NSF East Asia and Pacific Summer Institute (EAPSI) for FY 2013 in Japan

Yeager Charles B, University Park PA

Investigators

Abstract

This action funds Charles Yeager of graduate Penn State University to conduct a research project in the Mathematical and Physical Sciences area during the summer of 2013 at Tokyo Institute of Technology. The project title is "Increasing Power from Thin Film Vibration Harvesters to Power Autonomous Sensor Networks." The host scientist is Professor Hiroshi Funakubo. Piezoelectric energy harvesting systems can convert ambient mechanical vibrations into a source for electric energy to power microelectromechanical sensors and there is a drive to increase the harvested power level to allow more sophisticated sensor systems, or enable the duty cycle for data transmission to be increased. The Fellow recently made an experimental characterization of piezoelectric lead zirconium titanate (PZT) thin films to be used in vibration energy harvesting systems and demonstrated that increasing the c-axis texture in the film allowed the energy generation figure of merit to increase. This work has raised questions as to the magnitude of the energy generation properties of PZT films with 100% c-axis texture. This project grows PZT films by metalorganic chemical vapor deposition at several compositions and with systematically changing c-axis texture to find how the single-domain energy generation factor changes as a function of composition, as well as reporting the highest possible property for this application. The c-axis texture is controlled by selecting substrates with appropriate thermal expansion coefficient and through growth temperature. These are primary factors to control thermal stress. It is predicted that a 100% c-axis PZT 30/70 film would have twice the figure of merit as the best reported PZT grown by sol-gel. Also, fundamental knowledge is gained by the direct measurement of how the transverse piezoelectric coefficient changes with c-axis texture for {001}PZT films. The c-axis texture is characterized by 4-circle X-ray diffraction and by infrared spectroscopy as well. The piezoelectric coefficient is characterized by the wafer flexure method. Broader impacts of an EAPSI fellowship include providing the Fellow a first-hand research experience outside the U.S.; an introduction to the science, science policy, and scientific infrastructure of the respective location; and an orientation to the society, culture and language.These activities meet the NSF goal to educate for international collaborations early in the career of its scientists, engineers, and educators, thus ensuring a globally aware U.S. scientific workforce. Furthermore, the experience and results of the research will be presented at the Fellow's home institution to groups of various backgrounds.