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CAREER: The Evolution of Polar Nanoregions and Its Coupling with Cation-Ordered Domains in Pb(B'B'')O 3 Relaxor Ferroelectrics Xiaoli Tan (Iowa State University), DMR 0346819.

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  1. CAREER: The Evolution of Polar Nanoregions and Its Coupling with Cation-Ordered Domains in Pb(B'B'')O3 Relaxor FerroelectricsXiaoli Tan (Iowa State University),DMR 0346819 Ferroelectric ceramics change their dimensions significantly when subjected to electric fields. Therefore, they have been used widely in energy storage and conversion devices. The properties of these ceramics are largely dependent on their microstructures. Pb(Mg1/3Nb2/3)O3-based ceramics are such materials with unique microstructures: (1) the cation ordered domains where Mg2+ and Nb5+ occupy different crystal lattice sites, and (2) the polar domains where Pb2+ displacements are aligned parallel. One major achievement in the past year of this project is the direct visualization of the interactions between the cation ordered domains and the polar domains, as shown in Fig. 1. The detailed results are published in the Journal of Applied Physics (Vol. 102, article 084101, 2007). The other major finding is the development of large cation ordered domains in Zr-doped Pb(Mg1/3Nb2/3)O3-ceramics (to be published in the Journal of the American Ceramic Society). This result is contradictory to a previous study by other researchers (Ref. 1). The research supported by this project is important because it will lead to materials with better energy conversion efficiency. Ref. 1. M.A. Akbas and P.K. Davies, J. Am. Ceram. Soc., 83, 119-23 (2000). (a) (b) Fig. 1. Transmission electron microscopy micrographs recorded at the same position in a ferroelectric ceramic. (a) The polar domains, and (b) the cation ordered domains.

  2. CAREER: The Evolution of Polar Nanoregions and Its Coupling with Cation-Ordered Domains in Pb(B'B'')O3 Relaxor FerroelectricsXiaoli Tan (Iowa State University), DMR 0346819 • The primary educational activity for this CAREER grant was to recruit undergraduate students to the PI’s research lab from underrepresented groups as summer interns. Roshnika Fernando, a female sophomore undergraduate student majored in Physics at the Lake Forest College, was selected through the Program for Women in Science and Engineering (PWSE) and worked on this project from June through July in 2007. Laura Choate, a female sophomore at Arizona State University majored in Optical Engineering, is the PWSE summer intern for 2008 and is currently working in the PI’s lab. The interns are trained with ceramic powder processing, dielectric/ferroelectric characterization, and electron microscopy. At the end of the internship, they prepare a poster based on their work and participate the poster competition with all other summer interns in the PWSE program. Through the summer internship in the PI’s lab, Roshnika Fernando became strongly interested in Materials Science research and applied more materials-related internships for the summer 2008. With the support of this project, the PI also recruited Joshua Frederick as an undergraduate research assistant for the summer of 2008. Joshua is an American Indian and graduated from the Iowa State University (ISU) in May 2008. • In the past year, the PI hired Daniel White, a senior undergraduate student at ISU. Under the PI’s direct supervision, he successfully completed the experimental work on a unique piezoelectric solid solution system. A manuscript has been derived from the data he generated and was submitted to the Journal of Materials Science for publication. The research training in the PI’s lab has inspired Daniel White for further graduate school study on electroceramics. With the PI’s encouragement and recommendation, Daniel is admitted as a graduate student by the Department of Materials Science and Engineering at the Rutgers University. • Through the support from this project, the PI has developed international collaborations with Prof. Zuo-Guang Ye at Simon Fraser University in Canada. The joint research has lead to one publication in the Journal of Physics: Condensed Matter. • The significant contribution to the field made by the PI through this project has been recognized by his peers. The PI has been invited to write a chapter for a technical textbook. He has also been the invited speaker at three international conferences.

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