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Oxygen ion conductivity of Lao.sSro.2Gao.s3Mgo.17-xCoxO3-δ synthesized by laser rapid solidification 下载免费PDF全文
Materials Lao.8Sro.2Gao.83Mgo.17_xCox03_6 with x = 0, 0.05, 0.085, 0.10, and 0.15 are synthesized by laser rapid solidification. It is shown that the samples prepared by laser rapid solidification give rise to unique spear-like or leaf-like microstructures which are orderly arranged and densely packed. Their electrical properties each show a general depen dence of the Co content and the total conductivities of Lao.8Sro.2Gao.83Mgo.085Coo.08503_6 prepared by laser rapid solidification are measured to be 0.067, 0.124, and 0.202 S.cm-1 at 600, 700, and 800 ℃, respectively, which are much higher than by conventional solid state reactions. Moreover, the electrical conductivities each as a function of the oxy gen partial pressure are also measured. It is shown that the samples with the Co content values 〈 8.5 mol% each exhibit basically ionic conduction while those for Co content values 〉 10 mol % each show ionic mixed electronic conduction under oxygen partial pressures from 10-16 atm (1 atm = 1.01325 x 105 Pa) to 0.98 atm. The improved ionic conductivity of Lao.sSro.2Gao.83Mgo.085Coo.08503 prepared by laser rapid solidification compared with by solid state reactions is attributed to the unique microstructure of the sample generated during laser rapid solidification. 相似文献
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We have determined kex and Dchem for (La0.8Sr0.2)0.99Co0.8Ni0.2O3-δ by the use of electrical conductivity relaxation on a dense sample and by applying the ALS model to measured AC impedance spectrum on a porous electrode. Extracting kex and Dchem from the methods resulted in comparable values. kex and Dchem also agreed well with literature values on La0.8Sr0.2CoO3-δ, indicating that nickel substitution does not change the oxygen transport properties. kex of the porous sample was further found to decrease with a five times higher rate than Dchem when measured by using an Electrochemical Impedance Spectroscopy (EIS) over several days. 相似文献
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采用溶胶 凝胶法制备了系列La0 .8-xCa0 .2 MnO3 多晶样品 ,用X射线衍射分析确定了样品的钙钛矿结构 ,用透射电子显微镜观察了样品的形貌及粒径分布情况 ,用PAR15 5型振动样品磁强计测量了样品的磁性随外场和温度的变化 ,确定样品的居里温度并计算了各样品的磁熵变 .磁测量及计算结果表明制备的各样品的居里温度在180— 2 6 0K的范围内且随焙烧温度和La3 离子空位浓度的不同而变化 ,不同温度焙烧的样品均有较大的磁熵变值 ,其中 110 0℃焙烧的La0 77Ca0 .2 MnO3,多晶样品在 2 40 5K ,H =1 0T的外场下的磁熵变达 3 76J/kg·K ,对实验结果做了定性的分析 .该材料具有较高的居里温度和较大的磁熵变 ,所需外场强度适中 ,电阻率高 ,性能稳定 ,适合做高温磁制冷材料 . 相似文献
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《中国物理 B》2015,(5)
Ag-doped manganite powder samples, La0.7Sr0.1AgxMnO3-δ(x = 0.00, 0.025, 0.05, 0.075, and 0.10) were synthesized using the sol–gel method. X-ray diffraction patterns indicated that the samples had two phases with the R3c perovskite being the dominant phase and Mn3O4 being the second phase. X-ray energy dispersive spectra indicated that the ratio of Ag to La was very close to that of the nominal composition in the samples. The specific saturation magnetizations at 300 K increased from 32.0 A·m2/kg when x = 0.00 to 46.8 A·m2/kg when x = 0.10. The Curie temperature, T C, of the samples increased from 310 K when x = 0.00 to 328 K when x = 0.10. Because the atomic concentration ratios of La, Sr, and Mn in the five samples were all the same and only the Ag concentration changed, the variations of the specific saturation magnetizations at 300 K and the Curie temperatures suggested that the Ag cations have been doped into the A sites of the perovskite phase in the samples. 相似文献
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Spin glassy behavior and large exchange bias effect in cubic perovskite Ba_(0.8)Sr_(0.2)FeO_(3-δ) 下载免费PDF全文
《中国物理 B》2019,(6)
A single-phase iron oxideBa_(0.8)Sr_(0.2)FeO_(3-δ)with a simple cubic perovskite structure in Pm-3 m symmetry is successfully synthesized by a solid-state reaction method in O_2 flow. The oxygen content is determined to be about 2.81, indicating the formation of mixed Fe~(3+)and Fe~(4+)charge states with a disorder fashion. As a result, the compound shows small-polaron conductivity behavior, as well as spin glassy features arising from the competition between the ferromagnetic interaction and the antiferromagnetic interaction. Moreover, the competing interactions also give rise to a remarkable exchange bias effect in Ba_(0.8 )Sr_(0.2 )FeO_(2.81), providing an opportunity to use it in spin devices. 相似文献
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采用溶胶-凝胶法制备了双稀土掺杂氧化铈Ce_(0.8)Pr_(0.2-x)Nd_xO_(2-δ)(x=0.02,0.05,0.1)固溶体。X射线衍射分析阐明,经800℃烧结的全部固溶体都形成了单相立方萤石结构,平均晶粒尺寸在20~25 nm之间。拉曼光谱结果阐明,固溶体Ce_(0.8)Pr_(0.2-x)Nd_xO_(2-δ)是具有氧空位的立方萤石结构,适量的掺杂Nd有利于Ce_(0.8)Pr_(0.2-x)Nd_xO_(2-δ)氧空位浓度的增加。阻抗谱结果阐明,稀土双掺杂的Ce_(0.8)Pr_(0.2-x)Nd_xO_(2-δ)比稀土单掺杂的Ce_(0.83)Sm_(0.17)O_(2-y)的电导率高,Ce_(0.8)Pr_(0.18)Nd_(0.02)O_(2-δ)的电导率最大,600℃时电导率为1.85×10~(-2)S/cm。 相似文献
