Editors : S.B. Desu, R. Ramesh, T. Shiosaki, B.A. Tuttle
a1 Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185
We have characterized the pyrochlore-to-perovskite crystallization process in solution-derived Pb(Zr0.20Ti0.80)O3 thin films on (100) MgO single crystal substrates. It has been determined that the perovskite phase nucleated preferentially at the film/MgO interface out of a nanocrystalline (≈100Å grains) pyrochlore matrix. During the early stages of the pyrochlore-to-perovskite conversion process, perovskite growth proceeded nearly isotropically from the substrate to form hemispherically shaped grains. Deviations from isotropie growth were shown to result from a growth dependence based on the crystallographic orientation of a growing perovskite grain relative to the orientations of pyrochlore grains being transformed. The volume change that occurs during the pyrochlore-to-pervoskite transformation along with two-dimensional grain growth has been used to develop a mechanism for formation of porosity that commonly is concentrated in grain boundary regions.