共查询到17条相似文献,搜索用时 218 毫秒
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木文研究了Al2O3对B2O3-0.7Li2O-0.7LiCl非晶态的形成和电学性能的影响,我们发现:加入适量的Al2O3后,无需借助液氮骤冷技术,直接将熔体倾倒在室温下的紫铜板上就很容易形成大块非晶锂离子导体B2O3-0.7Li2O-0.7LiCl-xAl2O3。Al2O3的加入使B2O3-0.7Li2O-0.7LiCl的电导率有所降低,但在高温下不太明显,电导激活能略微升高,实验发现:Al2O3含量x=0.03是较合适的剂量,较容易形成大块非晶态,对电导率的影响也不大。
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本文研究了非晶锂离子导体P2O5-0.7Li2O-0.4LiCl-0.1Al2O3的60目、120目、200目粉末、粉末压片和整片非晶在60至380℃的离子电导率和激活能。发现颗粒度减小能使离子电导率提高四倍以上,但不影响激活能,它归因于同一非晶相的界面效应。各样品在380℃等温热处理76h内的离子电导率和X射线衍射研究表明:颗粒度越小,晶化就越容易。整片非晶比粉末压片不仅电导率提高两个数量级,激
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本文报道了非晶态离子导体Li2B2O4的7Li核磁共振研究。测量了7Li核磁共振谱与温度的关系。实验中发现,Li2B2O4的晶态、非晶态和部分晶化样品的7Li核磁共振谱有很大的不同,且在部分晶化样品的7Li核磁共振谱上有附加的小峰,它与LiCl(Al2O3)的7Li核磁共振谱上附加的小峰相类似。我们也对非晶态离子导体B2O3-0.7Li2O-0.7LiCl进行了7Li核磁共振研究,其结果与上面的类似。研究结果表明,它们都起因于非晶母体与微晶的界面效应。
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本文用中国第一台正电子湮没辐射一维角关联实验装置,测量了非晶锂离子导体B2O-0.7Li2O-0.7LiCl-xAl2O3(x=0.15;0.10;0.05)晶化过程中各条正电子湮没辐射的一维角关联曲线,并对归一化的电子动量分布进行了线形参数的计算,从其S参数同样能推测出该离子导体在晶化过程中缺陷浓度的变化。非晶离子导体B2O3-0.7Li2O-0.7LiCl-xAl2O3的实验结果表明,Al2O3组分不同,对非晶态样品在室温下一维角关联曲线的S参数亦无较大影响。完全晶化后,一维角关联曲线的S参数均有很大下降。在晶化过程最初期,无论Al2O3含量多少,S参数都明显略增;到晶化温度附近,仅对Al2O3含量较多的非晶,S参数反常增高。这些结果验证和补充了测正电子平均寿命得出的结论。由此初步证实了界面层有大量缺陷的物理图象。
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通过真空密封热处理、避免了样品晶化后吸水引起的误差,采用脉冲法在293K和77K测量了晶化过程初期三种非晶锂离子导体B2O3-0.7Li2O-0.7LiCl-xAl2O3(x=0.15,0.10和0.05)的7Li核磁共振谱。发现在低温(77K)只有固相锂离子对应的自旋-自旋弛豫时间T2=87μs,严格按高斯函数衰减。在室温下固相锂离子对应的T2s=127μs,仍是高斯型;但液相锂离子对应的T2却按洛仑兹函数衰减。这反映出锂离子导体的固-液二相性。三种非晶B2O3-0.7Li2O-0.7LiCl-xAl2O3(x=0.15,0.10和0.05)分别在热处理温度401,388和381℃附近,其液相锂离子对应的T2l都剧增,其吸收谱线宽都变窄。由此再次验证了非晶母体与微晶之间的两相界面效应的物理图象。
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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。
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Molecular dynamics simulation of binary glass 52Li2O-48P2O5 and ternary glasses 45Li2O-42P2O5-13LiCl and 39Li2O-36P2O5-25LiCl was undertaken to study the effects of the addition of LiCl to the binary phosphate glass. The results show that addition of LiCl in the glass creates more non-bridging oxygens and reduces P-O-P chain lengths and branches in these chains, leading to a weakening of the glass matrix and consequent lowering of Tg. Interchain linkages mediated by Li in the binary structure diminish, and consequently better channels are created for Li+ movement, enhancing the ionic conductivity σ. Structure parameters also indicate the absence of LiCl clusters in the glass matrix. 相似文献
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A comparative investigation on Li+ ion transport has been carried out in various phases of lithium metaphosphate such as (i) crystalline LiPO3, (ii) glassy form as mol % 50Li2O-50P2O5, synthesized by melt-quenching process, (iii) single phase glass-ceramic LiPO3 obtained through controlled heat treatment of mol % 50Li2O-50P2O5 and (iv) newly identified polymer-metal salt complex (PEO)6: LiPO3. All of the above materials have been characterized through XRD, DSC, optical microscopy and impedance spectroscopy techniques.
