ION-EXCHANGE REACTION OF A-SITE IN A2Ta2O6 PYROCHLORE CRYSTAL STRUCTURE

Na+ or K+ ion rechargeable battery is started to garner attention recently in Place of Li+ ion cell. It is important that A+ site ion can move in and out the positive-electrode materials. When K2Ta2O6 powder had a pyrochlore structure was only dipped into NaOH aqueous solution at room temperature, Na2Ta2O6 was obtained. K2Ta2O6 was fabricated from a tantalum sheet by a hydrothermal synthesize with KOH aqueous solution. When Na2Ta2O6 was dipped into KOH aqueous solution, K2Ta2O6 was obtained again. If KTaO3 had a perovskite structure was dipped, Ion-exchange was not observed by XRD. Because a lattice constant of pyrochlore structure of K-Ta-O system is bigger than perovskite, K+ or Na+ ion could shinny through and exchange between Ta5+ and O2- ion site in a pyrochlore structure. K+ or Na+ ion exchange of A(2)Ta(2)O(6) pyrochlore had reversibility. Therefore, A(2)Ta(2)O(6) had a pyrochlore structure can be expected such as Na+ ion rechargeable battery element.