CAREER: Fundamental Structure-Dielectric Property Relationships of Fluorite Related compounds

1. CAREER: Fundamental Structure-Dielectric Property Relationships of Fluorite Related compounds Juan C. Nino, University of Florida, DMR 0449710 The next generation of solid oxide fuel cells will require electrolyte materials with high ionic conductivities in the intermediate temperature (IT) range from 400 – 800°C. We have shown that ceria 15% singly doped with Nd3+ shows the highest grain ionic conductivity. Using pulse laser deposition, epitaxial single crystal thin films of doped ceria are being grown in order to measure the ionic conductivity across the film thickness. For the first time ever, dense phase pure Bi2Ti2O7 polycrystalline pellets were synthesized following a co-precipitation method. This maiden achievement has thus allowed for the thermophysical, crystallographic, and dielectric characterization of the Bi2Ti2O7 pyrochlore. A modification to the phase diagram of the Bi2O3-TiO2 system was proposed based on the results of the investigation. Using density functional theory (DFT) simulations it was proved that the most stable structure for Bi2Ti2O7 is a cubic structure with atomic displacements. Multiple local minima were stabilized and the energy profile between minima were identified (shown above). With energy barriers of ~ 0.15 eV, simulations suggest that Bi2Ti2O7 should have dielectric relaxation due to atomic hopping events. Juan C. Nino - NSF Highlights 2011 - DMR-0449710

2. CAREER: Fundamental Structure-Dielectric Property Relationships of Fluorite Related compounds Juan C. Nino, University of Florida, DMR 0449710 Education and Outreach During the last year, one of the graduate students, Roberto Esquivel, has submitted two papers for publication; one on SiC and one on Bi2Ti2O7. Two new graduates Christopher Turner and Calvin Davishave joined the project and are working on characterizing the dielectric response of Bi2Ti2O7 and Gd3TaO7. Alex Luis Ariascontinues his work on the characterization of single crystal growth of TGS-TGSeas part of his senior undergraduate research thesis. Junior Science, Engineering and Humanities Symposium Lab Tours • As part of the educational and outreach component of this project, we hosted a group from the Junior Science, Engineering and Humanities Symposium (JSEHS), This symposium promotes original research and experimentation in the sciences, engineering, and mathematics at the high school level. The visit gave the group of high school students an opportunity to see a state of the art materials research laboratory and participate in hands on experiments. We also set up various educational demos using novel electronic materials to further spark their interest in material science and engineering and STEM disciplines. Juan C. Nino - NSF Highlights 2011 - DMR-0449710