Experimental visualization of lithium conduction pathways in garnet-type Li(7)La(3)Zr(2)O(12)

The evolution of the Li-ion displacements in the 3D interstitial pathways of the cubic garnet-type Li(7)La(3)Zr(2)O(12), cubic Li(7)La(3)Zr(2)O(12), was investigated with high-temperature neutron diffraction (HTND) from RT to 600 °C; the maximum-entropy method (MEM) was applied to estimate the Li nuclear-density distribution. Temperature-driven Li displacements were observed; the displacements indicate that the conduction pathways in the garnet framework are restricted to diffusion through the tetrahedral sites of the interstitial space.     

Synthesis and Study of Conductivity of Al-Substituted Li7La3Zr2O12

Russian Journal of Electrochemistry - The method of solid-phase sintering was used to synthesize samples of lithium-conducting Li6.4Al0.2La3Zr2O12 solid electrolyte with a garnet structure. Higher...     

Structure and dynamics of the fast lithium ion conductor "Li7La3Zr2O12"

The solid lithium-ion electrolyte "Li(7)La(3)Zr(2)O(12)" (LLZO) with a garnet-type structure has been prepared in the cubic and tetragonal modification following conventional ceramic syntheses routes. Without aluminium doping tetragonal LLZO was obtained, which shows a two orders of magnitude lower room temperature conductivity than the cubic modification. Small concentrations of Al in the order of 1 wt% were sufficient to stabilize the cubic phase, which is known as a fast lithium-ion conductor. The structure and ion dynamics of Al-doped cubic LLZO were studied by impedance spectroscopy, dc conductivity measurements, (6)Li and (7)Li NMR, XRD, neutron powder diffraction, and TEM precession electron diffraction. From the results we conclude that aluminium is incorporated in the garnet lattice on the tetrahedral 24d Li site, thus stabilizing the cubic LLZO modification. Simulations based on diffraction data show that even at the low temperature of 4 K the Li ions are blurred over various crystallographic sites. This strong Li ion disorder in cubic Al-stabilized LLZO contributes to the high conductivity observed. The Li jump rates and the activation energy probed by NMR are in very good agreement with the transport parameters obtained from electrical conductivity measurements. The activation energy E(a) characterizing long-range ion transport in the Al-stabilized cubic LLZO amounts to 0.34 eV. Total electric conductivities determined by ac impedance and a four point dc technique also agree very well and range from 1 × 10(-4) Scm(-1) to 4 × 10(-4) Scm(-1) depending on the Al content of the samples. The room temperature conductivity of Al-free tetragonal LLZO is about two orders of magnitude lower (2 × 10(-6) Scm(-1), E(a) = 0.49 eV activation energy). The electronic partial conductivity of cubic LLZO was measured using the Hebb-Wagner polarization technique. The electronic transference number t(e-) is of the order of 10(-7). Thus, cubic LLZO is an almost exclusive lithium ion conductor at ambient temperature.     

Improved Ga-doped Li7La3Zr2O12 garnet-type solid electrolytes for solid-state Li-ion batteries

Journal of Solid State Electrochemistry - Li7La3Zr2O12 (LLZO) is one of the most competent candidates as a solid electrolyte for next-generation Li-ion batteries. Although the stabilization of the...     

High Li-ion conductivity of Al-free Li7-3xGaxLa3Zr2O12 solid electrolyte prepared by liquid-phase sintering

Journal of Solid State Electrochemistry - Ga-doped Li7La3Zr2O12 (Ga-LLZO) is a promising solid electrolyte because it shows higher Li-ion conductivity than LLZO doped with other cations. In this...     

First total H+/Li+ ion exchange in garnet-type Li5La3Nb2O12 using organic acids and studies on the effect of Li stuffing

Garnet-type Li(5+x)Ba(x)La(3-x)Nb(2)O(12) (x = 0, 0.5, 1) was prepared using a ceramic method, and H(+)/Li(+) ion exchange was performed at room temperature using organic acids, such as CH(3)COOH and C(6)H(5)COOH, as proton sources. Thermogravimetric analysis showed that H(+)/Li(+) ion exchange was nearly (100%) completed using the x = 0 member with CH(3)COOH, while it proceeded to about 40% for x = 0.5 and 13% for x = 1. In C(6)H(5)COOH, proton exchange proceeded to about 82% for x = 0, ～40% for x = 0.5, and ～25% for x = 1. Similar proton-exchange trends were reported in H(2)O, where ion exchange occurs more readily for garnets with lower Li content in Li(5+x)Ba(x)La(3-x)Nb(2)O(12), that is, when excess Li ions preferentially reside in the tetrahedral sites of the garnet structure.     

