Lithium ordering and NMR linewidth in Li0.33TiS2

The low temperature ⁷Li linewidths and second moments have been analyzed for Li_0.33 TiS₂ and Li_0.97 TiS₂. Moment calculations demonstrate that the linewidth is a sensitive indicator of order on a two dimensional lattice of dipoles. The calculated dipolar second moment is not consistent with a simple √3 a_o superlattice in Li_0.33 TiS₂, but is consistent with a random arrangement of lithium ions and several more complex superlattices recently proposed by Kanamori and Kaburagi.     

Raman scattering in Ag-intercalated TiS2

Ag-intercalated TiS₂ has been investigated using electron diffraction and Raman scattering. The energies of the E_g-1 and A_1g modes in 1T-TiS₂ at 300 K were found to be 232 and 336 cm^-1, respectively. In Ag_0.3TiS₂, at an ambient temperature of 4.2 K, modes were observed at 207, 239, 277, 311, and 347 cm^-1. Three of these modes have been associated with the formation of a superlattice at low temperatures. The superlattice formation was observed by electron diffraction and is attributed to an ordering of the silver atoms at interlayer interstices.     

Concerning the semimetallic characters of TiS2 and TiSe2

Recent data on TiS₂ are discussed in terms of the dirty semiconductor model rather than the semimetallic model. The “T²” resistivity is attributed to scattering by “Fivaz-mode”, optic homopolar phonons rather than to electron-hole scattering.A slight semimetallic p-d overlap is finally obtained by TiSe₂ and leads to phenomena of the type expected for the ‘excitonic insulator’.     

Li ion conduction in Li2ZrO3, Li4ZrO4, and LiScO2

The results of ac and dc conductivity measurements on Li₂ZrO₃, Li₄ZrO₄, and LiScO₂ show that these phases are Li ion conductors. Even though the Li ion conductivity in these phases is quite low, 3.3×10^?5, 3.0×10^?4, and 4.2×10^?7 S m^?1 at 573 K, respectively, they are of special interest since they are among the small group of ternary oxides which may be thermodynamically stable against Li. Mechanisms are proposed for the decomposition of these phases at the anode due to Li loss during dc polarization. In addition the electrical conductivity of ternary oxide phases which are, or may be, thermodynamically stable against Li are summarized.     

Lithium insertion into Li4V3O8

The lithium insertion characteristics of lithium vanadate, Li₄V₃O₈, were investigated using LiV₃O₈ prepared by the precipitation technique as the starting material. The Li₄V₃O₈ phase was formed by lithiation over x=1.5 in Li_1+xV₃O₈, and the diffusion of lithium in this phase determined the reaction rate of insertion more than x=1.5. Improvement of insertion kinetics in the Li₄V₃O₈ phase extended the lithium insertion limit from x=3.2 to x=4.0, compared with the case of LiV₃O₈ by conventional high temperature synthesis. Lithium insertion proceeds as the single-phase reaction in the range of 3.2<x<4.0.     

Lithium aluminum nitride,Li3AlN2 as a lithium solid electrolyte

Single phase of Li₃AlN₂ was prepared from the mixture of Li₃N/AlN = 1.2 to 1.5 in molar ratio at 700°C and at 900°C. It crystalizes in the cubic system derived from antifluorite-type structure having the lattice parameter $\text{a = 9.470}\text{A}\text{?}$. It is a pure ionic conductor having conductivity of 5 × 10^?8ω^?1cm^?1 at room temperature and an activation energy of 52 kJ/ mol. Its decomposition voltage was 0.85 V at 104°C. The TiS₂/Li₃AlN₂/Li cell could be discharged at a constant current of 45 μA/cm² at 104°C.     

Electronic structure and properties of NbS2 and TiS2 low dimensional structures

Transition metal dichalcogenides have a laminar structure, weakly bound through van der Waals interactions. Due to their technological applications in catalytic processes the bulk structure of many of them has been widely studied in the last 30 years. Some of them, such as NbTe₂ and TiSe₂, show superconductivity and have been, therefore, the subject of intense study. Novoselov et al. (2005 [1]) achieved to isolate not only graphene but also other bidimensional crystals, among them layers of some dichalcogenides. These bidimensional crystals preserve their monocrystallinity under normal ambient conditions, keeping the crystal structure of the bulk. In this contribution we calculate the magnetic and electronic properties of 2D layers of NbS₂ (non-magnetic metal in 3D) and TiS₂ (non-magnetic semimetal in 3D) as well as quasi 1D chains cut out from these layers.     

