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Abstract: Electrical properties and 1H-NMR absorption line have been measured, in order to investigate proton dynamics in a superionic phase in Tl3H(SO4)2. From the measurement of the thermoelectric power, it is found that a majority carrier in electrical conductivity is a proton. Moreover, from 1H-NMR measurement it is also found that the activation energy 0.33eV of the hopping motion of protons is close to 0.38eV as observed in the electrical conductivity measurement. These results indicate that the electrical conductivity in the superionic phase is caused by the hopping motion of protons accompanied by the breaking of the hydrogen bonds. [Copyright &y& Elsevier]

The structure of thallium selenate, Tl2SeO4, in a paraelastic phase (above 661 K) has been analysed by Rietveld analysis of the X-ray powder diffraction pattern. Atomic parameters based on the isomorphic K2SO4 crystal in the paraelastic phase were used as the starting model. The structure was determined in the hexagonal space .group P63/mmc, with a = 6.2916 (2) Å and c = 8.1964 (2) Å. From the Rietveld refinement it was found that two orientations are possible for the SeO4 tetrahedra, in which one of their apices points randomly up and down with respect to [001]. One Tl atom lies at the origin with &3macr;m symmetry, the other Tl and one of the O atoms occupy sites with 3m symmetry, the Se atom is at a site with &6macr;m2 symmetry and the remaining O atom is at a site with m symmetry. Furthermore, it was also found that the TI atoms display anomalously large positional disorder along [001] in the paraelastic phase. [ABSTRACT FROM AUTHOR]

The structure of trithallium hydrogen bis­(sulfate), Tl3H(SO4)2, in the super-ionic phase has been analyzed by Rietveld analysis of the X-ray powder diffraction pattern. Atomic parameters based on the isotypic Rb3H(SeO4)2 crystal in space group R m in the super-ionic phase were used as the starting model, because it has been shown from the comparison of thermal and electric properties in Tl3H(SO4)2 and M3H(SO4)2 type crystals ( M = Rb, Cs or NH4) that the room-temperature Tl3H(SO4)2 phase is isostructural with the high-temperature R m-symmetry M3H(SO4)2 crystals. The structure was determined in the trigonal space group R m and the Rietveld refinement shows that an hydrogen-bond O-­H⋯O separation is slightly shortened compared with O-H⋯O separations in isotypic M3H(SeO4)2 crystals. In addition, it was found that the distortion of the SO4 tetrahedra in Tl3H(SO4)2 is less than that in isotypic crystals. [ABSTRACT FROM AUTHOR]

The structure of thallium selenate, Tl2SeO4, in a paraelastic phase (above 661 K) has been analysed by Rietveld analysis of the X-ray powder diffraction pattern. Atomic parameters based on the isomorphic K2SO4 crystal in the paraelastic phase were used as the starting model. The structure was determined in the hexagonal space group P6(3)/mmc, with a = 6.2916 (2) A and c = 8.1964 (2) A. From the Rietveld refinement it was found that two orientations are possible for the SeO4 tetrahedra, in which one of their apices points randomly up and down with respect to [001]. One Tl atom lies at the origin with 3m symmetry, the other Tl and one of the O atoms occupy sites with 3m symmetry, the Se atom is at a site with 6m2 symmetry and the remaining O atom is at a site with m symmetry. Furthermore, it was also found that the Tl atoms display anomalously large positional disorder along [001] in the paraelastic phase.