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1.
较低的催化活性大大地限制了La0.85Sr0.15Cr0.9Ni0.1O3-δ-(LSCN)作为直接碳氢化合物燃料SOFC阳极材料的应用.本文尝试用Pechini法合成LSCN,并按重量比1:1向其中加入纳米Ce0.8Sm0.2O1.9(SDC)作为阳极材料.经1500℃高温烧结12h后,LSCN与SDC以及电解质YSZ仍可以保持各自独立的相结构.加入SDC没能提高阳极的电导率,但由于改善了阳极电解质界面的结合状况,扩展了电极反应的活性区域,使阳极材料的极化性能有了提高.显微结构观察品示.LSCN-SDC阳极存甲烷与氧中使用时没有碳沉积现象. 相似文献
2.
The magnetic behavior of La 0.85Sr 0.15CoO 3 single crystals and polycrystals has been subjected to a controversial debate for the last several years; while some groups show evidence for phase separation, others show spin-glass (SG) behavior. Here, we present a comprehensive investigation of the structural, ac susceptibility, and dc magnetization properties of La 0.85Sr 0.15CoO 3 single crystals grown by float zone method. The structural analysis of XRD data by Rietveld refinement reveals the single crystallographic phase. The ac susceptibility results exhibit a frequency dependent peak shift (??2 K) and time-dependent memory effect below the freezing temperature. The characteristic time scale ?? o calculated from this peak shift is found to be of ??10 ?13 s which matches very well with typical values observed for a SG system. Further, the peak shift of the zero-field-cooling curves to lower temperature at higher dc fields is well described by the well-known de Almeida Thouless line, a characteristic of SG behavior. Thus, all our experimental findings confirm the existence of SG behavior in La 0.85Sr 0.15CoO 3 single crystals. 相似文献
6.
In this paper, La 0.85K 0.15MnO 3 nanoparticles were successfully synthesized at relatively low calcinated temperature from a polyaminocarboxylate complex precursor with diethylenetriaminepentaacetic acid (H 5DTPA) as ligand, and the magnetocaloric properties were investigated . The phase transformation, chemical composition, and microstructure of La 0.85K 0.15MnO 3 nanoparticles were characterized by X-ray diffraction (XRD), thermogravimetric (TG), differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and electron diffraction (ED) . The results revealed that La 0.85K 0.15MnO 3 nanoparticles calcined at temperatures within the range of 600–1000 °C are of pure single-phase rhombohedral structure and the grain sizes were precisely controlled by varing the calcined temperature . The relationship between magnetocaloric properties and the calcined temperature of La 1?xK xMnO 3 nanoparticles was also investigated systematically . From the magnetic measurements as function of temperature and magnetic applied field, we have discovered that the Curie temperature TC is 274.5 K and is independent of the calcined temperature . From the measurements and calculation of isothermal magnetization at different temperatures, the maximum magneticentropy changes close to TC (274 K) of the samples calcined at 600 °C, 800 °C and 1000 °C are 2.02, 3.06 and 3.56/kg K at H = 2T, respectively. Also La 0.85K 0.15MnO 3 nanoparticle displays a second-order phase transition. These results suggest that this material is a candidate for use as an active for magnetic refrigerent around the room temperature. 相似文献
7.
The paper discuses synthesis of La 0.67Sr 0.33MnO 3 and BaZr 0.15Ti 0.85O 3 thin film heterostructures using modified Pechini method (citrate gel) and spin coating technique. The XRD spectra are determined for confirmation of the crystal structure and phase formation of thin film composites. The paper presents variation of real and imaginary parts of dielectric constant ε′, ε″ and tan δ as function of frequency between 100 Hz and 1 MHz and applied magnetic field up to 0.6 T. The paper, also discuses the effect of magnetic field on AC conductivity. The observed variation of magnetocapacitance and impedance spectra are analyzed in terms of a possible equivalent circuit model. The present analysis shows that the method of impedance spectra could be used to separate out the possible contributions to the magnetodielectric effect. 相似文献
8.
Abstracts are not published in this journal
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
11.
In this study, magnesium-cobalt ferrite (Mg0.85Co0.15Fe2O4) powder was synthesized using a solid-state synthesis method, followed by the liquid sintering using 0.50–3.00 wt% vanadium oxide (V2O5) at 1050 °C for 2 h. X-ray diffraction (XRD) studies confirmed the formation of spinel ferrite. Microstructure studies revealed that by increasing the amount of V2O5 from 0.50 to 3.00 wt%, the average grain size was reduced from 15.9?±?5.9 to 7.0?±?2.5 μm and the samples were highly densified. V2O5 promoted the sintering process and reduced the dielectric constant (ε′), loss tangent (tanδ), and increased electrical resistivity. A magnesium-cobalt ferrite sample with 25.4 dielectric constant, 0.078 loss tangent, and 9.0?×?105 Ω.cm resistivity at 1 MHz was achieved using 3.00 wt% V2O5. Increasing V2O5 content caused increasing coercivity (Hc) from 89 to 129 Oe. Moreover, the maximum saturation magnetization (Ms) value of 26.8 emu/g was obtained for the sample containing 1.50 wt% V2O5. The small dielectric loss tangent of the samples at 1 MHz suggests applications of these ceramics in microwave devices. 相似文献
12.
A novel preparation route to the perovskite materials Ca 0.3La 0.7CrO 3, Sr 0.16La 0.84CrO 3, and Sr 0.2La 0.8MnO 3 is described. The method produces the phase pure perovskite phases after calcination at 700°C for 2 hours. The powders produced are unagglomerated, and consist of hollow spherical particles 0.15 m in diameter. EDX has shown that the careful control of reaction conditions is vital to control the phase composition, and that small changes in stoichiometry result in the production of unsinterable powder. 相似文献
13.