Electrical transport measurements in TiS3

Results of measurements of conductivity and Hall coefficient in the temperature range 15–300K and of thermal emf in the temperature range 80–400K, carried out on TiS₃ samples, are reported. The results indicate that these crystals are semiconducting with extrinsic n-type conductivity. The mobility of the carriers is about 30 cm²/V sec at room temperature, increases up to about 100 cm²/V sec at 100K and drops at lower temperatures. The Seebeck coefficient is in qualitative agreement with these findings but its detailed temperature dependence is not yet understood.     

Raman spectroscopic analysis of sulphur-doped TiO2 by co-grinding with TiS2

Doping sulphur into titania has been tried using TiS₂ as a doper based on the mechanically induced solid-state reaction between TiO₂ and TiS₂. The prepared samples have been characterized by X-ray diffraction (XRD), Raman spectroscopy and UV-Vis reflectance spectroscopy. Raman analysis, particularly has been proved to be effective in assessing the sulphur doping by correlating the oxygen deficiency of the doped oxide with the change of active Eg mode of rutile phase.     

光学泵浦的锂分子激光

以可见染料激光泵浦锂分子,在高于900℃的蒸气温度下,获得了由理分子A¹∑_u⁺态跃迁到基态X¹∑_g⁺的位于874—912nm区的许多光泵激光输出。谐振腔使输出信号增强约9倍。对部分激光跃迁的振转量子数作了标识。 关键词：     

X-ray study of c-axis parameters in disordered stage II Agχ TiS2

X-ray measurements have been performed on disordered Stage II Ag_χ TiS₂ crystals with χ = 0.18 and 0.19. The c-axis structure was determined using the 00.l reflections for 4 ?l? 29. A principal result is that the intercalation of Ag⁺ between S layers produces unequal TiS distances in the adjacent TiS₂. The charge transfer to the Ti layer produces an expanded TiS distance adjacent to the Ag layer. The TiS distance away from the Ag ions is accordingly contracted. This effective (indirect) repulsive interaction between Ag⁺ and Ti may provide a mechanism for staging in these materials by keeping the Ag layers as far apart as possible.     

Electrochemical determination of the lithium ion diffusion coefficient in TiS2

Long-time chronoamperometry of TiS₂ electrodes immersed in saturated LiClO₄/DMF solution was employed to investigate the charge transport processes which govern the rate of Li⁺ intercalation in TiS₂. The intercalation rate and hence, the current, appears to be controlled by the rate of Li⁺ diffusion within the TiS₂. A model has been developed which predicts the current-time behavior under the control of Li⁺ solid state diffusion. The close agreement of this model with the experimental data allows the solid state diffusion coefficient and other transport parameters (such as effective electrode area) to be evaluated from the measured average grain boundary distance. Typical TiS₂ grain boundary distances in the 3–10 μm range yield a geometric mean value of 1.3 × 10^?9 cm²/s for the solid state diffusion coefficient; this is in close agreement with previously reported diffusivities as measured by NMR spin-lattice relaxation techniques.     

NMR spectral densities and two dimensional diffusion in TiS2(NH3)1.0 and TaS2(NH3)x

NMR measurements of proton spin-lattice relaxation times T₁ and T_1? in the layered intercalation compounds TiS₂(NH₃)_1.0 and TaS₂(NH₃)_x (x = 0.8, 0.9, 1.0) are reported as functions of frequency and temperature (100 K – 300 K). These observations probe the spectral density of magnetic fluctuations due to motions of the intercalated molecules at frequencies accessible to the T₁ (4–90 MHz) and T_1? (1–100 kHz) measurements. Since the average molecular hopping time (τ) can be changed by varying temperature, different regions of the spectral density can be examined. For T > 200 K, both T^?1₁ and T^?1_1? vary logarithmically with frequency, reflecting the two dimensional character of the molecular diffusion. The temperature dependence of T₁ suggests that a more accurate picture of the short time dynamics is required. No dependence of relaxation rate on vacancy concentration is found.     

Electronic structure of Li3GaN2

First principles calculations, by means of the full-potential linearized augmented plane wave method within the local density approximation, were carried out for the electronic properties of Li₃GaN₂. The calculated lattice parameter is in good agreement with the measured one. The bandgap is direct at the Brillouin zone centre. The Li-N and Ga-N bonds are both ionic with a small covalent character of the latter one.     

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：     

Etudes electrique et Raman des verres du systeme B2O3 - Li2O - Li2SO4

New vitreous electrolytes with fast lithium ion carriers have been obtained in the B₂O₃ - Li₂O - Li₂SO₄ system. The variation of the ionic conductivity is discussed. Raman spectroscopy indicates that sulfate ions are diluted in the vitreous matrix without detectable interaction with the surrounding.     

