A new type of PbHNSO 3 crystal has been grown by a gel method using agar-agar gel. TG-DTA and X-ray diffraction measurements have been performed on single crystal samples of PbHNSO 3 . It is found that the thermal decomposition of the compound starts at about 960 K. The space group (orthorhombic Pnma) and structural parameters are determined at room temperature with unit cell dimensions: a=8.4690(6), b=5.3934(4) and c=6.9530(4) Å. The crystal structure is found to consist of NSO 3 pseudo-tetrahedra, PbO 9 N 3 polyhedra, and NSO 3 -Pb-NSO 3 frameworks. The dark brown color of the crystal is suggested to be caused by the absorption of blue wavelengths of light which is due to the excitation of excess electrons in potential wells produced by the NSO 3 -Pb-NSO 3 framework.

DSC, TG-DTA and X-ray diffraction measurements have been performed on cesium hydrogen selenate CsHSeO 4 and deuterated CsDSeO 4 crystals. The superionic phase transitions for the proton and deuterated compounds were found to occur at 402.6 and 398.1 K, respectively. The thermal decomposition accompanied by hydrolysis in both compounds started at around the transition temperature, and the maximum rate of weight loss from the reaction was observed at around 490 K. The space group symmetry (monoclinic P2 1 /c) and structural parameters were determined at 298 and 355 K. The expansion of the O-H-O hydrogen bond at room temperature by the substitution of deuterium for hydrogen was observed to be 0.015(7) Å. The geometric isotope effect on the hydrogen bond structure by deuteration was realized in the CsHSeO 4 crystal. The experimental results denied the existence of a phase transition from phase II to III in the proton and deuterated compounds.