INVESTIGATION OF THE GLASS CRYSTAL TRANSITION OF NA5TI(PO4)3

Na5Ti(PO4)3 can exist in both crystalline and vitreous forms. The glass-crystal transition was investigated using several techniques. The crystallization process involves two steps corresponding to the successive formation of Na4TiO(PO4)2 and Na5Ti(PO4)3 crystals. The latter new phosphate belongs to the Nasicon-type family (a(h) = 9.061 +/- 0.002 angstrom, c(h) = 21.734 +/- 0.004 angstrom, space group R32). Its structure can be described as a three-dimensional framework containing TiO6 and NaO6 octahedra sharing common comers with the PO4 tetrahedral groups. The titanium and sodium atoms are distributed with a 2-2 ordering along the c axis. This arrangement creates two different M2 sites.