Cesium hydrogen sulphate CsHS04 and cesium hydrogen selenate CsHSe04 are pseudo-one-dimensional hydrogen bonded systems /1, 2/ with a structure resembling that of CsH2P04 in the paraelectric phase apart from the extra hydrogen in CsH2P04 /l/. At room temperature CsHS04 belongs t o the monoclinic space group P21/m with a = 7.304 8 , b = 5.810 8 , c = 5. 491 %, @ = = 101 .51° and two formula units per unit cell /1/ (Fig. 1). Separate chains of 0 -H --0 bonded SO4 groups run along the b-axis /l/. The length of the 0-H--0
The diffusion of protons in the superionic phase of CsHSO4 was investigated by quasielastic neutron scattering (QNS) on the IRIS spectrometer at the pulsed spallation neutron source ISIS, Rutherford Appleton Laboratory, UK. Two processes with different characteristic times could be distinguished: long-range translational diffusion with a diffusion coefficient D=(1.00-1.17)*10-7 cm2 s-1 (for a temperature range from 423 to 448 K) and jump rotation of HSO4 groups between two possible orientations, the corresponding nonequivalent proton sites being 2.3 AA apart.
A method of visualizing the 18O"-domain structure in TGS type crystals by means of nematic liquid crystals (NLC) is described. The possibility of visualization is due to the different orientation of NLC molecules on the domains with opposite orientation. The method enables the observation of static domain structure on cleaved surfaces of TGS and domain dynamics on polished and etched surfaces. The temperature and DC-field dependences of domain motion are similar to those previously revealed by indirect methods. The AC-dependences of domain nucleation and sideward motion of domain walls are shown to be quite different in TGS crystals grown in the paraelectric and ferroelectric phases. In the latter the existence of a row structure of centres of nucleation was observed which do not coincide with growth layers.
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