共查询到20条相似文献,搜索用时 31 毫秒
1.
L.Q. ZhangZ.Z. Ye J.Y. Huang B. LuH.P. He J.G. LuY.Z. Zhang J. JiangJ. Zhang K.W. WuW.G. Zhang 《Journal of Alloys and Compounds》2011,509(27):7405-7409
A series of K doped Zn1−xMgxO thin films have been prepared by pulsed laser deposition (PLD). Hall-effect measurements indicate that the films exhibit stable p-type behavior with duration of at least six months. The band gap of the K doped Zn1−xMgxO films undergoes a blueshift due to the Mg incorporation. However, photoluminescence (PL) results reveal that the crystallinity decreased with the increasing of Mg content. The fabricated K doped p-type Zn0.95Mg0.05O thin film exhibits good electrical properties, with resistivity of 15.21 Ω cm and hole concentration of 5.54 × 1018 cm−3. Furthermore, a simple ZnO-based p-n heterojunction was prepared by deposition of a K-doped p-type Zn0.95Mg0.05O layer on Ga-doped n-type ZnO thin film with low resistivity. The p-n diode heterostructure exhibits typical rectification behavior of p-n junctions. 相似文献
2.
H. Le-Quoc A. LacosteA. Bès T. Tan VinhD. Fruchart N. Skryabina 《Journal of Alloys and Compounds》2011,509(41):9906-9911
Magnesium stannide (Mg2Sn) thin films doped with Ag intended for thermoelectric applications are deposited on both silicon and glass substrates at room temperature by plasma assisted co-sputtering. Characterization by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction confirms the formation of fine-grained polycrystalline thin films with thickness of 1-3 μm. Stoichiometry, microstructure and crystal structure of thin films are found to vary with target biasing and the distance from targets to substrate. Measurements of electrical resistivity and Seebeck coefficient at room temperature show the maximum power factor of ∼5.0 × 10−3 W K−2 m−1 for stoichiometric Mg2Sn thin films doped with ∼1 at.% Ag. 相似文献
3.
Xian-Zhong XiongZhan-Guo Liu Jia-Hu Ouyang Xiao-Liang XiaJun Xiang Xiao-Ming Liu 《Journal of Alloys and Compounds》2011,509(33):8392-8397
The pyrochlore-type phases with the compositions of SmDy1−xMgxZr2O7−x/2 (0 ≤ x ≤ 0.20) have been prepared by pressureless-sintering method for the first time as possible solid electrolytes. The structure and electrical conductivity of SmDy1−xMgxZr2O7−x/2 ceramics have been studied by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance spectroscopy measurements. SmDy1−xMgxZr2O7−x/2 (x = 0, 0.05, 0.10) ceramics exhibit a single phase of pyrochlore-type structure, and SmDy1−xMgxZr2O7−x/2 (x = 0.15, 0.20) ceramics consist of pyrochlore phase and a small amount of the second phase magnesia. The total conductivity of SmDy1−xMgxZr2O7−x/2 ceramics obeys the Arrhenius relation, and the total conductivity of each composition increases with increasing temperature from 673 to 1173 K. SmDy1−xMgxZr2O7−x/2 ceramics are oxide-ion conductors in the oxygen partial pressure range of 1.0 × 10−4 to 1.0 atm at all test temperature levels. The highest total conductivity value is about 8 × 10−3 S cm−1 at 1173 K for SmDy1−xMgxZr2O7−x/2 ceramics. 相似文献
4.
ZnO has received much attention in the degradation and complete mineralization of environmental pollutants. For the purpose of increasing the photocatalytic efficiency of ZnO, Mg was doped into ZnO thin films.Zn1 − xMgxO thin films were prepared by spray pyrolysis method on glass substrates. The deposition temperature was 500 °C. Mg concentration was varied in the range of 0.0 to 0.3 in intervals of 0.05. The pure ZnO films were polycrystalline with preferred orientation (100). Zn1 − xMgxO becomes amorphous with increasing Mg concentration. The optical band gap of Zn1 − xMgxO changes from 3.26 to 3.59 eV with increasing Mg content. Also, the photocatalytic activity increased with Mg, and the film with x = 0.3 showed the best result. 相似文献
5.
