含分散第二相粒子的离子导体AgI的电学性质

测量了纯AgI和AgI含分散第二相粒子(简称DSPP)η-Al₂O₃(0.05μm)和γ-Fe₂O₃(0.6μm)的电导率随成分和温度的变化。β-AgI的电导率随加入第二相粒子含量的增加而明显增加,大约在40—50mol％时电导出现极大值。室温下含DSPP的电导率比纯AgI增加二到三个数量级。含DSPP的α-AgI电导率降低,激活能增加。电导率测量和差热分析(DTA)表明第二相的加入明显地影响AgI从α相到β相的相转变温度,AgI(η-Al₂O₃,50mol％)α相到β相的转变温度比纯AgI低17℃。室温下对AgI(γ-Fe₂O₃,50mol％)的直流极化实验表明电子电导是n型导体,电子电导率与总电导率相比可以忽略。 关键词：     

分散第二相γ-Al_2O_3对β-Li_2SO_4离子导电性的影响

本文研究了分散第二相γ-Al_2O_3对β-Li_2SO_4离子导电性的影响。β-Li_2SO_4(γ-Al_2O_3)的电导率随γ-Al_2O_3含量的增加而提高,到γ-Al_2O_3为50mol％时达到极大。当温度为253℃时,β-Li_2SO_4(50mol％γ-Al_2O_3)的电导率比纯β-Li_2SO_4增加约四个数量级。γ-Al_2O_3使α-Li_2SO_4的电导率降低。在相对湿度为70—80％条件下制备的β-Li_2SO_4(γ-Al_2O_3)的电导率随γ-Al_2O_3含量增加而单调上升。~7Li核磁共振吸收谱的叠加小峰也随γ-Al_2O_3含量的增加而趋于明显。结果表明这是由于γ-Al_2O_3表面吸附水的影响。实验还表明,淬火对β-Li_2SO_4(30mol％γ-Al_2O_3)样品的电导率有显著影响。160℃时淬火样品的电导率比未淬火样品高两个数量级。     

无锂助熔剂B_2O_3对Li_(1.3)Al_(0.3)Ti_(1.7)(PO_4)_3固体电解质离子电导率的影响

采用固相法制备锂离子电池用固体电解质磷酸钛锂铝Li_(1.3)Al_(0.3)Ti_(1.7)(PO_4)_3(LATP),研究了不同烧结温度以及助熔剂对LATP固体电解质离子电导率的影响.采用X射线衍射、能谱分析、扫描电镜和交流阻抗等方法,研究样品的结构特征、元素含量、形貌特征以及离子导电性能.结果表明,在900?C烧结可以获得结构致密、离子电导率较高的纯相LATP陶瓷固体电解质.与添加助熔剂Li BO2的样品进行对比实验发现,采用B_2O_3代替LiBO_2作为助熔剂也可以提高烧结样品的离子电导率,并且电解质的离子电导率随助熔剂添加量的增大,先增大后减小,其中添加质量百分比为2%的B_2O_3的样品具有最高的室温离子电导率,为1.61×10~(-3)S/cm.     

Bi_2O_3-Y_2O_3系高氧离子导体的离子电导和电子电导的研究

用交流电桥法研究了Bi_2O_3 Y_2O_3体系含22.5—30mol％Y_2O_3烧结试样在po_2值由1至10~(-21)atm范围内氧离子的电导率,实验证明该种材料的氧离子电导率比同温度下ZrO_2基固体电解质高若干倍;用这种材料作为固体电解质组成氧浓差电池,电池电动势和理论电动势的比值E/E_0等于1或接近1,说明这种材料几乎为纯氧离子导体,p型电子空穴导电性很小;用库伦滴定抽氧法测定了含Y_2O_3 27.5mol％样品的电子导电特征氧分压,其值为lgpe＇=(-767000/T)+655,电子导电性极小。可期望为一种新型氧离子导体材料。     

LiF-LiCl-B_2O_3系统非晶态快离子导体结构的研究

本文通过对~(11)B核磁共振(~(11)B-NMR)、红外光谱等实验方法,研究了LiF-LiCl-B_2O_3三元系统玻璃的结构和离子导电性,着重于F~-离子在玻璃网络中所起的作用,以及 F~-,Cl~-和Li~ 离子对导电率的影响。 LiF-LiCl-B_2O_3三元系统玻璃,随LiF含量的增加,B由三角体向四面体变化,从而F~-离子进入网络,使玻璃结构由[B_2O_3]三角体层状结构向三维空间延展,形成了含有[BO_3F]基团的三维空间网络,Cl~-离子以游离的离子存在于网络中,起着松散网络的作用,对提高电导率有利,而Li~ 离子作为传导离子,对电导率的贡献是主要的。本系统玻璃的电导率是随LiF,LiCl含量的增加而增大,在300℃时测得电导率σ= 6.12×10~(-4)Ω~(-1)·cm~(-1)。     

