共查询到20条相似文献,搜索用时 31 毫秒
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By measuring M-T curves, ρ-T curves and MR-T curves of the samples under different temperatures, the influence of Dy doping (0.00 ≤ x ≤0.30) on the magnetic and electric properties of La0.7-xDyxSr0.3MnO3 has been studied. The experimental results show that, with the increase of the Dy content, the system undergoes a transition from long range ferromagnetic order to the cluster-spin glass state and further to antiferromagnetic order. For the samples with x=0.20 and 0.30, their magnetic behaviors are abnormal at low temperature, and their resistivities at low temperature have a minimum value. These peculiar phenomena not only come from the lattice effect induced by doping, but also from extra magnetic coupling induced by doping. 相似文献
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在氧离子导体La2Mo1.7W0.3O9的基础上,采用固相法合成了La位掺杂的Ca系列新型氧化物La2-xCaxMo1.7W0.3O9-δ(0≤x≤0.2)。通过XRD、Raman和XPS等手段对化合物结构进行表征,交流阻抗谱测试其电性能。结果表明:掺杂离子Ca2+的半径小于基质离子La3+的半径导致晶格收缩;Ca的掺杂在La2Mo1.7W0.3O9自身内置氧空位的基础上增加了额外的氧空位,提高了氧离子导体的电导率,550 ℃电导率由0.79 × 10-4 S·cm-1 (x=0.0)增加到1.5 × 10-4 S·cm-1 (x=0.16,0.2),电导率增加89.9%。 相似文献
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使用复杂晶体化学键理论计算了La1-xNdxCrO3 (x =0 .0 ,0 .2 ,0 .4,0 .6 ,0 .8,1.0 )的化学键参数 ,如键性、键极化率等。结果表明 ,La-O ,Nd -O和Cr-O键的共价性基本上不随Nd掺杂的变化而变化 ,这个结论与实验结果一致。键极化率和磁距则随着掺杂量的增加而增加。共价性的大小次序为La -O 相似文献
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Chen Ximeng Wang Qiang Liu Zhaoyuan Cai Xiaohong Ma Shuxun Zhang Hualin 《Journal of Radioanalytical and Nuclear Chemistry》2003,258(1):189-190
The K X-ray relative transition probabilities Kb/Ka of some elements for atomic numbers 23Z33 induced by 3 MeV protons were measured. The experimental results are compared with the relativistic Hartree-Fock (RHF) calculations. Good agreements have been obtained considering the experimental error. 相似文献
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采用柠檬酸法合成了一系列含Ce的La1-xCexSrNiO4,发现Ce在A位的取代量能够达到30%.大量Ce取代La后,不仅改善了无氧条件下对NO分解的活性,还提高了LaSrNiO4在有氧条件下的催化活性.在体积分数为6.0%的O2存在下,La0.7Ce0.3SrNiO4对NO分解比活性高达1.58 μmol/(s·m2)(1 123 K),表明La1-xCexSrNiO4是一种很有潜力的NO消除催化剂. 相似文献
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LiNi0.3Co0.7O2的结构及其锂电池行为的研究 总被引:4,自引:0,他引:4
章福平 《高等学校化学学报》1995,16(5):770-774
利用XRD、XPS、CV等方法研究了LiNi0.3Co0.7O2的结构及其锂电池行为。结果表明:LiNi0.3Co0.7O2具有六方晶系空间群结构,其晶胞参数a=0.2826nm,c=1.4130nm;其表面存在Li2O;Li+在其中的化学扩散系数为1~7×10-8cm2·s-1;其锂电池在4.30~3.00V间放电容量可达120~140mA·h·g-1,放电机理为Li+在其中进行两步嵌入反应。 相似文献
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The M emission spectra of the elements 55 Cs, 56 Ba, 57 La, and 58 Ce were measured using wavelength dispersive X-ray spectrometry with a TAP crystal as the dispersing element. In total, 34M lines were observed, of which only 13 are contained in the compilation of Bearden. M and M of 56 Ba are among the new lines. They have their origin in a similar process to one that is known for 57 La. The interpretation of these spectra is complicated by the strong overlap of some emission lines with the MIV,V absorption structures, which may lead to anomalous self-absorption effects. Therefore, we have concentrated on spectra taken at a low energy of the exciting electrons, E0=2.5keV. However, in order to illustrate the anomalous self-absorption effects parts of the 2.5keV spectra, of Ba and La, are shown in comparison with the 10keV spectra. 相似文献