K.-F. Chiu 《Surface & coatings technology》2010,205(5):1642-1646
LiFePO4 thin films have been sputtered from a pure LiFePO4 target onto Ag/SS, Ag/Si3N4/Si and Si3N4/Si substrates. All of the deposited films were annealed at 973 K for 1 hr in H2/Ar (5 %) atmosphere. Substrate induced microstructural and crystallographic evolutions have been observed by a scanning electron microscope and X-ray diffraction. Energy dispersion spectra and X-ray photoelectron spectra revealed that Ag was mixed in the LiFePO4 films deposited on Ag under layers. Ceramic metal composite thin films were obtained. The film conductivity (1 × 10− 3 Scm− 1) is therefore elevated by an order of six, compared with pure LiFePO4 (10− 9 Scm− 1). The electrochemical measurements of the LiFePO4-Ag films showed a flat plateau at 3.4 V (v.s. Li/Li+) and a reversible capacity of 80 mAh/g. Optimization of Ag contents may further improve the discharge capacity. 相似文献
6.
This study investigated the potential applications of microwave dielectric properties of Mg2SnO4 ceramics in mobile communication. Mg2SnO4 ceramics were prepared using a conventional solid-state method. The X-ray diffraction patterns of the Mg2SnO4 ceramics revealed no significant variation of phase with sintering temperature. A maximum density of 4.62 g/cm3, a dielectric constant (?r) of 8.41, a quality factor (Q × f) of 55,100 GHz, and a temperature coefficient of resonant frequency (τf) of −62 ppm/ °C were obtained when Mg2SnO4 ceramics were sintered at 1550 °C for 4 h. 相似文献
7.
Guobing YingXiaodong He Mingwei LiShanyi Du Wenbo HanFei He 《Journal of Alloys and Compounds》2011,509(31):8022-8027
In this work, phase pure Cr2AlC and impure Cr2AlC with Cr7C3 have been fabricated to investigate the mechanical, thermal, and electrical properties. The thermal expansion coefficient is determined as 1.25 × 10−5 K−1 in the temperature range of 25-1200 °C. The thermal conductivity of the Cr2AlC is 15.73 W/m K when it is measured at 200 °C. With increasing temperature from 25 °C to 900 °C, the electrical conductivity of Cr2AlC decreases from 1.8 × 106 Ω−1 m−1 to 5.6 × 105 Ω−1 m−1. For the impure phase of Cr7C3, it has a strengthening and embrittlement effect on the bulk Cr2AlC. And the Cr2AlC with Cr7C3 would result in a lower high-temperature thermal expansion coefficient, thermal conductivity, specific heat capacity and electrical conductivity. 相似文献
8.
J.Q. Li S.P. LiQ.B. Wang L. WangF.S. Liu W.Q. Ao 《Journal of Alloys and Compounds》2011,509(13):4516-4519
The PbSe1−xTex alloys with x = 0.2, 0.3, 0.5, 0.85 and 1.0 were prepared by induction melting, ball milling and spark plasma sintering techniques. The thermoelectric properties of the samples were investigated. The XRD analysis indicated that all samples are NaCl-type structure solid solutions Pb(Se,Te) containing nanograins. Increasing Te content resulted in increasing the lattice parameter a. The thermoelectric measurements show that all samples are n-type semiconductors in temperature range from 300 K to 673 K. The electrical resistivity of the doped sample is much smaller than that of pure PbSe, but comparable to that of PbTe. The absolute Seebeck coefficients for the doped sample PbSe1−xTex with x = 0.2, 0.3 and 0.5 range from 150 μV/K at 300 K to 250 μV/K at 673 K, which is much larger than that of pure PbSe (66-138 μV/K), but smaller than that of PbTe (230-310 μV/K) in the same experimental conditions. The thermal conductivity for the doped sample PbSe1−xTex with x = 0.2, 0.3 and 0.5 range from 0.95 to 0.66 W/m K, which is much smaller than that of pure PbSe (2.1-1.3 W/m K) or PbTe (1.4-1.1 W/m K). As a result, the figure of merit for the doped sample can be enhanced. The maximum dimensionless figure of merit ZT of 1.15 was obtained in the sample PbTe0.5Se0.5 at 573 K, more than 50% higher than that of pure PbTe prepared in the same condition. 相似文献
9.
