Structural phase transition and crystal structure of a highly deuterated (ND4)3D(SeO4)2 crystal

Differential scanning calorimetric, dielectric, electrical conductivity and X-ray diffraction measurements have been performed on a highly deuterated triammonium hydrogen diselenate (ND4)(3)p(SeO4)(2) crystal. It is found that this deuterated crystal undergoes four phase transitions at 231, 282, 304 and 328 K, and phase III, which was not detected in our previous studies on other deuterated crystals, exists between 282 and 304 K. The crystal structures of phases I, II and III are determined. The isotope effect on O-H-O hydrogen bonds by the substitution of deuterium for hydrogen is discussed. (C) 2003 WILEY-VCH Veflag GmbH & Co. KGaA, Weinheim.