The crystallization behavior of $K_2O-SiO_2$ glasses with added $TiO_2$ and the effect of $TiO_2$ on internal nucleation at temperatures in the range of 875 to 1210℃ have been investigated by means of X-ray diffractometry, optical microscopy and scanning electron microscopy.
The crystalline phase of these glasses identified by X-ray diffractometry is cristobalite.
The scanning electron microscopy reveals a two-phase layer of dendritic crystals and interstitial melt which grow from the surface at a constant rate. The observed crystallization rates are consistent with a diffusion-controlled mechanism.
An equation relating viscosity and undercooling to growth rate is presented.
In dendritic crystallization, experimental relationship between secondary arm spacing and growth rate is obtained.
Dendrite coarsening during isothermal holding shows that the secondary arm spacing increases with heat-treatment time.