M.J. BaniamerianS.E. Moradi 《Journal of Alloys and Compounds》2011,509(21):6307-6310
Production of hydrogen using Al-Ga doped nanostructured carbon in pure water is studied. The XRD and BET techniques were used for sample analyses. Dehydrogenation data of aluminum on the ordered mesoporous carbon were collected at 353 K. In the present work the oxidation rate of activated aluminum and water is investigated depending on eutectic composition and reaction temperature. The H2 generation rate increases with the rise of temperature. Incorporated Al-Ga-OMC nanocomposite had faster (hydrogen production rate was 112 ml H2 min−1 g−1) and more efficient (hydrogen production yield was 100%) dehydrogenation kinetics than incorporated Al-OMC nanocomposite and ball-miled active aluminum. 相似文献
10.
Chesta Ruttanapun Aree WichainchaiWutthisak Prachamon Anucha YangthaisongAnek Charoenphakdee Tosawat Seetawan 《Journal of Alloys and Compounds》2011,509(13):4588-4594
The samples of Cu1−xPtxFeO2 (0 ≤ x ≤ 0.05) delafossite were synthesized by solid state reaction method for studying thermoelectric properties. The properties of Seebeck coefficient, electrical conductivity and thermal conductivity were measured in the high temperature ranging from 300 to 960 K. The results of Seebeck coefficient, electrical conductivity and power factor were increased with increasing Pt substitution and temperature. The thermal conductivity was decreased from 5.8 to 3.5 W/mK with increasing the temperature from 300 to 960 K. An important results, the highest value of power factor and ZT is 2.0 × 10−4 W/mK2 and 0.05, respectively, for x = 0.05 at 960 K. 相似文献
11.
Ag-doped Ca3Co4O9 thin films with nominal composition of Ca3−xAgxCo4O9 (x = 0∼0.4) have been prepared on sapphire (0 0 0 1) substrates by pulsed laser deposition (PLD). Structural characterizations and surface chemical states analysis have shown that Ag substitution for Ca in the thin films can be achieved with doping amount of x ≤ 0.15; while x > 0.15, excessive Ag was found as isolated and metallic species, resulting in composite structure. Based on the perfect c-axis orientation of the thin films, Ag-doping has been found to facilitate a remarkable decrease in the in-plane electrical resistivity. However, if doped beyond the substitution limit, excessive Ag was observed to severely reduce the Seebeck coefficient. Through carrier concentration adjustment by Ag-substitution, power factor of the Ag-Ca3Co4O9 thin films could reach 0.73 mW m−1 K−2 at around 700 K, which was about 16% higher than that of the pure Ca3Co4O9 thin film. 相似文献
12.
