共查询到19条相似文献,搜索用时 93 毫秒
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本文用差热分析法和高温、室温X射线衍射法对Li3VO4,Li4SiO4的相变过程,Li3VO4-Li4SiO4,Li3O4-Li-4GeO4赝二元系相图以及Li3VO4-Li4SiO4-Li4GeO4赝三元系相图室温截面进行了研究。发现在Li3VO4-Li4SiO4,Li3VO4-Li4GeO4赝二元系中,由于Li4SiO4或Li4GeO4的加入而使Li3VO4的高温γII相稳定存在于室温,从而得到一种新的具有高电导率的锂离子导体。作者认为探寻使高温态稳定存在于室温的方法是探索新的离子导体研究中有效途径之一。
关键词: 相似文献
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本文用X射线和差热分析方法对BaO-Li2O-B2O3三元系中的两个截面:BaB2O4-Li2B2O4和BaB2O4-Li2O作了研究。在BaB2O4-Li2B2O4赝二元系中发现了一个新的化合物4BaB2O4·Li2B2O4。化合物在930±3℃由包晶反应形成,并与Li2B2O4形成共晶反应。共晶温度为797±3℃,共晶点组分为79mol%Li2B2O4。在BaB2O4-Li2O截面中也存在化合物4BaB2O4·Li2B2O4,其包晶反应温度从930±3℃随Li2O含量增加下降到908±3℃。在组分60mol%Li2O处形成另一个新的化合物2BaB2O4·3Li2O。该化合物在630±3℃也是由包晶反应形成,并与Li2O和Li2CO3分别形成共晶反应,共晶温度分别为400±3℃和612±3℃。在BaB2O4-Li2B2O4和BaB2O4-Li2O体系中都没有观察到固溶体。用计算机程序分别对化合物4BaB2O4·Li2B2O4和2BaB2O4·3Li2O的X射线粉末衍射图案进行了指标化,其结果:4BaB2O4·Li2B2O4的空间群为Pmma,a=13.033?,b=14.630?,c=4.247?,每个单胞包含两个化合式单位;2BaB2O4·3Li2O的空间群为Pmmm,a=4.814?,b=9.897?,c=11.523?,每个单胞也含有两个化合式单位。
关键词: 相似文献
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采用脉冲激光沉积技术制备了Ti/Pr0.7Ca0.3MnO3/Pt和Ti/Pr0.7Ca0.3MnO3/La0.67Sr0.33MnO3/Pt异质结并研究了La0.67Sr0.33MnO3功能插层对异质结电致电阻特性的影响. 实验结果表明La0.67Sr0.33MnO3功能层的引入有效提高了器件的电阻转变特性,尤其是电阻转变率和疲劳性得到了极大的改善. 对La0.67Sr0.33MnO3插层改善电致电阻转变特性的机理进行了定性的分析.
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电致电阻效应
电阻转变比率
疲劳特性 相似文献
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研究了三种掺Yb钒酸盐混晶Yb0.005:Y0.298Gd0.697VO4, Yb0.007:Y0.407Gd0.586VO4和Yb0.009:Y0.575Gd0.416VO4的室温偏振吸收谱和发射谱. 结果表明,最强的吸收和发射相应于π偏振,位
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掺Yb钒酸盐混晶
吸收谱和发射谱
激光振荡
偏振态 相似文献
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本文用X射线衍射、热处理及差热分析等方法测定了SrNb2O6-NaNbO3-LiNbO3赝三元系的室温截面及相应的SrNb2O6-NaNbO3,SrNb2O6-LiNbO3和NaNbO3-LiNbO3等三个赝二元系相图;粗略地研究了Sr0.42Na0.16NbO3-LiNbO3系的纵截面;含5mol%LiNbO3及10mol%LiNbO3的SrNb2O6-NaNbO3的纵截面。确定了室温Sr2Na(NbO3)5(以下略为S2N)相为四方钨青铜结构。其点阵常数为a=12.36?,c=3.906?.LiNbO3在S2N相内的溶解度可达~10mol%,当LiNbO3含量超过5mol%时,S2N相畸变为S2N′相。S2N′相为正交晶系。实验确定室温S2N(S2N′)相系亚稳相。在900-1100℃长时间退火即分解为SrNb2O6和以NaNbO3为基的固溶体的混合物。
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结合机械合金化与放电等离子烧结工艺制备了Ni和Se共掺的细晶方钴矿化合物Co1-xNixSb3-ySey,研究了晶界和点缺陷的耦合散射效应对CoSb3热电输运特性的影响.通过Ni掺杂优化载流子浓度提高功率因子.在x=0.1时,功率因子达到最大值1750μWm-1K-2(450℃),是没有掺Ni试样的两倍.晶界和点缺陷的耦合散射机理使晶格热导率急剧下降,其中Co0.9Ni0.1Sb2.85Se0.15的室温晶格热导率降低至1.67Wm-1K-1,接近目前单填充效应所能达到的最低值1.6Wm-1K-1,其热电优值ZT在450℃时达到最大值0.53.将Callaway-Von Baeyer点缺陷散射模型嵌入到Nan-Birringer有效介质理论模型,对晶界散射和点缺陷散射的耦合效应对热导率的影响进行了定量分析,模型计算与实验结果符合.理论模型计算表明,当晶粒尺寸下降到50nm同时掺杂引入点缺陷散射后,Co0.9Ni0.1Sb2.85Se0.15的晶格热导率下降到0.8Wm-1K-1.