离子导体LiCl(Al_2O_3)的核磁共振研究

本文报道了含分散第二相粒子的离子导体LiCl(或LiI)中~7Li核磁共振的观测结果,测量了~7Li核磁共振吸收谱线的线宽和自旋-晶格弛豫时间(T_1)。实验发现,在LiCl(Al_2O_3)中,~7Li的核磁共振吸收谱线上叠加了一小峰,且随第二相粒子的类型、含量和温度而变化。~7Li核磁共振信号的信噪比显著提高,自旋-晶格弛豫时间变短,且也随第二相粒子的类型、含量和温度而变化。结果表明,离子电导率的提高和附加小峰的出现都是由第二相粒子引起的,从而提出:靠近第二相粒子的LiCl界面附近的空间电荷区中高的离子传导是离子电导率提高和附加小峰出现的可能机理。     

沉淀法制备Li~+、Na~+掺杂Gd_2O_3:Eu~(3+)荧光粉及发光特性研究

用沉淀法制备Li~+、Na~+和Eu~(3+)共掺Gd_2O_3荧光粉,并与微波-固相法制备的样品进行了比较。通过测量该粉体的XRD、激发光谱和发射光谱,比较了样品的微观结构和讨论了不同合成条件对Gd_2O_3:Eu~(3+)荧光粉发光特性的影响。结果显示在相同的条件下,对于未掺入Li~+的Gd_2O_3:Eu~(3+)样品比较,沉淀法制备样品的发光强度是微波-固相法制备样品的1.68倍;掺入Li~+的Gd_2O_3:Eu~(3+)样品比较,沉淀法制备样品的发光强度是微波—固相法制备样品的1.82倍。当使用草酸作为沉淀剂,掺杂浓度为Li~+(4.5 mol%)、Na~+(4.5mol%)、Eu~(3+)(4.5mol%),在800℃煅烧2h后获得样品的发光强度,是Gd_2O_3:Eu~(3+)荧光粉的5.91倍。     

Li~+、Na~+共掺(Y_xGd_yLu_(1-x-y))_2O_3∶0.5%Pr~(3+)荧光粉的制备及发光特性研究

用高温固相法制备了Li~+,Na~+共掺(Y_xGd_yLu_(1-x-y))_2O_3∶0. 5%Pr3~+荧光粉末。用XRD对样品进行结构表征,用扫描电镜观测了样品的形貌,测量了样品的激发光谱、发射光谱及发光衰减曲线。结果显示,Li~+、Na~+和Pr~(3+)的掺杂没有引起(Y_xGd_yLu_(1-x-y))_2O_3立方晶相结构的改变。在单一基质中掺杂的Li~+、Na~+可有效改善晶粒尺寸,在复合基质中掺杂的Li~+、Na~+,不仅可以有效改善晶粒尺寸,还使得样品有陶瓷化的趋势。在272 nm激发下,粉末样品在632 nm处均呈现较强的Pr~(3+)红色发射。不同条件下,1 000℃煅烧2 h获得的(Y_(0. 05)Gd_(0. 05)Lu_(0. 9))_2O_3∶0. 5%Pr~(3+),2. 5%Li~+,1%Na~+荧光粉末的发光最强,且荧光寿命较短。     

Li~+,Zn~(2+),Mg~(2+)掺杂Lu_2O_3∶Er~(3+)荧光粉的制备及发光特性

用微波高温固相法合成了Er~(3+)单掺Lu_2O_3,Li~+与Er~(3+)共掺Lu_2O_3及Li~+,Zn~(2+),Mg~(2+)掺杂Lu_2O_3∶Er~(3+)的荧光粉。实验表明金属离子Li~+、Zn~(2+)、Mg~(2+)、Er~(3+)掺杂Lu_2O_3,不影响Lu_2O_3的立方晶相。扫描电子显微镜测量表明,Li~+掺杂可以有效改善粉体的分散性和形貌,Li~+,Zn~(2+),Mg~(2+)共掺杂获得的粉体颗粒分布更加均匀,粒径范围为80～100 nm。379 nm激发下,Li~+与Er~(3+)共掺样品发光较单掺Er~(3+)样品在565 nm处的发光增强了4.5倍,而Li~+、Zn~(2+)、Mg~(2+)与Er~(3+)共掺样品较其发光增强5.3倍。980 nm激发下,Li~+与Er~(3+)共掺样品,Li~+、Zn~(2+)、Mg~(2+)与Er~(3+)共掺样品的发光分别比单掺Er~(3+)样品在565 nm处发光增强23倍与39倍,在662 nm处发光强度分别增强20倍与43倍。379 nm激发下,较单掺Er~(3+)的样品,掺杂Li~+的样品和Li~+,Zn~(2+),Mg~(2+)和Er~(3+)共掺的样品荧光寿命均有所增加,而Zn~(2+)、Er~(3+)共掺及Mg~(2+)、Er~(3+)共掺样品的荧光寿命则有所缩短。     

