Structure of lithium iodate - iodic acid solid solution Li1-xHxIO3 (x = 0.33)

Raman study of crystals

“…A series of measurements were performed after turning the sample by 60 • around the caxis. The results obtained using different scattering geometries were found to be absolutely invariant under this symmetry operation, in accordance with the x-ray and neutron results [7], which proposed a hexagonal symmetry structure.…”

“…Crystals of good optical quality were obtained with dimensions of about 2 × 2 × 5 mm. The concentration x of protons in each sample was obtained from the determination of the lattice parameters c and a, using the relation proposed by Le Roy et al [7], which relates x to the ratio c/a. The coordinate system used in the Raman experiments is such that z is the hexagonal axis, x is perpendicular to z and parallel to a natural face of the crystal, and y is perpendicular to x and z.…”

“…This result led them to conclude that the solid solutions could not be isomorphous with α-LiIO 3 . However, in 1990, Le Roy et al [7] determined the room temperature structure of Li 1−x H x IO 3 (x = 0.33) by x-ray singlecrystal and neutron powder diffraction, and concluded that it presents a hexagonal average symmetry, belonging to the same C 6 6 (P 6 3 ) space group as α-LiIO 3 . Figure 1 shows the crystal structure of the hydrated solid solution as determined in reference [7].…”

“…However, in 1990, Le Roy et al [7] determined the room temperature structure of Li 1−x H x IO 3 (x = 0.33) by x-ray singlecrystal and neutron powder diffraction, and concluded that it presents a hexagonal average symmetry, belonging to the same C 6 6 (P 6 3 ) space group as α-LiIO 3 . Figure 1 shows the crystal structure of the hydrated solid solution as determined in reference [7]. Note that the protons do not replace the lithium ions, but are randomly distributed in general positions between two oxygen atoms belonging to different iodate groups, with an occupation factor of 0.33.…”

“…In order to elucidate why the previous Raman studies [5,6] and the neutron and x-ray results [7] are at variance, a complete polarized Raman study of Li 1−x H x IO 3 single crystals for several values of x (x 0.36) was performed, using different scattering geometries. The results and their analysis are presented in the following.…”