Crystal Growth Kinetics of 4K 2 O·CaO·10SiO 2 from Its Own Melt and Two Other Melts in the K 2 O‐CaO‐SiO 2 System

Crystal growth of 4K 2 O·CaO·10SiO 2 from its own melt occurred with a faceted interface, while crystal growth from a melt ∼4 wt% richer in silica than the crystal showed dendritic morphology and growth from a melt ∼5 wt% leaner in silica showed dendritic growth at undercoolings <10°C and faceted growth at undercoolings >30°C. The crystal growth velocities in all cases were independent of time and fit well the empirical relation In [ U/(T l ‐ T) 1.6 ] = A – Q/T , where U is velocity, A and Q are constants, and T l , is the liquidus temperature of the melt. The crystal growth data for the three melt compositions lie together in a narrow swath when plotted using the above equation. An explanation for this behavior is proposed which suggests that the phase boundary reaction aided by nucleation at surface sites provided by screw dislocations determines the growth kinetics even when the melt and crystal have different compositions.