Li_2SO_4—Li_2B_2O_4,Li_2SO_4—(NH_4)_2SO_4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Li_2SO_4-Li_2B_2O_4和Li_2SO_4-[NH_4]_2SO_4两个赝二元系相图进行了研究。Li_2SO_4-Li_2B_2O_4是共晶体系,共晶温度为720℃,共晶点在含75mol％Li_2SO_4处。在Li_2SO_4-[NH_4]_2SO_4体系中只有一个包晶化合物LiNH_4SO_4,它在186℃附近有一个固态相变。 研究了Li_2BO_4晶态和非晶态及Li_2SO_4-(NH_4)_2SO_4体系中三种不同成分样品的离子导电性,发现在400℃以下非晶态Li_2B_2O_4的电导率比晶态至少高两个数量级,而且电导激活能大大降低。Li_2NH_4SO_4高温相电导激活能为0.12eV,而室温相为0.70eV.含Li_2SO_440mol％的样品(即LiNH_4SO_4和[NH_4]_2SO_4二相混合物)在高温相的电导率比纯LiNH_4SO_4高约两个数量级,这表明在一种离子晶体中加入适量的另一种离子晶体,可以使前者的电导率大幅度提高。     

The orientational glass instability and localization in (KCN) x (KBr)1−x and (KCN) x (NaCN)1−x

Substitutional disorder in mixed crystals with orientational and translational degrees of freedom leads to the appearance of random strain fields. The strains act as static scattering centers for dynamic modes. Near a ferroelastic phase transition where the crystal is very soft, internal friction processes dominate the dynamic restoring forces. The resulting nonergodic instability marks the onset of the orientational glass state, which is characterized by a freezing-in of orientational and translational modes without long range order. The method is based on the study of dynamic equations of mode-coupling type and was originally developed by Götze for the Anderson localization.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday     

Dielectric properties of (KBr)1−x (KCN) x

The temperature dependence of the dielectric constant of (KBr)_1–x (KCN) _x was measured at frequencies of 87.5 Hz, 1, 10 and 100 kHz for concentrations ofx=0, 0.01, 0.04, 0.14, 0.25, and 0.50. Both the real and the imaginary part showed maxima at characteristic temperatures which depend on the measuring frequency and the concentration. The results are analogous to the behaviour of the magnetic susceptibility in spin glasses and support the existence of an orientational glass state.     

Non-ergodic instability and the quadrupolar glass state in K(CN) x Br1−x and (NaCN) x (KCN)1−x

Random strain fields, due to substitutional disorder, couple to translational and orientational dynamic modes in plastic crystals. One distinguishes the cases of weak and strong random fields. In weak fields, the crystal comes close to a structural phase transition. Then elastic restoring forces are weak while internal friction dominates. The resulting non ergodic instability marks the onset of a structural glass state. The evolution of the glass state is discussed within a selfconsistent theory. The results of an extensive numerical study are compared with experiment. In presence of strong random fields no instability occurs, and orientational freezing is a continuous process.     

Optical Properties of the (CuInSe2) x ·(2ZnSe)1−x and (CuInTe2) x (·2ZnTe)1−x Solid Solutions

Crystals of the compounds CuInSe₂, CuInTe₂, ZnSe, and ZnTe, and the solid solutions (CuInSe₂) _x ·(2ZnSe)_1–x and (CuInTe₂) _x ·(2ZnTe)_1–x were grown by the Bridgman and chemical transport reactions methods. Their transmission and reflection spectra in the region of the main absorption line edge were studied. The forbidden band gap of the indicated materials was determined and its concentration dependences were built for the solid solutions. It is established that the forbidden band gap changes linearly with the x composition and is satisfactorily described by the square-law dependence.     

Ge self-diffusion in epitaxial Si(1)-(x)Ge(x) layers

Diffusion coefficients and activation energies have been determined for Ge diffusion in strain-relaxed Si(1)-(x)Ge(x) with x = 0.00, 0.10, 0.20, 0.30, 0.40, and 0.50. The activation energy drops from 4.7 eV in Si and Si(0.90)Ge(0.10) to 3.2 eV at x = 0.50. This value compares with the literature value for Ge self-diffusion in Ge, suggesting Ge-like diffusion already at x approximately equal to 0.5. The effect of strain on the diffusion was also studied showing a decrease in diffusion coefficient and an increase in activation energy upon going from compressive over relaxed to tensile strain.     

Phases and phase transitions of (NaCl)1−x(NaCN)x

(NaCl)_1–x(NaCN)_x mixed crystals with CN-concentrationsx of 0.87, 0.76, 0.71 and 0.65 have been investigated by X-ray powder diffraction. Apart from the cubic room temperature phase, a rhombohedral and an orthorhombic phase have been identified. In addition a glass state has been observed which is characterized by a strong broadening of the cubic powder lines. The phase diagram shows a wide coexistence gap between the non-cubic phases and the glass state.