Assessing the Importance of Cation Size in the Tetragonal-Cubic Phase Transition in Lithium-Garnet Electrolytes**

Lithium garnets are promising solid-state electrolytes for next-generation lithium-ion batteries. These materials have high ionic conductivity, a wide electrochemical window and stability with Li metal. However, lithium garnets have a maximum limit of seven lithium atoms per formula unit (e.g., La₃Zr₂Li₇O₁₂), before the system transitions from a cubic to a tetragonal phase with poor ionic mobility. This arises from full occupation of the Li sites. Hence, the most conductive lithium garnets have Li between 6–6.55 Li per formula unit, which maintains the cubic symmetry and the disordered Li sub-lattice. The tetragonal phase, however, forms the highly conducting cubic phase at higher temperatures, thought to arise from increased cell volume and entropic stabilisation permitting Li disorder. However, little work has been undertaken in understanding the controlling factors of this phase transition, which could enable enhanced dopant strategies to maintain room temperature cubic garnet at higher Li contents. Here, a series of nine tetragonal garnets were synthesised and analysed by variable temperature XRD to understand the dependence of site substitution on the phase transition temperature. Interestingly the octahedral site cation radius was identified as the key parameter for the transition temperature with larger or smaller dopants altering the transition temperature noticeably. A site substitution was, however, found to make little difference irrespective of significant changes to cell volume.     

The structure of lithium garnets: cation disorder and clustering in a new family of fast Li+ conductors

The structure of the fast lithium-ion conducting garnets Li5La3M2O12 (M = Ta, Nb) reveals Li+ on both tetrahedral and octahedral sites and suggests that the latter are responsible for the observed Li+ mobility via a clustering mechanism.     

过氧化合物法PLZT纳米粉体的制备和表征

掺镧的锆钛酸铅固溶体（Pb1-x,Lax）(Zry,Ti-y)1-x/4O3（简称PLZT）是一种有重要用途、性能优良的电光陶瓷材料[1]。为避免局部组成变化引起散射和保证良好的电光性能,材料的组成和均匀性非常重要。用传统的固相法制备PLZT粉体耗能大,生成的粉体颗粒大,组成均匀性差,不能满足现代高科技应用的要求。近年来研究的溶胶．凝胶[2]、柠檬酸法[3]、EDTA凝胶法[4]等湿化学法有许多优点,受到人们的关注,但这些方法需用较贵原料。而在众多的湿化学法中,以共沉淀法最为经济,并且它比传统的固相法好,能够制得均匀性好的纳米粉体。但该…     

Fabrication,Structure and Optical Properties of Zr~(4+) Doped Ba(Mg,Ta) O_3 Transparent Ceramics with High Refractive Index

Novel transparent ceramics of Zr4+ doped Ba(Mg,Ta)O3(BMT)with a high refractive index of 2.037 at 587.56 nm were successfully fabricated via high temperature solid-state-reaction sintering method.To make it transparent,the pure cubic Ba(Zr,Mg,Ta)O3 phases(BZMT)were realized in advance by skillfully modulating the lattice structure of BMT from trigonal symmetric to cubic symmetric through doping Zr4+ into the lattice of BMT crystal.Highly optical transmittance of 74% at 650 n,,which hit the upper limit of the theory,was achieved for BZMT.Both abbe number of 23.4 and the bandgap Eg of 3.22 eV have been calculated.     

Lithium dimer formation in the Li-conducting garnets Li(5+x)Ba(x)La(3-x)Ta2O12 (0 < x < or =1.6)

The garnet system Li(5+x)Ba(x)La(3-x)Ta2O12 shows an unprecedented Li+ content (x < or = 1.6) and short Li-Li distances of ca 2.44 A between majority occupied sites suggesting that the high Li+ mobility requires a complex cooperative mechanism.     

