Inorganic Chemistry, Vol.51, No.13, 7317-7323, 2012
Exploration of Mid-Temperature Alkali-Metal-Ion Extraction Route Using PTFE (AEP): Transformation of alpha-NaFeO2-Type Layered Oxides into Rutile-Type Binary Oxides
Alkali-metal-ion extraction reactions using poly(tetrafluoroethylene) (PTFE; AEP reactions) were performed on two kinds of alpha-NaFeO2-type layered compounds: Na-0.68(Li0.68/3Ti1-0.68/3)O-2 and K-0.70(Li0.70/3Sn1-0.70/3)O-2. At 400 degrees C in flowing argon, these layered compounds were reacted with PTFE. By these reactions, alkali-metal ions in the layered compounds were successfully extracted, and TiO2 and SnO2 with rutile-type structure were formed. The structural similarity between the alkali-metal-ion-extracted layered compounds and the binary metal oxide products in these unique alkali-metal-ion extraction reactions was interpreted in terms of their interatomic distance distribution by atomic pair distribution function analysis. The results of this study indicate that PTFE is an effective agent to extract alkali-metal ions from layered compounds, and AEP reaction is not limited to the previously reported gamma-FeOOH-type layered titania K-0.8(Li0.27Ti1.73)O-4, but is also applicable to other layered titania and other non-titanium-based layered metal oxides. Therefore, it was clarified that AEP reactions are widely applicable routes to prepare various compounds, including those that are difficult to synthesize by other reactions.