Li4SiO4-Li3VO4赝二元系和Li4GeO4-Li4SiO4-Li3VO4赝三元系中新的锂离子导体

本文在室温到300℃的温度范围内研究了Li₄SiO₄-Li₃VO₄和Li₄GeO₄-Li₄SiO₄-Li₃VO₄体系中的离子导电性,发现γ_II相固溶体Li_3+xV_1-xSi_xO₄是好的锂离子导体。所研究的成分中Li_3.3V_0.7Si_0.3O₄的离子电导率最高,室温下为1×10^-5Ω^-1·cm^-1,在42—192℃的电导激活能为0.36eV,电子电导率可以忽略,因而这是迄今所发现的最好的锂离子导体之一。粗略确定了Li₄GeO₄-Li₄SiO₄-Li₃VO₄三元系中电导率高的范围,发现在Li_3.5V_0.5Ge_0.5O₄中Si部分取代Ge可以使电导率进一步提高,Li_3.5V_0.5Ge_0.4Si_0.1O₄的室温电导率可达1.3×10^-5Ω^-1·cm^-1,电导激活能为0.40eV。 关键词：     

Li3VO4-Li4TO4(T=Ge,Si)固溶体离子导体7Li的NMR研究

在150—573K温度范围内,研究了固溶体Li₃VO₄-Li₄TO₄(T=Ge,Si)系统不同成分的⁷Li的NMR谱。发现γ_II相固溶体室温⁷Li的NMR线宽和自旋晶格弛豫时间T₁的值都比Li₄GeO₄,Li₄SiO₄和Li₃VO₄小约一个数量级。这表明在γ_II相固溶体离子导体中,Li⁺离子运动有可能比固溶前有数量级增长。同时还发现⁷Li的电四极分裂伴线数随成分和温度而异,以及伴线强度百分比依赖于温度。这反映γ_II相的不同成分中,间隙Li⁺离子占有的不等价位置个数不同,而Li⁺离子在每个不等价位置上的占有率又随温度而变化。 关键词：     

Li2SO4—Li2B2O4,Li2SO4—(NH4)2SO4赝二元系相图及离子导电性研究

本文用差热分析和X射线衍射方法对Li₂SO₄-Li₂B₂O₄和Li₂SO₄-[NH₄]₂SO₄两个赝二元系相图进行了研究。Li₂SO₄-Li₂B₂O₄是共晶体系,共晶温度为720℃ 关键词：     

BaO-Li2O-B2O3三元系中BaB2O4-Li2B2O4和BaB2O4-Li2O截面相平衡关系的研究

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：     

Li_3VO_4-Li_4SiO_4-Li_4GeO_4赝三元系相图的研究

本文用差热分析法和高温、室温X射线衍射法对Li_3VO_4,Li_4SiO_4的相变过程,Li_3VO_4-Li_4SiO_4,Li_3O_4-Li-4GeO_4赝二元系相图以及Li_3VO_4-Li_4SiO_4-Li_4GeO_4赝三元系相图室温截面进行了研究。发现在Li_3VO_4-Li_4SiO_4,Li_3VO_4-Li_4GeO_4赝二元系中,由于Li_4SiO_4或Li_4GeO_4的加入而使Li_3VO_4的高温γ_(II)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。     

插层化合物LiV2O4的制备与实验研究

用化学方法从层状化合物LiVO₂中引出0.5个Li后得到Li_0.5VO₂,再经过低温真空热处理制备出尖晶石结构化合物LiV₂O₄,类似地处理Li_0.465VO₂,得到缺Li的Li_0.93V₂O₄,LiV₂O₄和Li_0.93V 关键词：     

LiNaSO4-MgSO4赝二元系中离子导体的研究

本文用差热分析和X射线衍射方法,对LiNaSO₄-MgSO₄赝二元系相图进行了研究。在此体系中存在三个化合物,它们分别为(LiNa)_0.8Mg(0.2)SO₄,(LiNa)_0.67Mg_0.33SO₄和(LiNa)_0.4Mg_0.6SO₄。研究了三种化合物的离子导电性,在490℃时上述三个化合 关键词：     

Al-Ti-V-M四元系合金TiAl3-VAl3-MAl3(M=Ni,Fe)赝三元系相图的室温截面

本文用X射线衍射法测定了Al-Ti-V-M四元系合金TiAl₃-VAl₃-MAI₃(M=Ni,Fe)两个赝三元系相图的室温截面。(1)TiAl₃-VAl₃NiAl₃赝三元系相图室温截面由一个单相点ε(NiAl₃)、一个单相区δ(TiAl₃和VAl₃形成的连续固溶体)和一个两相区δ+s所组成。(2)TiAl关键词：     

