Unusual Phase Transformations in Ceramics and Related Materials Under the Influence of an Electric Field
Technical Report,18 Aug 2014,17 May 2015
University of Colorado - Boulder Boulder United States
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We have conducted in-situ X-ray diffraction experiments at the Advanced Photon Source at the Argonne National Laboratory to explore the occurrence of unusual phase transformation or changes in crystal structure that are induced by electrical fields. Two specific results have been obtained. In one case the 1 1 0 and the 1 1 1 peaks in titanium oxide strengthen, while the 2 1 1 peak weakens, under the electric field at elevated temperature. The changes in the peak intensities are immediate, but they fluctuate with time even though the electric field remains constant. These fluctuations are ascribed to a difference in the interaction of charged defects, which are induced by the electric field, with different planes in rutile depending on the intrinsic charged state of the planes. In a second system the reaction between alumina and titania is shown to be remarkably enhanced by the electric field. Furthermore, aluminum-titanate is shown to form below the temperature given by the phase diagram, in support of the concept that electrical fields can produce phases that are far from equilibrium.
- Electricity and Magnetism