SUPERCOOLING, INDUCTION TIMES AND NUCLEATION IN FLUX GROWTH: WO3 AS A MODEL SOLUTE

WOq was chosen as a model solute in this investigation of nu~leatlon by differential thermal analysis (DTA) and flux growth experiments. The compositions studied were: (I) 100 WOq-22 Na20 and (2) 100 W~3-44 NaF The first composition supercooled 13 °C, the second 70°C when cooled at 20o per minute. Induction time experiments for WO~-NaF are interpreted as indicating that clusters of WO~ retain their identity even after heating to 480 oC above the llqui~us, quickly reaching an equilibrium size at each soak temperature. Below the liquidus they increase in size but cannot form a stable nucleus until the critical supercooling of 35 °C is exceeded.