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CAREER: Fundamental Structure-Dielectric Property Relationships of Fluorite Related compounds Juan C. Nino, University of Florida, DMR 0449710 A2B2O7 Pyrochlore Structure Bi-based pyrochlores are among the most studied compounds in the family of fluorite-related structures due to their interesting dielectric properties. They A undergo a dielectric relaxation [time lag between electric field and polarization] that is temperature and frequency dependent. Given that BO6 bismuth is the dominant element on the A site of Bi-based pyrochlores, until recently, it was speculated that the observed relaxor dielectric behavior was O associated to the presence of Bi (with its lone electron pair). Dielectric relaxation in However, in collaboration with Ca1.469Ti1.469Nb1.037O7 pyrochlore NIST, CNRS, and CSIRO, we XRD profile confirming have now shown that a pyrochlore phase 110 displacive cubic pyrochlore not 0.14 containing bismuth, namely 100 0.12 Ca1.469Ti1.469Nb1.037O7, also (222) Intensity (Abitrary Units) Dielectric Constant 0.10 displays dielectric relaxation. Dielectric Loss 90 0.08 Ca1.469Ti1.469Nb1.037O7 Increasing the frequency This combined crystallographic 0.06 80 and electrical characterization 0.04 result provides an important 70 0.02 new insight into our 0.00 understanding of the nature of (111) (622) (400) (444) 60 -200 -150 -100 -50 0 50 100 150 200 250 the dielectric relaxation Temperature ( C) o behavior of pyrochlores. 20 30 40 50 60 70 2 (degrees) CAREER: Fundamental Structure-Dielectric Property Relationships of Fluorite Related compounds Juan C. Nino, University of Florida, DMR 0449710 Education and Outreach As part of the educational and outreach component of this program, the PI organized and delivered the first in the series of International Workshops on Electroceramics across the Bolivarian countries in South America. This first workshop took place in the Universidad del Valle, Cali, COLOMBIA, from August 8-10, 2007. The local host was Prof. Pedro Prieto, director of the Excellence Center in Novel Materials (CENM). The workshop was attended by 68 participants including faculty, undergraduate and graduate students from across Colombia.. Topics covered included dielectrics, ferroelectrics, fuel cells, and thermoelectrics and were presented by the PI Nino, P. Prieto, and faculty from other Colombian universities through a series of technical talks and laboratory tours. Besides the technical sessions, there was very fruitful general discussion on opportunities for Colombian faculty and students towards scientific collaboration and exchange with University of Florida and the US in general.
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