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3')" href="#">CoSb3
Ni和Se掺杂
热电性能
耦合散射效应 相似文献
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K.V. Ivanovskikh A. Meijerink A. Speghini C. Ronda M. Bettinelli 《Journal of luminescence》2010,130(5):893-16384
The silicates Ca3Sc2Si3O12, Ca3Y2Si3O12 and Ca3Lu2Si3O12, both undoped and doped with Pr3+ ions, have been synthesized by solid-state reaction at high temperature. The luminescence spectroscopy and the excited state dynamics of the materials have been studied upon VUV and X-ray excitation using synchrotron radiation. All doped samples have shown efficient 5d-4f emission upon direct VUV excitation of 5d levels, but only Ca3Sc2Si3O12:Pr3+ shows luminescence upon interband VUV or X-ray excitation. The VUV excited emission spectra of Ca3Y2Si3O12:Pr3+ and Ca3Lu2Si3O12:Pr3+ show features attributed to emission from two distinct sites accommodating the Pr3+ dopant. The decay kinetics of the Pr3+ 5d-4f emission in Ca3Sc2Si3O12:Pr3+ upon VUV excitation across the band gap are characterized by decay times in the range 25-28 ns with no significant rise after the excitation pulse. They appear to be faster upon X-ray irradiation than for VUV excitation. Weak afterglow components are attributed to defect luminescence. 相似文献
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采用磁控溅射,紫外线光刻和离子束刻蚀制备了La2/3Ca1/3MnO3/Eu2CuO4/La2/3Ca1/3MnO3磁性隧道结.通过对获得的磁性隧道结的I-V特性测量,发现非线性的I-V特性,显示结样品的隧穿特性.有趣的是发现在电极材料La2/3Ca1/3MnO3的金属-绝缘体转变温度(Tp)以下,I-V曲线出现一个跳变.随着温度降低,开始出现跳变的临界电流增大,但是跳变都发生在同样的电压下~209mV.当电流增大或减小在跳变点附近出现回滞.这一跳变只发生在铁磁金属态,表明这是一个磁性相关联的效应,可能对应一种新的磁性开关过程.虽然,目前对这一现象背后的物理机理还不清楚,但是,这一现象有可能在未来自旋电子学器件方面具有潜在的应用价值.
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庞磁电阻
磁性隧道结
开关效应 相似文献
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The effects of Nd-doping on the transport and magnetic properties of La2/3−yNdySr1/3MnO3 (y=0, 1/3, 2/3) are studied theoretically by using the generalized-gradient-corrected full-potential method. In order to investigate the coupling between Nd and Mn, the electronic structures of La2/3−yNdySr1/3MnO3 with ferromagnetic (FM) and antiferromagnetic (AFM) arrangements of Nd and Mn sublattices are calculated. The calculation for FM La2/3−yNdySr1/3MnO3 yields a half-metallic band structure, while the ferrimagnetic (FiM) system is found to have a metallic character. Hybridization of Nd 4f, Mn 3d, and O 2p bands around Fermi level (EF) is observed, suggesting the coupling between Nd and Mn is mediated by O 2p carriers. The qualitative features of transport and magnetic properties of such a two-spin system can be interpreted in terms of half-metallic FM domains being mixed up with metallic FiM domains. The proportion of FM domains varying with Nd-doping concentration has strong influences on the magnetoresistance. 相似文献
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El?bieta Jartych Mariusz Mazurek Dionizy Czekaj 《Journal of magnetism and magnetic materials》2010,322(1):51-55
X-ray diffraction and Mössbauer spectroscopy were applied as complementary methods to investigate the structure and hyperfine interactions in the series of Bim+1Ti3Fem−3O3m+3 Aurivillius compounds with m=4, 6, 7 and 8. Samples were synthesized by the solid-state sintering method at various temperatures. As X-ray diffraction analysis proved, the compounds formed single phases at temperature above 993 K. Mössbauer studies have confirmed diffraction measurements. Compounds synthesized at 993 K contained residual hematite, however these sintered at elevated temperatures were single-phased materials. Room-temperature Mössbauer spectra of Bim+1Ti3Fem−3O3m+3 compounds revealed their paramagnetic properties, what is consistent with the literature data concerning the Néel temperature of these ceramics (TN is smaller than room temperature). Detailed analysis of MS spectra allowed to state that iron ions may occupy both tetrahedral and octahedral sites in the crystallographic lattice of Aurivillius compounds. 相似文献
