Ferroelectric nanocomposite and polar hybrid sol-gel materials for efficient, high energy density capacitors
Kim, Yun Sang
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The development of efficient, high-performance materials for electrical energy storage and conversion applications has become a must to meet an ever-increasing need for electrical energy. Among devices developed for this purpose, capacitors have been used for pulsed power applications that require large power density with millisecond-scale charge and discharge. However, conventional polymeric films, which possess high breakdown strength, are limited due to low permittivity and hence compromise the energy storage capability of capacitors. In order to develop high energy density dielectric materials for pulsed power applications, two hurdles must be overcome: 1) the appropriate selection of materials that possess not only large permittivity but also high breakdown strength, 2) the optimization of material processing to improve morphology of dielectric films to minimize loss during energy extraction process. This thesis will present the development of novel dielectric material, with emphasis on the optimization of material and thin film processing toward improved morphology as ways to achieve high energy density at the material level. After first two chapters of introduction and experimental details, Chapter 3 will demonstrate the improvement of nanocomposite morphology via processing optimization and study its effect on the energy storage characteristics of nanocomposites thereof. Chapter 4 will investigate dielectric sol-gel materials containing dipolar cyano side groups, which are relatively a new class of material for pulsed power applications. Finally, Chapter 5 will discuss the effect of tunneling barrier layer on sol-gel films to mitigate charge carrier injection and associated conduction and breakdown phenomena, which would be significantly detrimental to the energy storage performance of dielectric sol-gel films.