Ca2GeO4 ∶Eu3+ 的电子结构和紫外-真空紫外发光特性的研究

采用高温固相法合成了发光材料Ca₂GeO₄ ∶Eu³⁺ ,并详细研究了其紫外-真空紫外发光特性. 发现并解释了Eu³⁺ 离子在空气中的自还原以及在不同波长激发下的颜色转换现象. Ca₂GeO₄ ∶Eu³⁺ 在163—230和301,466 nm处具有强激发带,表明Ca₂GeO₄ ∶Eu³⁺ 关键词： 2GeO₄ ∶Eu³⁺')" href="#">Ca₂GeO₄ ∶Eu³⁺ 光致发光机理 空气中自还原 颜色转换     

Li2K(IO3)3与Li2NH4(IO3)3的晶体结构

本文用X射线粉末法测定了Li₂K(IO₃)₃与Li₂NH₄(IO₃)₃的晶体结构和原子参数。发现Li₃K(IO₃)₃,Li₂NH₄(IO₃)₃与Li₂Rb(IO₃)₃同晶型,属单斜晶系,空间群为P2₁/α,每个单胞含有四个化合式量。室温的点阵常数分别为α=11.198?,b=11.046?,c=8.254?,β=111.53°,及α=11.327?,b=11.078?,c=8.341?,β=111.87°。讨论了二元化合物的形成与离子半径的关系。 关键词：     

Li+ ion conducting γ solid solutions in the systems Li4XO4-Li3YO4: X=Si,Ge, Ti; Y=P,As, V; Li4XO4-LiZO2: Z=Al,Ga, Cr and Li4GeO4-Li2CaGeO4

A wide variety of solid solutions with a structure related to that of γ Li₃PO₄ may be prepared. These include materials such as lisicon, Li_2+2xZn_1-xGeO₄ and the title systems, many of which have not been studied previously. Conductivity data are presented for eight systems: Li₄GeO₄-Li₃(P, As, V)O₄; Li₄TiO₄-Li₃(As, V)O₄; Li₄GeO₄-Li(Ga, Al)O₂; Li₄GeO₄-Li₂CaGeO₄ and the results compared with those reported in the literature for Li₄SiO₄-Li₃(P, As, V)O₄ systems and lisicon. dc polarisation measurements were made on four of the system and it was found that the electronic transference number is 10^?4 or less. The materials with the highest conductivity were found in the systems, Li₄ (Ge, Ti) O₄-Li₃ (As, V)O₄ with σ ~ (3 to 4) × 10^?5 Ω^?1 cm^?1 at room temperature. It is noted that the systems with the highest conductivity are generally those with the largest unit cell volume.     

New Li+ ion conductors in the system Li4SiO4−Li3AsO4

In the system Li₄SiO₄-Li₃AsO₄, Li₄SiO₄ forms a short range of solid solutions containing up to 14 to 20% Li₃AsO ₄, depending on temperature, and γ-Li₃AsO₄ forms a more extensive range of solid solutions containing up to ≈55% Li₄SiO₄. The Li₄SiO₄-Li₃AsO₄ phase diagram has been determined and is of binary eutectic character. The ac conductivity of polycrystalline samples was measured over the range 0 to at least 300°C for nine different compositions. The two solid solution series have much higher conductivity than the pure end-members; maximum conductivity was observed in the γ-Li₃AsO₄ solid solutions containing ≈40 to 55% Li₄SiO₄, with values of $\text{≈2×10}{}^{\mathrm{?6}}\text{Ω}{}^{\mathrm{?1}}\text{cm}{}^{\mathrm{?1}}$ at 20°C rising to ≈0.02 Ω^?1 cm^?1 at 300°C. These values are comparable to those found in the system Li₄SiO₄-Li₃PO₄. The variation with composition of the Arrhenius prefactor and activation energy has been interpreted in terms of the mechanisms of conduction. Li₃AsO₄ is a poor conductor essentially because the number of mobile Li⁺ ions is very small. This number, and hence the conductivity, increases dramatically on forming solid solutions with Li₄SiO₄, by the creation of interstitial Li⁺ ions. At ≈40 to 55% Li₄SiO₄, the number of mobile Li⁺ ions appears to be optimised. An explanation for the change in activation energy of conduction at ≈290°C in Li₄SiO₄ and at higher temperatures in Li₄SiO₄ solid solutions is given in terms of order-disorder of the Li⁺ ions.     

NMR study of Li+-ion diffusion in the solid solution Li3+x(P1−x,Six)O4> with the γII-Li3PO4 structure

Diffusive motion of a Li⁺ ion in the solid solution of Li₃+x(P₁?x, Si_x)O₄ (0?x?0.4) with the γ_II-Li₃PO₄ structure was studied by the measurement of the ⁷Li spin-lattice relaxation time. The observed motion was a local motion instead of a long-range one. In comparison with the previous study on the solid solution of Li₄?x(P_x, Si₁?x)O₄ with the Li₄SiO₄ structure, it is noticeable that the activation energy is low and almost independent of the composition and that the attempt frequency is smaller in this phase. These characteristics were attributed to the availability of a large interstitial void in the γ_II-Li₃PO₄ structure. The low values of activation energy for the Li⁺ ionic conduction may be explained on the same basis.     