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A comparative study of phase transition in six compounds: K3MoO3F3, K3WO3F3, Rb3MoO3F3, Rb3WO3F3, Cs3MoO3F3 and Cs3WO3F3 was performed. All of them exhibit two transitions. One, at lower temperatures is possibly due to short range order-disorder phenomena in the anion octahedra, the second one is of a ferroelectric-paraelectric type. 相似文献
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Yong Joon Park Min Gyu KimYoung-Sik Hong Xianglan WuKwang Sun Ryu Soon Ho Chang 《Solid State Communications》2003,127(7):509-514
Li[NixLi(1/3−2x/3)Mn(2/3−x/3)]O2 (X=0.17, 0.25, 0.33, 0.5) compounds are prepared by a simple combustion method. The Rietvelt analysis shows that these compounds could be classified as having the α-NaFeO2 structure. The initial charge-discharge and irreversible capacity increases with the decrease of x in Li[NixLi(1/3−2x/3)Mn(2/3−x/3)]O2. Indeed, Li[Ni0.50Mn0.50]O2 compound shows relatively low initial discharge capacity of 200 mAh/g and large capacity loss during cycling, with Li[Ni0.17Li0.22Mn0.61]O2 and Li[Ni0.25Li0.17Mn0.58]O2 compounds exhibit high initial discharge capacity over 245 mAh/g and stable cycle performance in the voltage range of 4.8 -2.0 V. On the other hand, XANES analysis shows that the oxidation state of Ni ion reversibly changes between Ni2+ and about Ni3+, while the oxidation state of Mn ion sustains Mn4+ during charge-discharge process. This result does not agree with the previously reported ‘electrochemistry model’ of Li[NixLi(1/3−2x/3)Mn(2/3−x/3)]O2, in which Ni ion changes between Ni2+ and NI4+. Based on these results, we modified oxidation-state change of Mn and Ni ion during charge-discharge process. 相似文献
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Electronic structures and magnetoresistance of Co/Cu/Ni/Cu superlattices with different Orientations
Jin-rong ZhuLi-jie Qian Jing-Guo Hu Lan ZhouZhi Zeng 《Physica B: Condensed Matter》2011,406(18):3446-3449
Electronic structures and magnetoresistance (MR) of pseudo-spin-valves structure (PSV) Co3/Cu3/Ni3/Cu3(1 0 0), Co3/Cu3/Ni3/Cu3(1 1 0), and Co3/Cu3/Ni3/Cu3(1 1 1) are studied using the full potential linearized augmented plane wave (FLAPW) method with generalized-gradient approximation (GGA) for the exchange correlation interactions. It has been found that the spin-dependence scatterings at interfaces are insignificant compared with the ones of the interior layers for the three orientation superlattices. Also, we evaluate the MR ratio by means of the two-current model, and find that the MR ratio of Co3/Cu3/Ni3/Cu3(1 0 0) (73.72%) is larger than those of structures Co3/Cu3/Ni3/Cu3(1 1 0) (68.38%), and Co3/Cu3/Ni3/Cu3(1 1 1) (67.09%). 相似文献
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L.M. Paulius B.W. Lee M.B. Maple P.K. Tsai 《Physica C: Superconductivity and its Applications》1994,230(3-4)
We present a reliable method for growing single crystals of Y1−xPrxBa2Cu3O7−δ high-Tc superconductors in ZrO2 crucibles. This method results in crystals with greatly improved superconducting properties compared to crystals grown with the previously reported methods which use Al2O3 crucibles. We describe techniques for crystal growth in both Al2O3 and ZrO2 crucibles using an excess of BaCo3 and CuO as the flux. The crystals were characterized by means of DC magnetic-susceptibility measurements, electrical-resistivity measurements, and electron microprobe analysis. The effects of Al contamination on the conditions for crystal growth and on the superconducting properties of the crystals are found to be quite significant. 相似文献
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The investigation of the manganites La2/3−xPrxSr1/3MnO3, La2/3Sr1/3−xCaxMnO3 and La2/3+xCa1/3−2xAgxMnO3, which all exhibit Mn3+:Mn4+=2, shows that it is possible to reach high magnetoresistance at room temperature, up to 21% under 1.2 T. These materials are compared to La5/6Ag1/6MnO3 which corresponds to the same Mn3+:Mn4+ ratio and exhibits a magnetoresistance of 25% in this field. An interesting feature deals with the value of the insulator-metal transition temperature TIM, often higher than TC, especially for Ag-based compounds. It is suggested that the latter results either from a better oxygenation of the surface of the grains or from a migration of silver toward the surface. 相似文献