The Li+ ions, migrating with an activation energy value of 1.4 eV through “interstitial mechanism” in polycrystalline LiPO3, exhibited a dc conductivity value of 2.5×10-8 Scm-1 at 280 °C. The above conductivity value was enhanced by four orders of magnitude in Li2O-P2O5 glass, with an activation energy value of 0.72 eV. The glass subjected to controlled heat treatment devitrified into single
phase glass-ceramic, as revealed by XRD and optical microscopy studies. The glass-ceramic exhibited better conduction characteristics
compared to polycrystalline LiPO3. Polycrystalline LiPO3, complexed with polymer PEO has exhibited a conductivity value of 3.1×10-7 Scm-1 at 78 °C with activation energies of 0.21 and 0.88 eV for Li+ ion migration above and below the softening point of the polymer, respectively.
PACS 66.10.Ed; 71.55.Jv; 81.30.Hd; 82.45.Gj; 82.45.Wx 相似文献
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A. Arvind V.K. Shrikhande G.P. Kothiyal 《Journal of Physics and Chemistry of Solids》2008,69(11):2622-2627
We have prepared lithium aluminum silicate (LAS) glasses of compositions (wt%) 10.6Li2O-71.7SiO2-7.1Al2O3-4.9K2O-3.2B2O3-2.5P2O5(LAS-P) and 10.6Li2O-71.7SiO2-7.1Al2O3-4.9K2O-3.2B2O3-1.25P2O5-1.25TiO2 (LAS-PT) by the conventional melt quench technique. P2O5 and TiO2 are added as nucleating agents to transform them into glass ceramics. We have studied the interdependence of different phases formed, microstructure, thermal expansion coefficient (TEC), and microhardness (MH) using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-mechanical analysis (TMA), and MH (μ-hardness) measurements. The incorporation of TiO2, in addition to P2O5, greatly affects phase evolution and morphology, thereby affecting the thermo-physical properties. Its presence resulted in the formation of only lithium disilicate phase in LAS-PT samples as compared to lithium disilicate and quartz in LAS-P samples on heat treatment at 820 °C. This produced low-aspect-ratio plate-like crystallites in LAS-PT vis-à-vis granular microstructure in LAS-P. Consequently due to the combined effect of both phase formation and morphology a single-phase glass ceramic with overall higher MH, TEC, and glass transition temperature (Tg) is produced. 相似文献
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To investigate the influence of cation mobility variation due to the mixed glass former effect, 0.45Li2O-(0.55 − x) P2O5−x B2O3 glasses (0 ≤; x ≤ 0.55) are studied keeping the molar ratio of Li2O/(P2O5 + B2O3) constant. Addition of B2O3 into lithium phosphate glasses increases the glass transition temperature (T
g) and number density, decreases the molar volume, and generally renders the glasses more fragile. The glass system has been
characterised experimentally by XRD, XPS and impedance studies and studied computationally by constant volume molecular dynamics
(MD) simulations and bond valence (BV) method to identify the structural variation with increasing the B2O3 content, its consequence for Li+ ion mobility, as well as the distribution of bridging and non-bridging oxygen atoms. These studies indicate the increase
of P-O-B bonds (up to Y = [B2O3]/([B2O3] + [P2O5]) ≈ 0.5 and B-O-B bonds, as well as the decrease of P-O-P bonds and non-bridging oxygens (NBOs) with rising B2O3 content. The system with Y ≈ 0.5 exhibits maximum ionic conductivity, 1.0 × 10−7 S cm−1, with activation energy 0.63 V. Findings are rationalised by a model of structure evolution with varying B2O3 content Y and an empirical model quantifying the effect of the various structural building blocks on the ionic conductivity in this
mixed glass former system. 相似文献
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The glass-ceramic samples with the general formula: (100???x) [0.4Li2O-0.1GeO2-0.6P2O5]?+?x 40-h ball-milled Al2O3 (where x?=?0, 2, 4, 6, 8, 10, and 12 mol%) were synthesized by high-energy ball milling technique. X-ray diffraction (XRD) analysis revealed that the phases such as LiGe2(PO4)3, Li4P2O7, GeO2, and AlPO4 were identified from major diffraction peaks of LGPA samples. The intensity and broadening of XRD peaks of LGPA glass-ceramic samples displayed that the LGPA10 glass-ceramic possesses major crystalline phases namely sodium super ionic conductor (NASICON)-type phases of LiGe2(PO4)3 and Li4P2O7. Scanning electron micrograph (SEM) pictures further confirmed that the sample LGPA10 has the presence of particles of varied sizes (20–30 nm) and also large clusters of less than 60 nm dispersed uniformly in a continuous glass matrix. The slight difference in the Z″ and M″ peaks for the LGPA samples suggests the presence of possibly more than one mechanism. 相似文献