abstract
A kinetic study of the growth of BaTiO3 under hydrothermal conditions using layered titanate nanotubes as precursors has been performed at 110 and 200 degrees C. At the early stages of crystallization, irrespective of temperature, pseudocubic BaTiO3 nucleates on the surfaces of the nanotubes. Growth subsequently proceeds by a phase-boundary mechanism with exponent m approximate to 1. During this first regime, "wild type" dendritic particles form with a rough surface and a microstructure which contains planar defects. As the reaction proceeds beyond 70% completion, the nanotubes fully dissolve, and nucleation and growth of tetragonal rather than pseudocubic BaTiO3 take place. During this second regime, the morphology of the BaTiO3 particles remains predominantly dendritic with "seaweed" morphology and a smooth surface, but smaller spherical precipitates and particles with a small number of dendritic arms are also observed. For this stage in the hydrothermal process, the exponent, m approximate to 0.2, does not correspond to any known kinetic mechanisms.
keywords
BARIUM-TITANATE; NANOCRYSTALLINE BATIO3; PHASE-CHANGE; PARTICLES; NANOWIRES; SIZE; POWDERS; NANOSTRUCTURES; MECHANISMS; CERAMICS
subject category
Chemistry; Crystallography; Materials Science
authors
Maxim, F; Vilarinho, PM; Ferreira, P; Reaney, IM; Levin, I
our authors
Paula Celeste da Silva Ferreira
Coordinating Researcher
Paula Maria Lousada Silveirinha Vilarinho
Vice Directoracknowledgements
The authors acknowledge the Portuguese Foundation for Science and Technology (FCT), FEDER, the European Network of Excellence FAME, under the Contract FP6-500159-1 and COST 539, Electroceramics from Nanopowders Produced by Innovative Methods (ELENA). Florentina Maxim is thankful to FCT for the fellowship SFRH/BD/23375/2005.