Surface layer clamping as origin for size-dependent downshift of Curie temperature in PbTiO3 nanoparticles

Size dependent Curie temperature in ferroelectric nanoparticles has been shown to originate from mechanical clamping of phase transition in particle core by a cubic surface layer. Based on a phenomenological model, the widely observed empirical relation between downshift of Curie point and particle size has been deduced by introducing an extra term of core-shell boundary energy into the free energy expression. Theoretical calculations of size dependent Curie temperature in PbTiO3 nanoparticles are in well agreement with the literature-reported experimental data. The positive boundary free energy of nano-sized PbTiO3 particles becomes increasingly large with size reduction, leading to a sharp drop of Curie temperature as compared to bulk single crystal. (c) 2013 Elsevier B.V. All rights reserved.