By means of DTA,RTEM,X-ray and IR techniques,the phase separationmechanism and relations between the phase separation and crystallization in theAl(PO_3)_3-NaBF_4-AlF_3 glass system have been investigated.The experimental results of DTA and RTEM indicate that there are two T_gtemperatures on the DTA curves of the phase separated glass.The phase separationmechanism of the system belongs to nucleation and growth mechanism.The growthrule of the phase dispersed particles obyes the diffusion-controlled mechanism....