H. D. Lutz

Lattice vibration spectra. LIX. Single crystal infrared and Raman studies of spinel type oxides

Abstract The infrared reflection and Raman spectra of spinel type oxides M Cr 2 O 4 ( M = Mg, Mn, Fe, Co, Ni, Cu, Zn), M Fe 2 O 4 ( M = Ni, Cu), and Mn 3 O 4 (single crystals, pressed pellets) including Kramers-Kronig analyses and oscillator-fit calculations are presented. The spectra are discussed with respect to the true space group and ionicities of these compounds as well as the vibrational modes, phonon energies, and resonance Raman effects compared with the respective spectra of spinel type halides, sulfides, and selenides. Because of the relatively high porosity of the pellets obtainable the true frequencies of the IR allowed phonons can only be determined from single crystal spectra.

Lattice vibration spectra: XLVIII. Infrared and Raman studies of spinel-type fast lonic conductorsLi2MCl4 (M =Mg, V, Cr, Mn, Fe, Co, Zn, Cd) and Li2MnBr4

Abstract The Raman and infrared reflection spectra of the spinel-type halidesLi 2 M II Cl 4 ( M II = Mg, V, Cr, Mn, Fe, Co, Zn, Cd) and Li 2 MnBr 4 including Kramers-Kronig analyses and oscillator-fit calculations are presented. These results are discussed in terms of (i) fast ionic conductivity, (ii) cation distribution, i.e., normal (Li 2 ZnCl 4 ) and inverse spinels, 1:1 ordering of Li and M II in the octahedral sites (Li 2 CoCl 4 ), (iii) phase transitions to an ordered (LiVo 2 type) and disordered NaCl defect structure, and (iv) two-mode behavior of the phonon modes.

Structure refinement of pyrite-type ruthenium disulfide, RuS2, and ruthenium diselenide, RuSe2

RuS 2 cristallise dans Pa3 - avec a=5,6106 A, Z=4; affinement jusqua R=0.021. RuSe 2 cristallise dans Pa3 - avec a=5,9336 A, Z=4; affinement jusqua R=0,021. Les distances intermoleculaires des agregats S 2 et Se 2 sont beaucoup plus petites que les sommes des rayons de Van der Waals correspondantes. La longueur de la liaison Se−Se intraionique de RuSe 2 est proche de la somme des rayons covalents pour la forme quadratique; la distance S−S correspondante de RuSe 2 est plus petite que celle basee sur les rayons covalents

Ionic conductivities of spinel-type quaternary lithium chlorides-phase diagrams of LiClMIClMIICl2 (MICu, Na; MIIMn, Cd, Mg)

Abstract The phase relationships of the systems Li2MIICl4ue5f8M2IMIICl4 (MIue5fbCu, Na; MIIue5fbMg, Mn, Cd) were studied by thermal analyses (DTA), X-ray and Raman methods. The electric conductivities of the Li2−2xM2xIMIICl4 solid solutions obtained were determined by impedance spectroscopy. In the ternary Li2MIICl4 as much as 100 mol% of lithium can be replaced by copper (I) (at 650 K, MIIue5fbCd) and 80 mol% by sodium (at 720 K). At ambient temperature, the mutual solubilities are considerably smaller, i.e., negligible for MIue5fbNa and only up to 40 mol% for MIue5fbCu. In case of the copper containing compounds, the transitions of the spinel-type solid solutions present at ambient temperature to deficient NaCl superstructures at elevated temperatures can be studied by both X-ray and Raman methods. The ionic conductivities of the solid solutions decrease (i) slightly with increase in sodium content, but (ii) strongly with increasing copper content at least for x

Phase relationships of the lithium halide spinels Li2MCl4-Li2MBr4 with M = Mn, Fe, Cd

Abstract The sections Li 2 M Cl 4−4x Br 4x of the quaternary systems LiCl-LiBr- M Cl 2 - M Br 2 with M = Mn, Cd, and Fe were studied by high-temperature X-ray diffraction patterns and DTA and DSC measurements. In the quasibinary lithium manganese halide system complete series of solid solutions exist between the inverse spinels Li 2 MnCl 4 and Li 2 MnBr 4 . Li 2 MnBr 4 and solid solutions with x > 0.54 undergo phase transitions to tetragonal spinels at lower temperatures. In the nonquasibinary system with M = Cd, only at temperatures near 400°C a complete series of mixed crystals is formed. At lower temperatures the system is mainly two-phase with rock salt-type Li 1− y Cd 0.5 y Cl 1− x Br x and cadmium chloride-type Cd 1− y Li 2 y Cl 2−2 x Br 2 x solid solutions in equilibrium. The lithium iron halide system is similar to that of cadmium, but spinel-type Li 2 FeBr 4 does not exist at any temperature. The manganese and cadmium halide spinels and spinel solid solutions undergo phase transitions to NaCl defect structures at elevated temperatures.