First-principles density functional calculation of electrochemical stability of fast Li ion conducting garnet-type oxides

The research and development of rechargeable all-ceramic lithium batteries are vital to realize their considerable advantages over existing commercial lithium ion batteries in terms of size, energy density, and safety. A key part of such effort is the development of solid-state electrolyte materials with high Li(+) conductivity and good electrochemical stability; lithium-containing oxides with a garnet-type structure are known to satisfy the requirements to achieve both features. Using first-principles density functional theory (DFT), we investigated the electrochemical stability of garnet-type Li(x)La(3)M(2)O(12) (M = Ti, Zr, Nb, Ta, Sb, Bi; x = 5 or 7) materials against Li metal. We found that the electrochemical stability of such materials depends on their composition and structure. The electrochemical stability against Li metal was improved when a cation M was chosen with a low effective nuclear charge, that is, with a high screening constant for an unoccupied orbital. In fact, both our computational and experimental results show that Li(7)La(3)Zr(2)O(12) and Li(5)La(3)Ta(2)O(12) are inert to Li metal. In addition, the linkage of MO(6) octahedra in the crystal structure affects the electrochemical stability. For example, perovskite-type La(1/3)TaO(3) was found, both experimentally and computationally, to react with Li metal owing to the corner-sharing MO(6) octahedral network of La(1/3)TaO(3), even though it has the same constituent elements as garnet-type Li(5)La(3)Ta(2)O(12) (which is inert to Li metal and features isolated TaO(6) octahedra).     

纳米Al2O3颗粒对纯Fe液诱导凝固过程的分子动力学模拟

采用分子动力学(MD)方法模拟了不同半径大小的纳米Al2O3颗粒夹杂在三个温度下(1750、1730和1710K)对纯Fe液的诱导凝固过程,并分析了作为诱导核心的纳米Al2O3颗粒的结构演变及其对Fe原子体系的凝固过程的影响.发现在诱导过程中,纳米Al2O3颗粒的内部保持较好的晶型结构,仅表面原子有结构变形;诱导凝固的Fe原子主要为面心立方(fcc)和密排六方(hcp)原子;纳米Al2O3颗粒的尺寸越大,发生诱导凝固的温度越高;诱导凝固得到的Fe晶体的晶格取向受纳米Al2O3颗粒在Fe液中的漂移程度影响.     

Antiferromagnetic ground state of quantum spins in the synthetic imanite, Ca3Ti2Si3O12: the lost child of the garnet family

Large single crystals of the garnet imanite, Ca(3)Ti(2)Si(3)O(12), were synthesized by a floating zone technique. Near-infrared to visible spectroscopy presents an optical gap of 1.65 eV at 4 K, proving the insulating character of this garnet compound. Electron paramagnetic resonance data indicate that the d(1) electron of Ti(3+) exhibits an orbital contribution to the spin moment (g = 1.859(1)). An antiferromagnetic state is observed below T(N) = 7 K, confirmed by magnetic susceptibility and specific heat data. X-ray diffraction investigations on powders and single crystals of imanite reveal that the crystal structure agrees well with expectations: the cubic symmetry Ia3d describes all obtained single crystal and powder diffraction data.     

Ce0.35Zr0.55La0.10O1.95对低贵金属Pt-Rh型三效催化剂性能的影响

采用共沉淀技术制备了Ce0.35Zr0.55La0.10O1.95固溶体, 其织构和结构性能以及氧化还原性能分别采用BET、XRD和程序升温(TP)技术进行了表征. 制备了低贵金属Pt-Rh型三效催化剂, 考察了Ce0.35Zr0.55La0.10O1.95对催化剂性能的影响. XRD和BET的结果表明, 经600 ℃焙烧5 h后, Ce0.35Zr0.55La0.10O1.95具有与Ce0.50Zr0.50O2相似的立方结构和高的比表面积；经1000 ℃焙烧5 h后, 仍能保持稳定的立方结构和47.25 m2•g−1的比表面积, 表现出优越的织构性能和高的热稳定性. H2-TPR和O2-TPO的结果表明, Ce0.35Zr0.55La0.10O1.95具有比Ce0.50Zr0.50O2更好的氧化还原性能. 和含Ce0.50Zr0.50O2的催化剂相比, 含Ce0.35Zr0.55La0.10O1.95的催化剂具有较宽的工作窗口, 优越的低温起燃性能, 较强的水气变换能力；催化剂经1000 ℃高温水热老化5 h后, 仍具有良好的催化活性, 表现出了优异的抗老化性能.     

Hybrid Polymer/Garnet Electrolyte with a Small Interfacial Resistance for Lithium-Ion Batteries

Li₇La₃Zr₂O₁₂-based Li-rich garnets react with water and carbon dioxide in air to form a Li-ion insulating Li₂CO₃ layer on the surface of the garnet particles, which results in a large interfacial resistance for Li-ion transfer. Here, we introduce LiF to garnet Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZT) to increase the stability of the garnet electrolyte against moist air; the garnet LLZT-2 wt % LiF (LLZT-2LiF) has less Li₂CO₃ on the surface and shows a small interfacial resistance with Li metal, a solid polymer electrolyte, and organic-liquid electrolytes. An all-solid-state Li/polymer/LLZT-2LiF/LiFePO₄ battery has a high Coulombic efficiency and long cycle life; a Li-S cell with the LLZT-2LiF electrolyte as a separator, which blocks the polysulfide transport towards the Li-metal, also has high Coulombic efficiency and kept 93 % of its capacity after 100 cycles.     

