 K.  相似文献   

12.
The alloys with the general formula of Bi85Sb15−xAgx (x=0, 1, 3, 5, 7) were prepared by mechanical alloying and subsequent pressureless sintering (Bi85Sb15 alloy was used for comparison). Their transport properties involving electrical conductivity, Seebeck coefficient, and thermal conductivity had been investigated in the temperature range of 80-300 K. The maximum absolute value of Seebeck coefficient (120 μV/K) was found at 160 K in the alloy Bi85Sb15−xAgx (x=3). The figure-of-merit of alloy Bi85Sb15−xAgx (x=1) reached a maximum value of 2.16×10−3 K−1 at 219 K, which is as large again as that of the reference sample Bi85Sb15.  相似文献   

13.
A modified random‐element isodisplacement model has been developed and used to calculate the concentration dependence of the wavenumbers of Raman‐active modes in mixed crystal system, TiS2−xSex(0≤x≤2). Earlier theoretical work, based on the Jaswal model, predicted a phase transition in this system on cooling up to 125 K temperature for the composition x ≥ 1.2. But recently reported resistivity measurements did not find the existence of any phase transition for a composition x < 1.4 on cooling. Our calculations show these findings and give remarkably better fitting to Raman data. The estimated values of the force constants are found to lie generally in the range 105–106 amu cm−2. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

14.
张增院  郜小勇  冯红亮  马姣民  卢景霄 《物理学报》2011,60(1):16110-016110
利用直流磁控反应溅射技术,通过调节反应气压(RP),在250 ℃衬底温度下制备了一系列氧化银 (AgxO) 薄膜,并利用X射线衍射谱、能量色散谱和分光光度计重点研究了RP对AgxO薄膜的结构和光学性质的影响. 研究结果表明,随着RP从0.5 Pa升高到3.5 Pa,薄膜明显呈现了从两相(AgO+Ag2O)到单相(Ag2O)结构再到两相(Ag2O+AgO)结构的演变. 特 关键词: 氧化银薄膜 直流磁控反应溅射 X射线衍射谱 光学性质  相似文献   

15.
Partially filled polycrystalline p‐type skutterudites of nominal compositions Ybx Co3FeSb12 were synthesized and their thermoelectric properties characterized. The compositions and filling fractions were confirmed with a combination of Rietveld refinement and elemental analysis. The thermoelectric properties were evaluated from 300 K to 810 K. The Seebeck coefficient and resistivity increase while the thermal conductivity decreases with increasing Yb content. A maximum ZT value of 0.85 was obtained at 810 K. This work is part of a continuing effort to enhance the thermoelectric properties of p‐type skutterudites, as this class of materials continues to be of interest for thermoelectrics applications. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

16.
A study of the structure change with temperature in amorphous Fe100xPx (13 x 24) alloys was carried out by measuring magnetization and thermal expansion and also by structural analysis using X-ray diffraction and differential thermal analysis (DTA). The structure of the amorphous alloys relaxes (the decrease of excess free volume) at temperatures 100–150 K below the crystallization temperatures. The alloys with x 15 transform into (α-Fe + amorphous) at about 600 K. The alloys with x15 transform into (α-Fe+amorphous+Fe3P) at about 600 K. With further heating, the alloys transform into (α-Fe+Fe3P) both of which are stable phases from the equilibrium phase diagram.  相似文献   

17.
熊聪  邓书康  唐新峰  祁琼  张清杰 《物理学报》2008,57(2):1190-1196
用高温熔融结合放电等离子烧结法制备了Zn掺杂单相n型Ba8Ga16-2xZnxGe30+x笼合物,探索了Zn对Ga的取代对其热电传输特性的影响规律.研究结果表明,n型Ba8Ga16-2xZnxGe30+x化合物的电导率随着x的增加逐渐增 关键词: 热电传输性能 n型笼合物 框架取代  相似文献   

18.
This paper presents a study of bulk samples synthesized of the Ag1−xCuxInSe2 semiconductor system. Structural, thermal and electrical properties, as a function of the nominal composition (Cu content) x=0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 were studied. The influence of x on parameters such as melting temperature, solid phase transition temperature, lattice parameters, bond lengths, crystallite size t (coherent domain), electrical resistivity, electrical mobility and majority carrier concentration was analyzed. The electrical parameters are analyzed at room temperature. In general, it is observed that the properties of the Ag1−xCuxInSe2 system for x≤0.4 are dominated by n-AgInSe2, while for x>0.4, these are in the domain of p-CuInSe2. The crystallite size t in the whole composition range (x) is of the order of the nanoparticles. Secondary phases (CuSe, Ag2Se and InSe) in small proportion were identified by XRD and DTA.  相似文献   

19.
The magnetic susceptibility and magnetization are presented for polycrystalline samples of the alloy systems Cd1-xMnxTe 0 < x 0.1 and Sn1-xMnxTe 0 < 4 0.4. The magnetic measurements were performed between 2.3 K and 300 K in external magnetic fields up to 11 kOe. At sufficiently high temperatures the susceptibility can be described by a Curie-Weiss law. In the system Sn1-xMnxTe θp is positive. A linear dependence θpx was found with θp(0.4) = 49 K. In the series Cd1-xMnxTe θp changes sign. For θ < x < 0.04 θp is positive with a maximum θp ≈ 10 K at x = 0.02. In the region x #62; 0.04 θp becomes negative with θp = -35 K at x = 0.1. The effective spin value of manganese is Seff #62; 5/2 for all the samples. The investigation was done to check the assumption that ferromagnetic coupling may exist in tellurides of manganese if the shortest distance dMnMn is greater than 3.4 Å. This hypothesis has been stated. In the case θp #62; 0 the results are partly explained by the RKKY exchange coupling.  相似文献   

20.
杜保立  徐静静  鄢永高  唐新峰 《物理学报》2011,60(1):18403-018403
采用高纯元素直接熔融、淬火并结合放电等离子烧结方法制备了非化学计量比AgSbTe2+x(x=0—0.05)系列样品,研究了不同Te含量在300—600 K范围内对样品热电性能的影响规律.结果表明:随着Te含量的增加,Ag+离子空位浓度增加,空穴浓度和电导率大幅度提高,Seebeck系数减小.热导率随Te过量程度的增加略有增加,但所有Te过量样品的晶格热导率均介于0.32—0.49 W/mK之间,低于化学计量比样品的值,接近理论最低晶格热导率.AgS 关键词: 2')" href="#">AgSbTe2 非化学计量比 热电性能 热导率  相似文献   

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