POROUS GLASS-CERAMICS COMPOSED OF A TITANIUM PHOSPHATE CRYSTAL SKELETON - A REVIEW

Bulk microporous glass-ceramics with a skeleton of two types of functional titanium phosphate crystal were prepared by controlled crystallization of RTi(2)(PO4)(3) (R = Li, Na, 1/2Ca)-Ca-3(PO4)(2) glasses, and chemical treatment. One crystal is a NASICON-type with a three-dimensional network structure of TiO6 and PO4 while the other is a zirconium phosphate-type crystal Ti(HPO4)(2) . 2H(2)O with a two-dimensional layered structure. The mean pore diameter and porosity of 30-60 nm and 40-60 vol.% were achieved. Porous CaTi4(PO4)(6) glass-ceramics have excellent properties as supports for immobilization of enzymes, humidity sensors and porous LiTi2(PO4)(3) glass-ceramics as ion exchange media. Conspicuous bacteriostatic activities were found for the partially Ag-exchanged porous LiTi2(PO4)(3) and Li1.4Ti1.6Al0.4(PO4)(3). Integrated microporous glass-ceramics with skeletons of LiTi2(PO4)(3) (LTP) and Ti(HPO4)(2) . 2H(2)O (TP) crystals were synthesized utilizing a novel discovery that LTP is transformed into TP in acid solution.