Li4GeO4-Zn2GeO4赝二元系相图的研究

本文用差热分析和X射线衍射的方法对Li₄GeO₄-Zn₂GeO₄赝二元系相图进行了研究。结果指出,文献中所报道的锂离子导体Li₁₄Zn(GeO₄)₄不是化合物,而是含Zn₂GeO₄的以Li₄GeO₄为基的固溶体,由于Zn₂GeO₄的加入,使Li₄GeO₄的高温相稳定存在于室温。根据研究结果,提出了关于Li₁₄Zn(GeO₄)₄多晶陶瓮样品在室温长期放置后,电导率明显降低的解释。     

Etude par R.P.E. d'electrolytes vitreux appartenant au systeme B2O3-Li2O-LiCl

An EPR study of fast Li⁺ ion vitreous conductors belonging to the B₂O₃-Li₂O-LiCl system has been carried out. The samples have been subjected to X-ray irradiation at room temperature. Two types of paramagnetic centers have been observed. The first one is the Cl₂^- species (Vk center) present in the part of the vitreous domain which corresponds to low LiCl concentrations, it vanishes when Li⁺ and Cl^- begin to order. The second one is of the B.O.H.C. type often present in alkali borate glasses. Its presence shows the similarity between the boron-oxygen network of the alkali borate glasses and of our samples containing alkali chloride.     

Combustion synthesis and luminescent properties of a new material Li2(Ba0.99,Eu0.01)SiO4:B for ultraviolet light emitting diodes

Using urea as fuel and boric as flux, a novel bluish green emitting phosphor Li₂(Ba_0.99,Eu_0.01)SiO₄:B³⁺ has been successfully synthesized using a combustion method. The material has potential application as the fluorescent material for ultraviolet light-emitting diodes (UV-LEDs). The dependence of the properties of Li₂(Ba_0.99,Eu_0.01)SiO₄:B³⁺ phosphors upon urea concentration, boric acid doping and initiating combustion temperature were investigated. The crystallization and particle sizes of Li₂(Ba_0.99,Eu_0.01)SiO₄:B³⁺ have been investigated by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Luminescence measurements showed that the phosphors can be efficiently excited by ultraviolet (UV) to visible region, emitting a bluish green light with peak wavelength of 490 nm. The results showed that the boric acid was effective in improving the luminescence intensity of Li₂(Ba_0.99,Eu_0.01)SiO₄ and the optimum molar ratio of boric acid to barium nitrate was about 0.06. The optimized phosphors Li₂(Ba_0.99,Eu_0.01)SiO₄:B_0.06³⁺ showed 160% improved emission intensity compared with that of the Li₂(Ba_0.99,Eu_0.01)SiO₄ phosphors under UV (λ_ex=350 nm) excitation.     

Ca2SiO4:Dy3+材料的制备及其发光特性

采用高温固相法制备了Ca₂SiO₄:Dy³⁺发光材料.在365nm紫外光激发下,测得Ca₂SiO₄:Dy³⁺材料的发射光谱为一多峰宽谱,主峰分别位于486nm,575nm和665nm处;监测575nm发射峰,测得材料的激发光谱为一多峰宽谱,主峰分别位于331nm,361nm,371nm,397nm,435nm,461nm和478nm处.研究了Dy³⁺掺杂浓度对Ca₂SiO₄:Dy³⁺材料发射光谱及发光强度的影响,结果显示,随Dy³⁺浓度的增大,黄、蓝发射峰强度比(Y/B)逐渐增大,利用Judd-Ofelt理论解释了其原因;随Dy³⁺浓度的增大,Ca₂SiO₄:Dy³⁺材料发光强度先增大,在Dy³⁺浓度为4 mol%时到达峰值,而后减小,根据Dexter理论其浓度猝灭机理为电偶极-电偶极相互作用.研究了电荷补偿剂Li⁺,Na⁺和K⁺对Ca₂SiO₄:Dy³⁺材料发射光谱的影响,结果显示,不同电荷补偿剂下,随电荷补偿剂掺杂浓度的增大,Ca₂SiO₄:Dy³⁺材料发射光谱强度的演化趋势相同,即Ca₂SiO₄:Dy³⁺材料发射峰强度先增大后减小,但不同电荷补偿剂下,材料发射峰强度最大处对应的补偿剂浓度不同,对应Li⁺,Na⁺和K⁺时,浓度分别为4mol%,4mol%和3mol%. 关键词： 白光LED 2SiO₄:Dy³⁺')" href="#">Ca₂SiO₄:Dy³⁺ 发光特性 电荷补偿