Structure and ion-exchange properties of tungsten-antimony crystalline acid and its substituted forms

The studies of the structural transformations of tungsten-antimony crystalline acid (TACA) during ion exchange and thermolysis of its substituted M$^+$-, H$^+$-forms (M$^+$ — Li, Na, K, Ag) are carried out. It was shown that hydrated TACA compounds containing monovalent metal ions are stable up to 1020 K with pyrochlore-type structure (space group Fd-3m). Using Rietveld method, the structural characteristics of TACA and its M$^+$-, H$^+$-forms were refined, and a model of crystallographic positions filling with metal ions for pyrochlore-type structure was proposed. Using methods of thermogravimetry, X-ray diffraction and IR spectroscopy, a correlation between the composition of the obtained compounds, structural disorder, and their ion-exchange properties was determined.