Pure and Pr6O11-doped CaCu3Ti4O12 (CCTO) ceramics were prepared by conventional solid-state reaction method. The compositions and structures were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influences of Pr-ion concentration on dielectric properties of CCTO were measured in the ranges of 60 Hz-3 MHz and 290-490 K. The third phase of Ca2CuO3 was observed from the XRD of CCTO ceramics. From SEM, the grain size was decreased obviously with high valence Pr-ion (mixing valence of Pr3+ and Pr4+) substituting Ca2+. The room temperature dielectric constant of Pr-doped CCTO ceramics, sintered at 1323 K, was an order of magnitude lower than the pure CCTO ceramics due to the grain size decreasing and Schottky potential increasing. The dielectric spectra of Pr-doped CCTO were flatter than that of pure CCTO. The loss tangent of Pr-doped CCTO ceramics was less than 0.20 in 2 × 102-105 Hz region below 440 K. The complex impedance spectra of pure and Pr-doped CCTOs were fitted by ZView. From low to high frequency, three semicircles were observed corresponding to three different conducting regions: electrode interface, grain boundary and grain. By fitting the resistors R and capacitors C, the activation energies of grain boundary and electrode contact were calculated. All doped CCTOs showed higher activation energies of grain boundary and electrode than those of pure CCTO ceramics, which were concordant with the decreasing of dielectric constant after Pr6O11 doping. 相似文献
13.
14.
Yih-Chien Chen Sheng-Kai YangKuang-Chiung Chang 《Journal of Alloys and Compounds》2011,509(39):9518-9522
The microwave dielectric properties of La(Mg0.5−xNixSn0.5)O3 ceramics were examined with a view to their exploitation for mobile communication. The La(Mg0.5−xNixSn0.5)O3 ceramics were prepared by the conventional solid-state method at various sintering temperatures. The X-ray diffraction patterns of the La(Mg0.4Ni0.1Sn0.5)O3 ceramics revealed no significant variation of phase with sintering temperatures. Apparent density of 6.71 g/cm3, dielectric constant (?r) of 20.19, quality factor (Q × f) of 74,600 GHz, and temperature coefficient of resonant frequency (τf) of −85 ppm/°C were obtained for La(Mg0.4Ni0.1Sn0.5)O3 ceramics that were sintered at 1550 °C for 4 h. 相似文献
15.
Zhongtian YangZhanqiang Liu Aihua FangFuqiang Huang Xiaoming Xie 《Journal of Alloys and Compounds》2011,509(6):2846-2849
The SmFe1−xCoxAsO (x = 0 − 0.25) superconductors were synthesized by mechanical alloying (MA) and rapid sintering method with Co atoms doped into FeAs layers to replace the Fe sites. The phase purity and superconducting properties of the samples were characterized by X-ray diffraction, electrical resistivity, magnetic susceptibility and Hall coefficient. All the samples belong to the tetragonal ZrCuSiAs structure type with the grain size in 1-3 μm. The superconducting critical temperature Tc of SmFe0.9Co0.1AsO was 12.5 K, and the structure/SDW transition was suppressed by Co doping. The negative Hall coefficient of SmFe0.9Co0.1AsO indicated the electron conduction in the sample. The charge carrier density is about 2 × 1020 cm−3 at the temperature lower than 150 K, larger than that of SmFeAsO. 相似文献
16.
H.D. ZhaoG.W. Qin Y.P. RenW.L. Pei D. ChenY. Guo 《Journal of Alloys and Compounds》2011,509(3):627-631
The solid solubility of Y in the α-Mg matrix and composition homogeneity ranges of Mg24Y5 − x and Mg2Y1 − x phases in the Mg-Y binary system are important parameters to understand solid-solution- and aging-strengthening effects of Mg-Y-based alloys. However, they are different among the various assessed Mg-Y phase diagrams which are based on limited experimental data, especially at temperatures below ∼850 K. Our experimental results by using both diffusion couple technique and alloy method are in good agreement each other, but much different from the presently accepted Mg-Y phase diagram. The results show that the maximum solubility of Y in the α-Mg matrix is 4.7 at.% Y, much larger than the current phase diagram. The determined composition homogeneity ranges of Mg24Y5 − x and Mg2Y1 − x phases are much wider than the present ones and shift remarkably to the Mg-rich corner of Mg-Y phase diagram. 相似文献
17.
