Neutron structure refinement of γ- and β-lithium lodate: Comparison between α, γ, and β phases

Synthesis, Characterization, and Crystal Structure Determination of a New Lithium Zinc Iodate Polymorph LiZn(IO3)3

Synthesis and characterization of anhydrous LiZn(IO3)3 powders prepared from an aqueous solution are reported. Morphological and compositional analyses were carried out by using scanning electron microscopy and energy-dispersive X-ray measurements. The synthesized powders exhibited a needle-like morphology after annealing at 400 °C. A crystal structure for the synthesized compound was proposed from powder X-ray diffraction and density-functional theory calculations. Rietveld refinements led to a monoclinic structure, which can be described with space group P21, number 4, and unit-cell parameters a = 21.874(9) Å, b = 5.171(2) Å, c = 5.433(2) Å, and  = 120.93(4)°. Density-functional theory calculations supported the same crystal structure. Infrared spectra were also collected, and the vibrations associated with the different modes were discussed. The non-centrosymmetric space group determined for this new polymorph of LiZn(IO3)3, the characteristics of its infrared absorption spectrum, and the observed second-harmonic generation suggest it is a promising infrared non-linear optical material.

Martensitic α↔γ Phase Transition and Ionic Conductivity in "Pure" and Doped LiIO3 Single Crystals

The polymorphism and anisotropy of electrical, dielectric, and thermophysical properties of “pure” and doped LiIO3 single crystals are studied. The hexagonal a-LiIO3 phase is a 1-D ionic conductor (along the c axis). The anisotropy of the ionic conductivity of the a-phase can be reduced by doping with transitive metals (Fe, Mo, Ni). The martensitic character of the a«g transition is proved. In the γ-phase, only a slight anisotropy of the conductivity is found. The a«g transition is not an ionic-superionic one.

51V magic-angle-spinning NMR and electric field gradient calculations in V2O5 and gamma-LiV2O5 crystals

51V Magic-angle-spinning (MAS) NMR has been applied to V2O5 at two different magnetic field strengths (4.7 and 7.1 T). Both the magnitude and relative orientation of the quadrupole and chemical shift (CS) tensors have been determined by iterative fitting of the 51V MAS NMR lineshapes at the two magnetic field strengths. The reliability of the results is discussed. Moreover, it is shown that previous low-field single-crystal data are fully consistent with the high-field powder-sample MAS NMR results provided that a slight noncoincidence between the CS tensor and the crystal frame axes is considered. The electric field gradient tensor at the vanadium and lithium sites is subsequently used to test several electronic structure calculation at an ab initio Hartree-Fock level in V2O5 and gamma-LiV2O5 crystals. It is shown that a wide distribution of oxygen charges must be considered to describe the particular environment of each type of oxygen atoms. Furthermore, this analysis supports the fact that the vanadyl bond is likely a short ionic bond. NMR is found to be a valuable experimental tool to get insight into the nature of chemical bonds in vanadium oxides.