Core Shell/Barrier Layer Structured Ceramics: Physical Mechanisms of Enhancements of the Desirable Dielectric Properties

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NON-TECHNICAL SUMMARY: Capacitors are devices which store electrical charge, and as such are essential components of almost all electrical machinery and modern electronic devices. The continuing need for increased storage capacity of such devices, as well as for functional stability and miniaturization, make capacitive materials a competitive and promising area for expanded research and development, with exceptionally high potential for practical innovations and discoveries of a fundamental nature. The electronic components industry depends heavily on superior capacitor performance, and such components immediately impact the global market, paving the way for higher efficiency devices and often to new product innovations. The aim of the proposed investigation, therefore, is to explore the structural limitations of optimized capacitors based on barium titanate ceramics, and to use modern physical concepts, including nanotechnology, to develop superior capacitor systems and new devices based on these concepts. The high cost of fossil fuels of necessity focuses attention on the development of alternate energy conversion and storage strategies. An ambitious goal of the proposed research is to develop a capacitor system (a supercapacitor) that will convert solar energy and store it as electrical energy. Such solar rechargeable supercapacitors can revolutionize energy and transportation technologies and be widely applied to various sensor and storage devices. The proposed research is multidisciplinary and will involve participation by students with outreach to high school students and their teachers. The experience gained in these exercises will significantly advance their science background education and awareness of engineering materials. TECHNICAL SUMMARY: Barium Titanate (BaTiO3) continues to be the preferred dielectric material for capacitor use, because of its inherently high dielectric constant, and almost limitless potential for chemical modification to enhance dielectric and storage properties. Superior BaTiO3 capacitative systems have originated from core-shell structuring of the grains, with chemical gradients induced by doping, leading to stress-strain micro-domains and high polarization. The proposed research will explore these issues in depth, experimentally and theoretically, with the aim of minimization of percolative recombination loss of the stored charge, yielding high breakdown voltages and high dielectric constants. Effects of grain dimensions down to the nanoscale will be analyzed in detail to identify and quantify gradient features in the prepared microstructures, and to develop analytical relationships linking these structures to exhibited properties. Based on these associations, the proposed study will also focus on fabrication methodologies for nanostructured supercapicitors. A futuristic goal will be to develop devices that can harvest sunlight and store it as electrical potential energy in the supercapacitor. A possible strategy might involve integration of a dye-sensitized solid-state solar cell with the nanostructured supercapacitor, requiring exploration of loss issues resulting from recombination of the separated charges. The proposed work is multidisciplinary in scope, involving condensed-matter physics, electronics and materials science, instrumentation analysis and chemistry. This gives wide scope for the training of graduate students, as well as outreach to and involvement of undergraduate and high school students in hands-on experiments.