Ion exchange of HTaWO 6·nH 2O (n = 0.5−1.5) with a layered structure

Abstract

Ion exchange of HTaWO 6·nH 2O having a layered structure was attempted with the alkaline ions (Na +, K +, Rb + and Cs +). X-ray powder patterns of ion exchanged compounds were indexed with tetragonal cells similar to that of HTaWO 6·nH 2O, the c-axes are almost doubled when compare with that of LiTaWO 6, the starting material for the preparation of HTaWO 6·nH 2O. The degree of ion exchange and the length of the c-axis were dependent on ionic radii of alkaline ions. The layered structure remained unchanged after complete dehydration to A xTaWO 5.5 + x/2, and finally a tetragonal bronze type phase for A=Na or a hexagonal bronze type phase for A=K, Rb and Cs appeared at elevated temperatures. These differences with alkaline ions are discussed in terms of ionic radius.