Solidification behavior and microstructure of (Ba,Sr) TiO3 ceramics prepared by aerodynamic levitation
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Semiconducting (Ba,Sr)TiO3 ceramics were solidified using an aerodynamic levitator and the solidification behaviors duringrecalescence and microstructure of the levitated (Ba,Sr)TiO3 ceramic were investigated. A spheroid (Ba,Sr)TiO3 wassynthesized from a homogeneous melt using an aerodynamic levitator. The recalescence was observed, indicating that theundercooled melt solidified into a polycrystalline (Ba,Sr)TiO3 phase. The levitated sample exhibited a radial dendrite structureoriginating from a surface nucleation point. Secondary dendrites on primary dendrites were formed due to temperaturevariations at the solid-liquid interface. The as-levitated sample was oxygen-deficient compared to the sintered sample. The aslevitated(Ba,Sr)TiO3 sample had a cubic structure, and the positive temperature coefficient of resistivity (PTCR)characteristics were not observed. To analyze the transformation kinetics during recalescence, the growth velocity of the solidphase was estimated from the snap shot images of the molten droplet during recalescence.
Abstract
Semiconducting (Ba,Sr)TiO3 ceramics were solidified using an aerodynamic levitator and the solidification behaviors duringrecalescence and microstructure of the levitated (Ba,Sr)TiO3 ceramic were investigated. A spheroid (Ba,Sr)TiO3 wassynthesized from a homogeneous melt using an aerodynamic levitator. The recalescence was observed, indicating that theundercooled melt solidified into a polycrystalline (Ba,Sr)TiO3 phase. The levitated sample exhibited a radial dendrite structureoriginating from a surface nucleation point. Secondary dendrites on primary dendrites were formed due to temperaturevariations at the solid-liquid interface. The as-levitated sample was oxygen-deficient compared to the sintered sample. The aslevitated(Ba,Sr)TiO3 sample had a cubic structure, and the positive temperature coefficient of resistivity (PTCR)characteristics were not observed. To analyze the transformation kinetics during recalescence, the growth velocity of the solidphase was estimated from the snap shot images of the molten droplet during recalescence.
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