Effect of homovalent (I−Br−) ion substitution on the ionic conductivity of LiI1−x Brx systems

The study of electric conductivity in the whole range of compositions of mixed LiI_1?x Br_x crystals has shown that doping of pure lithium halide (LiI or LiBr) by homovalent substitution leads to an increase in conductivity. This enhancement is essentially pronounced in the solid solution domains near the compositions of pure compounds (x < 0.15 and x > 0.90). Maximum conductivity is attained for the two phase composition LiI_0.75Br_0.25 (5 × 10^?7 S cm^?1 at 293 K) compared to those of starting compounds (4 × 10^?8: LiI and 9 × 10^?9: LiBr at 293 K). An Arrhenius behaviour of the conductivity evolution versus the inverse of the temperature shows that variations in conductivity are related to those of the activation energy whose minimum is close to 8.7 Kcal mole^?1. Lattice strain involved by substituting anions of different raddi could be the factor which increase the defect population.     

Study of structural and electronic transport properties of Ce-doped LaMnO3

The structural and electronic transport properties of La_1−x Ce _x MnO₃ (x=0.0–1.0) have been studied. All the samples exhibit orthorhombic crystal symmetry and the unit cell volume decreases with Ce doping. They also make a metal-insulator transition (MIT) and transition temperature increases with increase in Ce concentration up to 50% doping. The system La_0.5Ce_0.5MnO₃ also exhibits MIT instead of charge-ordered state as observed in the hole doped systems of the same composition.     

Ionic conductivity of and Raman spectroscopy investigation in binary oxosalts (1 − x)AgPO3xAg2SO4 glasses

(1 ? x)AgPO₃xAg₂SO₄ homogeneous glasses obtained by quenching of a melt of the two salts are pure ionic Ag⁺ conductors. The RT conductivity is increased from 2.5 × 10^?7 to 4 × 10^?6 (Ω cm)^?1 when the ratio of Ag₂SO₄ is increased from 0 to 0.3. Raman spectroscopy shows that no modifications of the (PO₃)^∞ chain skeleton occur by adding Ag₂SO₄. The low-frequency Raman band lying at about 55 cm^?1 is quantitatively correlated to Ag⁺ oscillations, the hopping distance decreasing from 3.0 to 2.7 Å if a jump process between regular Ag⁺ sites is considered.     

Synthese,structure cristalline et analyse vibrationnelle de l'hexathiohypodiphosphate de lithium Li4P2S6

The crystalline compound Li₄P₂S₆ is obtained either by devitrification of Li₄P₂S₇ glass at 450°C with sulfur formation or by crystallisation at 450°C of a Li₂S, P and S melt. The structure determination has been solved by X-ray diffraction on a monocrystal. The unit cell is hexagonal $\text{P6}{}_3\text{mcm}$ with a = 6.070(4), c = 6.577(4) Å, V = 209 ų, Z = 1. Intensities were collected at 293°K with Kα (λ = 0.71069 Å) Mo radiation on an automatic Nonius CAD-4 diffractometer. The structure was solved under the assumption of random disorder of P atoms over two sites (occupancy factor of 0.5). Anisotropic least-squares refinement with W = 1 gave R = 0.047 for 90 independent reflections and 9 variables. The structure is built according to an ABAB sequence sulfur packing. Per unit cell, four out of six octahedral sites are occupied by Li ions, and the other two are statistically filled (0.5) by PP pairs. The PP central bond (2.256(13) Å) links two staggered PS₃ groups (PS = 2.032(5) Å) to form the D_3d symmetry P₂S^4?₆ anion. Infrared and Raman spectra show features very similar to those of Na₄P₂S₆, 6H₂O and M^IIPS₃ compounds. A new assignment in terms of symmetry species is proposed for the P₂S₆ internal modes, which is confirmed by a normal coordinate calculation using a valence force field; the stretching force constants f_PP and f_PS are equal to 1.6 and 2.7 mdyne Å^?1, respectively.     

Preparation and electrical properties of the 0,37Li2S-0,18P2S5-0,45LiI glass

A new lithium vitreous electrolyte has been found in the LiI---Li₂S---P₂S₅ system. LiI concentration in the glass, 45% moles, is close to the solubility limit of LiI in 2Li₂S---P₂S₅ glass.The activation energy is of the order of 7.2 Kcal.mole⁻¹ and the conductivity value is 10⁻³ (ohm cm)⁻¹ at 25°C. The conduction is ionic and assured by Li⁺ ions.     

Two connected inverse spectral transforms

We establish a transformation which connects the potentials of the one-dimensional Dirac and Klein-Gordon operators. This transformation links the solutions of the nonlinear evolution equations solvable by means of the two inverse spectral transforms which use the Dirac and Klein-Gordon direct and inverse spectral problems.