We present a study of the effect of Ga-doping on the physical properties of La 0.75Ca 0.1Sr 0.15Mn 1?x Ga x O 3 ( x=0.025, 0.075 and 0.1) compounds prepared by the sol-gel method. The variation of the magnetization ( M) vs. temperature ( T), under an applied magnetic field of 0.05 T, reveals a ferromagnetic–paramagnetic transition for all samples. The magnetization behavior and the Curie temperature T C have shown a large dependence on the fractional composition x. In fact, the M( T) curves have revealed the presence of a long-range ferromagnetic state below T C. The magnetotransport properties have been investigated based on the temperature dependence of the resistivity ρ( T) measurements. We have noted that these samples present an electrical transition from a paramagnetic-semiconductor state to a ferromagnetic-metallic one, when decreasing temperature. We have used the phenomenological equation for conductivity under a percolation approach, which is based upon an approach that the system consists of the phase separated ferromagnetic metallic and paramagnetic insulating regions. We have then fitted the resistivity data measured in the range of 15–300 K and found that the activation barrier decreases with the raising Ga 3+ ion concentration. 相似文献
14.
Ba0.85Ca0.15Zr0.1Ti0.9O3/La0.7Sr0.3MnO3 (BCZT/LSMO) bilayer multiferroic heterostructures with different BCZT layer thickness are fabricated by pulsed laser deposition technique. Structural characterization of XRD and TEM reveals the epitaxial growth of the bilayer heterostructures, whose residual strain reduces with increasing thickness. The room temperature multiferroic characteristics of the bilayer heterostructures are demonstrated by the simultaneously observed ferroelectric and ferromagnetic properties as well as the magnetoelectric effect. Due to the varying residual strain, the multiferroic properties of the bilayer heterostructures show strong dependence on the BCZT layer thickness, which significantly improves with increasing thickness. The largest magnetoelectric coefficient with αE31 value of 355.2 mV/cm·Oe is achieved in BCZT/LSMO bilayer heterostructures with BCZT layer thickness of 150 nm. 相似文献
15.
用高分子凝胶法制备了氧化物固体电解质SrCeo.85Yo.15O2.925,研究了单体与网络剂的配比、烧结温度等参数对相平衡关系和材料性能的影响.结果表明:当单体与网络剂的质量比是5:1,在1300℃烧结可以合成出单相钙钛矿结构的SrCeo.85Yo.15O2.925.样品的致密性随着烧结温度的升高而提高,在1300℃烧结出的样品密度大约为理论密度的95%;电导率随着样品密度的增大而增大,700℃时样品的电导率大于0.10 mS·m-1. 相似文献
17.
Journal of Materials Science: Materials in Electronics - Pb0.85La0.1(Zr0.85Ti0.15)O3 (PLZT) antiferroelectric (AFE) thin films with different thicknesses were prepared by the sol–gel method... 相似文献
18.
Samples of La 1.85Sr 0.15Cu 1-xM xO y(M = Ni, Zn, and Mg) with a wide range of dopant concentration (0≤ x≤0.30) were synthesized. X-ray diffraction analysis shows that the Zn doping results in a tetragonal-orthorhombic transition
as x- >0.15. while both Ni- and Mg-doped samples still remain tetragonal up to x = 0.3. Furthermore, the Ni, Zn, and Mg dopings all reduce the local Jahn -Teller distortion of the CuO 6 octahedron in a similar way. The metalinsulator transition at the region of higher doping levei ( x> 0.1) is observed in all three doped systems. The observed metal-insulator transition can be well interpreted in the context
of Anderson’s theory of disorder-induced localization. For most of the semiconducting-like samples with higher doping level
(x> 0.1), the conductive behavior is dominated by two-dimensional variable-range-hopping (2D-VRH) with {ie-13-01} This suggests
that all the dopings of Ni, Zn, and Mg in Cu sites cause the localization of the holes. In addition, a remarkable difference
in the room-temperature resistivity for the heavily doped samples with the same dopant (Zn, Ni, Mg) concentrations is also
observed. A possible explanation is provided for this phenomenon. 相似文献
19.
The reactions between Sr and Mg substituted LaGaO 3, Sr substituted LaMnO 3, Ca substituted LaCrO 3, and Ni annealed at 650 and 1000°C for up to 1000 h have been studied. The experiments show that solid state reactions between the original phases occur forming additional compounds, for example LaSrGa 3O 7, LaSrGaO 4, La 4Ga 2O 9, and Ca 2Ga 2O 5. In addition, the chemical composition of LaGaO 3 changes during the heat treatments. At 650°C significant solubility of Cr and Ca in LaGaO 3 have been observed. The solid solubility of Mn and Ni in LaGaO 3 is moderate. 相似文献
20.
Sulfonated polymers have found use as ion-exchange membranes for use in fuel cells, water purification, electroactive devices, and inorganic materials templating and synthesis. Improving the materials for these applications and opening up new applications requires the ability to synthesis targeted or more complex sulfonated polymers, which includes tailoring the chemistry (copolymerization across a wider range of solubility) and/or polymer architecture (block, graft, nanoparticle). This article will summarize the recent work using sulfonated monomers with substituted ammonium counterions as a versatile route for enabling this goal. Two main benefits of these monomers are as follows. First, they are useful for preparing amphiphilic copolymers, which is a challenge using traditional acidic or alkali salt forms of sulfonated monomers. Second, sulfonated polymers with substituted ammonium counterions are useful polymers for obtaining unique material properties, such as organo-gelation of low polarity solvents or obtaining ionic liquid polymers for the fabrication of solid polymer electrolytes. 相似文献
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