The systems CuCl-MIICl2 (M=Mn, Cd), crystal structures of Cu2MnCl4 and γ-CuCl

The phase relationships of the quasibinary systems CuCl-MIlClz (Mil = Mn, Cd) were studied by high-temperature X-ray methods and difference thermal analyses (DTA). Four phases have been established: CdClz-type MY-xCuzxClz and iX-Cui-type Cu _yMg.5yCl solid solutions (above 361 and 321 C C, respectively), and fJ- and y-CuCl with negligible solubility for MH. The phase widths of the Cd containing compounds are 0 10-1 Q-I cm-I above 3500C.

Fast ionic conductivity of ternary iodides in the systems LiIMIII2 (MIIMn, Cd, Pb)

Abstract The phase relationships and electric conductivities of the ternary iodide systems LiIue5f8M II I 2 (M II ue5fbMn, Cd, Pb) have been studied by high-temperature X-ray measurements and impedance spectroscopy methods. Whereas mutual solubility of LiI and MnI 2 is negligible at any temperature deficient NaCl-type mixed crystals Li 1− x M 0.5 x II I (M II ue5fbMn, Cd, Pb) are formed at temperature above 540 K, which, however, cannot be quenched to ambient temperature. The solid solutions obtained exhibit high ionic conductivity, e.g. 1×10 −1 , 3×10 −2 and 7×10 −2 Ω −1 cm −1 at 570K for materials like Li 2 CdI 4 , Li 2 PbI 4 , and Li 4 PbI 6 , respectively.

Li2ZnI4: A neutron powder study

Abstract The crystal structure of Li 2 ZnI 4 was determined by means of neutron powder diffraction studies at 298 K. The olivine-type structure (space group Pnma , Z = 4, a = 1480.3(9), b = 856.0(2), c = 701.2(1) pm) was refined by the Rietveld method to a final R I = 5.48%. In a nearly ideal hexagonal close-packed iodide ion arrangement, Li is located in octahedral, and Zn, in tetrahedral voids, respectively. Apart from the Znue5f8I distances, which are significantly shortened, the bond lengths obtained are as expected from the crystal radii.

Dynamics of lithium ions in spinel-type 7Li2MnCl4

Abstract In order to determine the mechanism of the high ionic conductivity of inverse spinel-type Li 2 MnCl 4 , quasielastic neutron scattering measurements (incident wavelength 0.418 nm) of a 7 Li 2 MnCl 4 single crystal as a function of temperature (360, 428 and 552 K), and momentum transfer Q have been performed. The observed quasielastic intensity depends on temperature but hardly not on Q within the accessible range from 3.0 to 19.5 nm −1 . In particular, there is no indication for anisotropic behaviour. The data is interpreted as local motion of the lithium ions. The long-range translational motion of lithium ions causing the ionic conductivity takes place on a much longer time-scale and cannot be resolved under the present experimental conditions.

The quaternary systemsMSCr2S3In2S3(M =Mn, Fe, Co)

Abstract The phase diagrams of the quaternary systems M Cr 2 S 4 MIn 2 S 4 Cr 2 S 3 In 2 S 3 ) (M =Mn, Fe, Co, (Cd, Hg)) have been studied by X-ray phase analyses and FIR spectra of quenched samples. At temperatures above 1200, 1200, and 1330 K, spinel-type solid solutions(1 − y )Cr 2−2 x In 2 x S 3 − y MS are formed in a large range of compositions. Two-phase regions are only the regions near Cr 2 S 3 and between M S and M (Cr, In) 2 S 4 . At lower temperatures, the spinel-type solid solutions (except M =Cd and Hg) decompose to Cr-rich and In-rich compounds. The sections with constant y show more or less nonquasibinary behavior. Thus, cobalt is enriched in the Cr-rich solid solutions. The phase width of Cr 2 S 3 with respect to M content is 2.5 mole% for M =Co, but it is negligible for M =Mn and Fe.