Stacking transformation and defect creation in Cs intercalated TiS2 single crystals

The intercalation of TiS₂ single crystals with Cs was studied by transmission electron microscopy. Evidence was found for an intercalation induced 1T→3R structure transformation. The Cs⁺ ions formed an structure. In the thinnest parts of the crystals, the intercalation induced cracks and moiré fringes. In thicker parts the 1T→3R transformation was frustrated, with formation of intercalation ribbons and dislocation loops. Air exposure resulted in de-intercalation and oxidation of Cs. The results emphasise the connections between defects and intercalation.     

Ion diffusion in the high-temperature phases Li2SO4, LiNaSO4, LiAgSO4 and Li4Zn(SO4)3

Diffusion in the four high-temperature sulphate phases Li₂SO₄, LiNaSO₄, LiAgSO₄ and Li₄Zn(SO₄)₃ was studied extensively some 20–30 years ago. We have now carried out a re-evaluation where we include information obtained from a number of studies of other properties. The data are adjusted slightly due to the use of another type of regression analysis. It is characteristic of the four phases that they are both plastic crystals and solid electrolytes (superionic conductors). The cause of the high conductivity is that the mobility of the cations is strongly enhanced by the rotational motion of the translationally static sulphate ions. This is observed not only for the abundant cations, but also for other cations present (mono- as well as polyvalent) and for monovalent anions. Furthermore, both bulk diffusion and transfer along high diffusivity paths are affected. In addition, one can distinguish between different contributions to the bulk diffusion. The ionic radius is a very important parameter, since it determines the solid solubility and the distribution of the ions between the sites that are available in the lattice. All this affects the relative importance of several competing diffusion mechanisms. This gives a qualitative explanation of an anomalous correlation which has been observed in FCC Li₂SO₄ for monovalent ions (cations as well as anions), namely that both the diffusion coefficients D, and the activation energies Q, decrease when the radius is increased. This holds for hard-core cations (Li, Na, K, Rb), polarizable cations (Ag, Tl) and anions (F, Cl, Br). On the other hand, the situation is normal for divalent cations for which an increase in D corresponds to a decrease in Q. This is the case for hard-core ions (Mg, Ca) as well as for polarizable ones (Zn, Cd, Pb). Migration of the large ions Cs⁺ and SO²⁻₄ appears to be specially sensitive to how the experiment is prepared. Diffusion in BCC LiNaSO₄ and LiAgSO₄ has been studied for the two main cations as well as for some dopant ions. A general conclusion is that studies of diffusion of several ions in the same structure can give information that cannot be obtained by other types of experiments.     

Effects of Li2CO3 on the sintering behavior and piezoelectric properties of Bi2O3-excess (Bi0.5Na0.5)0.94Ba0.06TiO3 ceramics

(Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ ceramics doped with Li₂CO₃ and Bi₂O₃ as sintering aids were manufactured, and their micro structural, dielectric and piezoelectric properties were investigated. All specimens could be well sintered at a low-temperature of 1080 °C. The bulk density of the specimens doped with a small amount of Li₂CO₃ was enhanced. The dielectric and piezoelectric properties of ceramics were investigated with different amounts of Li₂CO₃ substitutions. High electrical properties of d₃₃ = 167 pC/N, k_p = 0.34, P_r = 40 μC/cm² and E_c = 38 kV/cm were obtained from the specimen containing 0.1 mol% of Li₂CO₃ sintered at 1080 °C.     

Electrical and electrochemical properties of glass-ceramic electrolytes in the systems Li2S-P2S5-P2S3 and Li2S-P2S5-P2O5

Electrical and electrochemical properties of the 70Li₂S·(30 − x)P₂S₅·xP₂S₃ and the 70Li₂S·(30 − x)P₂S₅·xP₂O₅ (mol%) glass-ceramics prepared by the mechanical milling technique were investigated. Glass-ceramics with 1 mol% P₂S₃ and 3 mol% P₂O₅ showed the highest conductivity of 5.4 × 10^− 3 S cm^− 1 and 4.6 × 10^− 3 S cm^− 1, respectively. Moreover, these glass-ceramics showed higher electrochemical stability than the 70Li₂S·30P₂S₅ (mol%) glass-ceramic. From the XRD patterns of the obtained glass-ceramics, trivalent phosphorus and oxygen were incorporated into the Li₇P₃S₁₁ crystal. We therefore presume that the Li₇P₃S₁₁ analogous crystals, which were formed by incorporating trivalent phosphorus and oxygen into the Li₇P₃S₁₁ crystal, improve the electrical and electrochemical properties of the glass-ceramics. An all-solid-state cell using the 70Li₂S·29P₂S₅·1P₂S₃ (mol%) glass-ceramic as solid electrolyte operated under the high current density of 12.7 mA cm^− 2 at the high temperature of 100 °C. The cell showed an excellent cyclability of over 700 cycles without capacity loss.