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As part of our systematic research on the acentric rare earth chalcogenides, the ErAlGeS5/KBr, Er3AgGeS7/KBr and Er6Ge3S14/KBr systems were investigated and three compounds belonging to the R6B2C2Q14 (R = rare earth, B = 6-coordinated element, C = 4-coordinated element, Q = S and Se) family were identified. These compounds crystallize in the P63 space group, and the crystal data are as follows: Er3Ge1/4GeS7, a = 9.6480(14), c = 5.7920(12) A^°, Z = 2; Er3Ge0.382(8)GeS7, a = 9.6360(14), c = 5.8460(12) A^°, Z = 2; Er3Ge1/2GeS7, a = 9.6061(13), c = 5.8346(18)A^°, Z = 2. Single-crystal analysis indicated that the Er3GexGeS7 (x = 1/4, 0.382(8), 1/2) structures consist of three types of building blocks: ErS7, GeS4 and GeS6 units. Er3MxGeS7 are deficient compounds with the B sites occupied partly by Ge(Ⅳ) and/or Ge(Ⅱ). 相似文献
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采用真空电弧熔炼法制备了LaN i3.8-xA lx(0≤x≤0.5)储氢合金,并在氩气气氛中进行退火处理。通过X射线衍射(XRD),S ievert′s方法和电化学测试分别分析了合金的物相结构、储氢和电化学性能。研究结果表明:LaN i3.8-xA lx(0≤x≤0.5)合金主要由LaN i5,Ce2N i7,Pr5Co19和Ce5Co19型相组成。随着A l的变化,各相相丰度发生变化,而相丰度的变化影响了合金的滞后和吸/放氢平台压力。随着x的增加,LaN i3.8-xA lx(0≤x≤0.5)合金的放电容量先增大至270 mAh.g-1(x=0.3),然后缓慢降低;在x=0.3时合金显示出较好的充/放电循环稳定性。极化电阻和电化学交流阻抗则随着x的增加缓慢降低,交换电流密度增大,导致高倍率放电有所增大。 相似文献
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采用高温固相反应法制备了质子导体BaCe0.8-xNbxGd0.2O3-δ(0≤x≤0.45)。结合XRD、SEM、EIS等技术对其物相、微观形貌、稳定性及电导率进行了研究。结果表明,在1 600 ℃烧结5 h制备的质子导体BaCe0.8-xNbxGd0.2O3-δ(0≤x≤0.45)均能保持主相为斜方晶的钙钛矿结构。Nb的加入可明显提高烧结样品的致密性及在CO2和水蒸气气氛下的稳定性。在湿润H2/Ar(0.4%,V/V)气氛中800 ℃下,x=0.1样品的电导率为5.73 mS·cm-1,电导活化能为0.35 eV,与x=0的样品相当。 相似文献
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将Se固溶复合到链状小硫分子S2~4中,利用超微孔碳(UMC)的空间限域效应,在UMC中成功构建了链状SemSn(2≤m+n≤4)小分子,并用作锂硫(Li-S)电池正极材料。与链状S2~4小分子相比,改性后的SemSn(2≤m+n≤4)小分子电导率更高,锂化能更低,放电锂化过程更容易。所制得的UMC/SemSn(2≤m+n≤4)复合正极材料的放电过程为一步固相转化反应,从而有效抑制了活性物质的穿梭流失。与UMC/S2~4复合正极材料相比,UMC/SemSn(2≤m+n≤4)复合正极材料的电荷传递阻抗更小,放电比容量更高。因此,UMC/SemSn-40(2≤m+n≤4,wSeS2∶wUMC=4∶6)复合正极材料在0.1C时循环100次后,比容量依然保持有844 mAh·g-1;在0.5C下长时间循环500次时,每次循环容量损失仅约为0.07%,表现出优异的循环稳定性。 相似文献
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新型锂离子电池阳极材料Li2.7Mg0.3N的研究 总被引:1,自引:0,他引:1
以氮化锂和镁金属为原料,制备了Li2.7Mg0.3N样品,利用XRD、原子吸收、库仑滴定等方法研究了锂离子电池阳极材料Li2.7Mg0.3N的组成、结构及电化学性能。样品Li2.7Mg0.3N经成分分析组成为Li2.74Mg0.26N;其结构为四方晶系,晶胞参数a=0.388nm,c=0.547nm;比容量为1695(mA.h)/g,嵌入量x最大可达2.5276,室温时锂离子嵌入Li2.7Mg0.3N的嵌入自由能为-397.51kJ/mol,锂离子在Li2.7Mg0.3N中的化学扩散系数为5.90×10^-^11~7.23×10^-^10cm^2/s,并得到一系列热力学和动力学参数。 相似文献
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Configuration of the surface atoms in aluminum clusters was investigated based on the structures with global minimum potential energy of some Al clusters in the size range of 270-500. The structures were optimized by the dynamic lattice searching with constructed cores (DLSc) method with the NP-B potential. In the optimized structures, all clusters are identified as truncated octahedra (TO) including three complete TO at Al(260), Al(314), and Al(405). With the model of TO(260) and TO(405), the configurations of the surface atoms in the structures of the clusters from 261 to 314 and from 406 to 459 were investigated. The sites on (100) faces are found to be preferable to those on (111) faces for locating the new atoms with the increase of the cluster size, but for the clusters larger than 405 atoms, the sites on the (111) face are favored when the number of atoms exceeds the site number of a (100) face. Furthermore, the sites on the edge adjoining a (100) face and a (111) face are found to be very important to make a cluster more stable. 相似文献