PREPARATION AND IONIC-CONDUCTIVITY OF ALKALI-METAL TITANIUM SILICOPHOSPHATES AXTI3P6SI2O25 (A=LI, NA, K)

A new series of alkali ion conductors AxTi3P6Si2O25 (A = Li, Na, K; 0 less-than-or-equal-to x < 2) has been derived from KTi3P6Si2O25 by means of a deintercalation-intercalation technique. K+ ions were deintercalated from KTi3P6Si2O25 by the reaction with Cl2 gas as a oxidizing agent and new compound Ti3P6Si2O25 was prepared. Lithium and sodium ions were intercalated into this new compound using n-butyl lithium and Na-naphthalene/THF. Potassium ions were not intercalated into Ti3P6Si2O25 but into KTi3P6Si2O25 using K-naphthalene/THF. Lithium intercalation sample Li1.35Ti3P6Si2O25 showed the highest conductivity of 3.4 x 10(-4) S cm-1 at 400-degrees-C with the lowest activation energy of 0. 56 eV. A large difference in activation energy for alkali ion conduction in this crystal was explained by comparison of size of bottleneck and that of alkali ions.