Ferroelectric transitions in small particles

ABSTRACT

In this article, the experiments on growth of small ferroelectric-salt particles from their aqueous solutions are analyzed with the help of the Landau-Ginzburg-Devonshire theory of phase transitions. Contrary to the most common trend, the paraelectric-ferroelectric transition temperature is found to increase with the decreasing size of the particle. This is attributed to the electrocapillarity effect that is, decrease of the surface energy between the particle and its solution with the emergence of the charge on it. The theoretical analysis found that the electrocapillarity effect here is due to the depolarization field of the spontaneously polarized ferroelectric phase. Application of the theory to the experiments on quasi-static cooling and drying of aqueous solutions of ferroelectric salts resulted in quantitative explanation of the experiments. Suggestions are made regarding novel experiments, which may clarify properties of small ferroelectric-salt particles and help design new methods of their fabrication.

Acknowledgment

One of the authors (AU) would like to thank A. Levanyuk for helpful discussions.

Funding

The authors acknowledge financial assistance provided by the award 70NANB14H012 from NIST U.S. Department of Commerce as part of the Center of Hierarchical Materials Design at Northwestern University.