Improvement of energy storage characteristics of (Ba0.7Ca0.3)TiO3 thick films by the increase of electric breakdown strength from nano-sized grains; [절연파괴특성 향상을 위한 나노미세구조 (Ba0.7Ca0.3)TiO3 후막 제조 및 에너지 저장 특성 평가]

초록

Lead free (Ba0.7Ca0.3) TiO3 thick films with nano-sized grains are prepared using an aerosol deposition (AD) method at room temperature. The crystallinity of the AD thick films is enhanced by a post annealing process. Contrary to the sharp phase transition of bulk ceramics that has been reported, AD films show broad phase transition behaviors due to the nanosized grains. The polarization-electric hysteresis loop of annealed AD film shows ferroelectric behaviors. With an increase in annealing temperature, the saturation polarization increases because of an increase in crystallinity. However, the remnant polarization and cohesive field are not affected by the annealing temperature. BCT AD thick films annealed at 700 °C/2h have an energy density of 1.84 J/cm3 and a charge-discharge efficiency of 69.9%, which is much higher than those of bulk ceramic with the same composition. The higher energy storage properties are likely due to the increase in the breakdown field from a large number of grain boundaries of nano-sized grains. © 2019, Materials Research Society of Korea.

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