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Lithium titanium orthophosphate LiTi2(PO4)3 (LTP) has attracted attention as a chemically stable fast Li+-conductor in ambient atmosphere. It was reported in our previous paper7 that monolithic microporous glass-ceramics with a skeleton of this crystal were successfully prepared from glasses in the pseudobinary system of LTP and Ca3(PO4)2. Here we report that these porous glass-ceramics (mean pore diameter: ∼40 nm; total specific surface area: ∼30 m2; porosity: ∼45 vol.%) show excellent cation exchange properties. Approximately 50% of Li+ ions in the materials are exchanged with monovalent ions with ionic radii smaller than 130 ppm in 1 h at room temperature. In particular, Li+ ions are selectively exchanged with Ag+ ions even in the presence of Na+ ions. The exchange rate in the porous glass-ceramics is larger by two orders of magnitude than that of sintered LTP. The ratio of these exchange rates is close to that of the total surface areas, indicating that most of the pores in porous LTP glass-ceramics are available for ion exchange reactions. These are the first porous glass-ceramics having excellent cation exchange properties.

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Lithium titanium phosphate LiTi2(P04)3 has been found to have excellent cation-exchange properties. Lithium ions readily exchange with Na § and Ag § at room temperature but do not with other monovalent ions and divalent ions. Bulk microporous ceramics composed of a skeleton of LiTi2(P04)3 and continuous pores have been prepared by a controlled crystallization of glasses in the pseudobinary LiTJ2(P04) 3-Ca3(P04) 2 system and subsequent leaching of Ca3(PQ4)~ phases with acids. The resulting porous LiTi2(P04)3 ceramics have a porosity of -4 5 volume percent, a median pore diameter of 60 nm (full width at half maximum of the pore size distribution --30 nm), and a specific surface area of -3 0 m 2. This is the first cation exchangeable material fabricated via glass-ceramic process, to our knowledge.