Yuan-Bin Chen 《Journal of Alloys and Compounds》2011,509(24):6884-6888
The effects of BaCu(B2O5) additives on the sintering temperature and microwave dielectric properties of (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics were investigated. The (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics were not able to be sintered below 1000 °C. However, when BaCu(B2O5) were added, they were sintered below 1000 °C and had the good microwave dielectric properties. It was suggested that a liquid phase with the composition of BaCu(B2O5) was formed during the sintering and assisted the densification of the (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics at low temperature. BaCu(B2O5) powders were produced and used to reduce the sintering temperature of the (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics. Good microwave dielectric properties of Q × f = 35,000 GHz, ?r = 18.5.0 and τf = −51 ppm/°C were obtained for the (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics containing 7 wt.% mol% BaCu(B2O5) sintered at 950 °C for 4 h. 相似文献
18.
S.C. PrashanthaB.N. Lakshminarasappa B.M. Nagabhushana 《Journal of Alloys and Compounds》2011,509(42):10185-10189
Nanoparticles of Eu3+ doped Mg2SiO4 are prepared using low temperature solution combustion technique with metal nitrate as precursor and urea as fuel. The synthesized samples are calcined at 800 °C for 3 h. The Powder X-ray diffraction (PXRD) patterns of the sample reveled orthorhombic structure with α-phase. The crystallite size using Scherer's formula is found to be in the range 50-60 nm. The effect of Eu3+ on the luminescence characteristics of Mg2SiO4 is studied and the results are presented here. These phosphors exhibit bright red color upon excitation by 256 nm light and showed the characteristic emission of the Eu3+ ions. The electronic transition corresponding to 5D0 → 7F2 of Eu3+ ions (612 nm) is stronger than the magnetic dipole transition corresponding to 5D0 → 7F1 of Eu3+ ions (590 nm). Thermoluminescence (TL) characteristics of γ-rayed Mg2SiO4:Eu3+ phosphors are studied. Two prominent and well-resolved TL glows with peaks at 202 °C and 345 °C besides a shoulder with peak at ∼240 °C are observed. The trapping parameters-activation energy (E), order of kinetics (b) and frequency factor (s) are calculated using glow curve shape method and the results obtained are discussed. 相似文献
19.
B. Pato-DoldánM. Sánchez-Andújar S. Castro-García M.A. Señarís-Rodríguez 《Journal of Alloys and Compounds》2011,509(5):1529-1533
We have prepared polycrystalline single-phase ACo2+xRu4−xO11 (A = Sr, Ba; 0 ≤ x ≤ 0.5) using the ceramic method and we have studied their structure, electrical resistivity and Seebeck coefficient, in order to estimate their power factor (P.F.). These layered compounds show values of electrical resistivity of the order of 10−5 Ωm and their Seebeck coefficients are positive and range from 1 μV K−1 (T = 100 K) to 20 μV K−1 (T = 450 K). The maximum power factor at room temperature is displayed by BaCo2Ru4O11 (P.F.: 0.20 μW K−2 cm−1), value that is comparable to that shown by compounds such as SrRuO3 and Sr6Co5O15. 相似文献
20.
New compounds RuMn2Z (Z = Si, Sn) have been synthesized. X-ray diffraction measurements have confirmed that RuMn2Z (Z = Si, Sn) crystallizes in a Heusler-like cubic structure. The lattice parameters of RuMn2Si and RuMn2Sn at room temperature are estimated to be 5.8260 Å and 6.2195 Å, respectively. Magnetization measurements have been carried out in fields up to 50 kOe for RuMn2Z (Z = Si, Sn). Furthermore, the temperature dependence of initial permeability of RuMn2Sn has been studied. RuMn2Sn shows ferrimagnetic behavior. The spontaneous magnetic moment at 5 K and the Curie temperature of RuMn2Sn are found to be of 1.68 μB/f.u. and 272.1 K, respectively. RuMn2Si exhibits spin-glass-like behavior with a freezing temperature estimated to be about 50 K. 相似文献