ESTIMATION OF PHASE-SEPARATION RATES OF BAO-B2O3 MELTS UNDER COOLING

The liquid-liquid phase separation rate was estimated experimentally i n the BaO-B2O3 system. Phase separation of BaO-B2O3 melts was observed continuously with a video camera as the melts were cooled from the ho mogenisation temperature at a rate of 2.5 degrees C/min. Droplets were precipitated and grew up to several micrometers in diameter after a f ew minutes. The apparent nucleation rate and apparent growth rate unde r cooling were calculated from the video pictures recorded. The diamet ers of the droplets increased quadratically,vith time in contrast to t hat the number of nuclei increased linearly with time The apparent nuc leation rate and apparent growth rate of the melt containing 10 wt% Ba O were calculated to be 90 mm(-2)s(-1) and 0.9 mu ms(-1/2), respective ly.