Evolutions of rod diameter, molten zone and temperature gradient of oxide eutectic ceramics during laser floating zone melting

Laser floating zone melting (LFZM) is an important directional solidification (DS) technique in oxide ceramic fabrication owing to its very high temperature gradient and rapid cooling rate. In this work, variations and evolutions of rod diameter, molten zone, and temperature gradient are explored in fabrication of Al₂O₃-based eutectic ceramics. At low solidification rate of 4 μm/s, periodical oscillations with almost the same period (~275 s) are produced in melting zone shape/size, as-grown rod diameter, temperature distribution, and temperature gradient. The temperature gradient fluctuates between 3.6 × 10³ K/cm and 6.9 × 10³ K/cm with an average value of about 5.3 × 10³ K/cm. As increasing the solidification rate, the temperature gradient decreases and the periodical oscillation weakens. Based on the evolutions of the temperature field, interface location and molten zone shape, the formation mechanism of periodical oscillation during LFZM processing is evaluated.