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Li YK Shen CY Guo HJ Lv C Yang XJ Zhang L Luo YK Cao GH Xu ZA 《J Phys Condens Matter》2012,24(23):232202
A series of K(0.8)Fe(2-δ-x)Zn(x)Se(2) single-crystal samples with nominal compositions 0?≤?x?≤?0.05 were grown and their physical properties were measured in order to study the effect of Zn impurity. It is found that the Zn impurity (x?≤?0.02) does not affect the superconducting transition temperature T(c) significantly. Meanwhile the hump in resistivity which corresponds to the transition from the insulating to metallic phase quickly shifts towards low temperatures. The results imply that there should be a phase separation in this system and Zn impurity causes the enhancement of the insulating phase. The negligible effect of Zn impurity on T(c) suggests an s-wave pairing in the superconducting phase. Meanwhile there is a possibility that the Zn impurity may selectively enter into the insulting phase. 相似文献
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采用传统固相反应法制备钙钛矿型锰氧化物(La0.8Eu0.2)4/3Sr5/3Mn2O7多晶样品,X-射线衍射分析表明,样品(La0.8Eu0.2)4/3Sr5/3Mn2O7结构呈现良好的单相.通过磁化强度随温度的变化曲线(M-T)、不同温度下磁化强度随磁场的变化曲线(M-H)和电子自旋共振谱发现:在300 K以下,随着温度的降低,样品先后经历了二维短程铁磁有序转变(T2D C≈282K)、三维长程铁磁有序转变(T3D C≈259K)、奈尔转变(T N≈208K)和电荷有序转变(T CO≈35K);样品(La0.8Eu0.2)4/3Sr5/3Mn2O7在T N以下,主要处于反铁磁态;在T3D C达到370 K时,样品处于铁磁-顺磁共存态,在370 K以上时样品进入顺磁态.此外,分析电阻率随温度的变化曲线(ρ-T)得到:样品在金属-绝缘转变温度(T P≈80K)附近出现最大磁电阻值,其位置远离T3D C,表现出非本征磁电阻现象,其磁电阻值约为61%.在T CO以下,电阻率出现明显增长,这是由于温度下降使原本在高温部分巡游的e g电子开始自发局域化增强所致.通过对(La0.8Eu0.2)4/3Sr5/3Mn2O7的ρ-T曲线拟合,发现样品在高温部分的导电方式基本遵循小极化子的导电方式. 相似文献
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Oxygen permeation measurements were carried out on La0.8Sr0.2Ga0.75Mg0.15Co0.10O3±δ specimens of different thickness at temperatures between 673 and 1173 K under various gradients of oxygen partial pressure. Simultaneously, the open circuit cell voltage was measured. It was shown that the investigated compositions were characterized by a high oxygen permeation rate, and, consequently, by a high electronic conductivity. The electrode polarization effect was experimentally proved, and the influence of the measurement conditions on the degree of the electrode polarization effect was studied and discussed in detail. In particular, this mentioned influence was found to be sufficiently smaller at higher oxygen partial pressures in the cathode (oxygen-rich) compartment, while the change of pO2 on the anode (oxygen-lean) side of the permeation cell did not lead to any sufficient electrode polarization. The values of the hole conductivity calculated from the experimental results found to be at least influenced by electrode polarization were used for calculations of the hole conductivity. The comparison of these values with results obtained by other experimental techniques (by pO2-dependence of the total conductivity measured using impedance spectroscopy and Hebb–Wagner-polarization technique) demonstrated a satisfactory agreement. 相似文献
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M. Smirnov S. Sukhomlinov A. Mirgorodsky O. Masson E. Bchade M. Colas T. Merle‐Mjean I. Julien P. Thomas 《Journal of Raman spectroscopy : JRS》2010,41(12):1700-1707
Vibrational spectroscopy data were used to gain insight into the possible locations of extra oxygen ions introduced into La8+xSr2−y(SiO4)6O2+δ compounds to raise their ionic conductivity. Perturbations observed in the Raman and infrared spectra of these compounds with increasing δ were explained by using the ab initio calculation results for the fully stoichiometric (x = y = δ = 0) lattice. This allowed the inference that the extra oxygen ions are incorporated into La O tunnel‐like fragments inherent in the studied structures. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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A. A. Yaremchenko V. V. Kharton A. P. Viskup E. N. Naumovich V. N. Tikhonovich N. M. Lapchuk 《Solid State Ionics》1999,120(1-4):65-74
The LaGa1−x−yCoxMgyO3−δ solid solutions with rhombohedrally-distorted perovskite structure were ascertained to form in the concentration range of 0≤y≤0.10 at x=0.60 and 0≤y≤0.20 at x=0.35–0.40. Increasing cobalt content results in increasing electrical conductivity and thermal expansion of the perovskites. Thermal expansion coefficients of the LaGa1−x−yCoxMgyO3−δ ceramics were calculated from the dilatometric data to vary in the range of 12.4–19.8×10−6 K−1 at 300–1100 K. Doping La(Ga,Co)O3−δ solid solutions with magnesium leads to increasing oxygen nonstoichiometry, electronic and oxygen ionic conductivity. Oxygen permeation fluxes through LaGa1−x−yCoxMgyO3−δ membranes were found to be limited by the bulk ionic conduction and to increase with magnesium concentration, being essentially independent of cobalt content. 相似文献