Single crystals of the filled Ti2N‐type η‐phase Ti3Zn3Ox (x = 1.07 and 1.23) prepared using a Bi flux

Single crystals of the filled Ti₂Ni‐type Ti₃Zn₃O_x η‐phase (cubic, space group Fdm) having {111} facets were obtained by heating Ti, Zn and ZnO with a Bi flux. The lattice parameter of a single crystal prepared at 800°C was 11.4990 (2) Å, which is close to that of Ti₃Zn₃O_∼0.5 (a = 11.502 Å), as reported by Rogl & Nowotny [Monatsh. Chem. (1977), 108 , 1167–1180]. The occupancies of the O1 (16c) and O2 (8a) sites were 1 and 0.071 (12), respectively, and the composition of the crystal was determined to be Ti₃Zn₃O_1.04. A single crystal from the sample prepared at 650°C had the same structure type, with a lattice parameter of 11.5286 (2) Å. However, O atoms were situated at a new 32e site in addition to the original 16c and 8a sites, and the Zn‐atom positions were split in accordance with the new O‐atom site. The chemical formula Ti₃Zn₃O_1.27 determined by X‐ray diffraction occupancy refinement agreed with the chemical composition obtained for the cross section of the single crystal determined with an electron probe microanalyzer.     

Al14Ba8La26.3Ru18Sr53.7O167: a variant of cubic perovskite with isolated RuO6 units

The crystal structure of the title aluminium barium lanthanum ruthenium strontium oxide has been solved and refined using neutron powder diffraction to establish the parameters of the oxygen sublattice and then single‐crystal X‐ray diffraction data for the final refinement. The structure is a cubic modification of the perovskite ABO₃ structure type. The refined composition is Ba_0.167La_0.548Sr_1.118Ru_0.377Al_0.290O_3.480, and with respect to the basic perovskite structure type it might be written as (Ba₈La_13.68Sr_34.32)(Al_13.92La_12.64Ru_18.08Sr_19.36)O_192−x, with x = 24.96. The metal atoms lie on special positions. The A‐type sites are occupied by Ba, La and Sr. The Ba atoms are located in a regular cuboctahedral environment, whereas the La and Sr atoms share the same positions with an irregular coordination of O atoms. The B‐type sites are divided between two different Wyckoff positions occupied by Ru/Al and La/Sr. Only Al and Ru occupy sites close to the ideal perovskite positions, while La and Sr move away from these positions toward the (111) planes with high Al content. The structure contains isolated RuO₆ octahedra, which form tetrahedral substructural units.     

异丁烷-丁烯烷基化反应催化剂的研究

固体强酸;异丁烷-丁烯烷基化反应催化剂的研究     

Syntheses, crystal structures, and physical properties of La5Cu6O4S7 and La5Cu6.33O4S7

Single crystal and bulk powder samples of the quaternary lanthanum copper oxysulfides La5Cu6.33O4S7 and La5Cu6O4S7 have been prepared by means of high-temperature sealed-tube reactions and spark plasma sintering, respectively. In the structure of La 5Cu6.33O4S7, Cu atoms tie together the fluorite-like (2)infinity[La5O4S(5+)] and antifluorite-like (2) infinity[Cu6S6(5-)] layers of La5Cu6O4S7. The optical band gap, E g, of 2.0 eV was deduced from both diffuse reflectance spectra on a bulk sample of La5Cu6O4S7 and for the (010) crystal face of a La 5Cu6.33O4S7 single crystal. Transport measurements at 298 K on a bulk sample of La 5Cu 6O 4S 7 indicated p-type metallic electrical conduction with sigma electrical =2.18 S cm(-1), whereas measurements on a La 5Cu6.33O4S7 single crystal led to sigma electrical =4.5 10(-3) S cm(-1) along [100] and to semiconducting behavior. In going from La 5Cu6O4S7 to La5Cu6.33O4S7, the disruption of the (2)infinity[Cu6S6(5-)] layer and the decrease in the overall Cu(2+)(3d(9)) concentration lead to a significant decrease in the electrical conductivity.