Nucleation and growth behavior of Er 3+ doped oxyfluorophosphate glasses.

The nucleation and growth behavior of glasses with the composition (75 NaPO 3 -25 CaF 2 ) 100- x -(TiO 2 /ZnO/MgO) x , with x = 0 and x = 1.5 (in mol%) is investigated. The glasses possess similar activation energy for crystallization and Johnson-Mehl-Avrami exponent, with value 2 confirming bulk crystallization of crystals with needle like shape. The Ti and Mg glasses exhibit broader nucleation curve and higher T n max than the x = 0 and Zn glasses due to their stronger field strength. The crystal growth rates were determined and validated using SEM. Finally, we showed that the nucleation and growth of glasses can be controlled due to the large difference between onset of crystallization and maximum nucleation temperature which is crucial when preparing novel transparent glass-ceramics.