The effect of K+ ion exchange on the structure and thermal reduction of hexagonal ammonium tungsten bronze

This paper discusses the changes in the structure and thermal reduction of nanosize hexagonal ammonium tungsten bronze (HATB), (NH4)(0.33-x)WO3-y, which were caused by K+ ion exchange (doping) and studied by XRD, XPS, H-1-MAS NMR, FTIR, SEM and TG/DTA-MS. Comparison of the cell parameters of undoped and doped HATB revealed that both a and c cell parameters decreased after the ion exchange reaction, which showed that smaller K+ ions partly replaced the larger NH (4) (+) ions in the hexagonal channels of HATB. After the reaction, from the hexagonal channels less NH3 evolved, which also supported the incorporation of K+ ions into the hexagonal channels.