Structural, conductivity and dielectric studies in (NH4)2SeO4•Te(OH)6

The compound (NH4)(2)SeO4 center dot Te(OH)(6) crystallizes in the monoclinic P2(1)/c space group. It was analyzed at room temperature using X-ray diffractometer data. The molecular species present in the lattice are Te(OH)(6) octahedra and SeO4 tetrahedra arranged in a number of planes parallel to the be plane. The thermal analysis of the title compound shows three distinct endothermal peaks at 415,433 and 443 K. The evolution of the dielectric constant as a function of frequency and temperature revealed one anomaly at about 433 K attributed to a ferro-paraelectric phase transition. However, the evolution of the conductivity versus temperature showed the presence of a super-ionic-protonic phase transition at 443 K. (c) 2004 Elsevier B.V. All rights reserved.