A new layered type compound, HTaWO 6·nH 2O (n=0.5−1.5) prepared from LiTaWO 6 by ion exchange reaction

Abstract

A layered type compound HTaWO 6·nH 2O (n=0.5–1.5) was prepared from LiTaWO 6 by ion exchange reaction in acid solutions. X-ray powder diffraction patterns of HTaWO 6·nH 2O were indexed with tetragonal cells similar to that of the starting material, although the c-axes were almost doubled. The lattice parameters were a=4.70 and c=21.0 A ̊ for n=0.5. The length of the c-axis and degree of hydration of HTaWO 6·nH 2O were dependent on relative humidity. Two steps of dehydration were observed on heating of HTaWO 6·0.5H 2O; HTaWO 6 and TaWO 5.5 were produced at the first and second steps, respectively. Both dehydrated phases retained the tetragonal system. TaWO 5.5 was finally transformed to the tetragonal bronze type structure via an intermediate phase at an elevated temperature. A reverse ion exchange reaction yielded Li 0.9H 0.1TaWO 6·H 2O. The behavior of HTaWO 6·nH 2O coincides with that of typical layered compounds, then the compound and also the starting material, LiTaWO 6, are considered to have layered structures.