POLAR-ORIENTED CRYSTALLIZATION OF FRESNOITE (BA2TISI2O8) ON GLASS-SURFACE DUE TO ULTRASONIC TREATMENT WITH SUSPENSIONS

Improved polar (c-axis) oriented growth of fresnoite (Ba2TiSi2O8) was observed for surface crystallization of a glass 33.3BaO.16.7TiO(2).50SiO(2) (in mol%) due to ultrasonic surface treatment with an aqueous suspension of Ba2TiSi2O8, and an oriented film more than 50 mu m in thickness was prepared. The effect of ultrasonic treatment on the polar orientation depends on the suspending particles; of these, foreign particles of a phase other than the crystallizing Ba2TiSi2O8 give poorer efficiency than the Ba2TiSi2O8 particles. It is assumed that fresnoite has a tendency toward preferred polar growth on the glass, and seeding of a large number of fine particles through ultrasonic bombardment realizes the tendency. The polar-oriented growth kinetics of Ba2TiSi2O8 were also discussed.