Size effects in PbTiO 3 nanocrystals: Effect of particle size on spontaneous polarization and strains

E. K. Akdogan, C. J. Rawn, W. D. Porter, E. A. Payzant, A. Safari

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Abstract

The spontaneous polarization (Ps) and spontaneous strains (xi) in mechanically unclamped and surface charge compensated PbTiO3 nanocrystals were determined as a function of particle size in the range <150 nm by differential scanning calorimetry and x-ray powder diffraction, respectively. Significant deviations from bulk order parameters (P, xi) have been observed as the particle size decreased below ~100 nm. The critical size (rc) below which the ferroelectric tetragonal phase transforms to the paraelectric cubic phase was determined as ~15 nm. The depression in transition temperature with particle size is 14 °C at 28 nm. No change in the order of m3m→4mm ferrodistortive phase transition is observed. A simple analysis showed that Δ Htr (kB T) ~ 103 at 25 °C for r=16 nm, indicating that the stabilization of the cubic phase at rc cannot be linked to an instability in dipolar ordering due to thermal agitations. Comparison of the spontaneous volumetric strains with the strain induced by surface stress indicated that the effect of surface stress on ferroelectric phase stability was negligible. Anomalies in electrostrictive properties were determined for r→ rc. The observed size dependence of PS is attributed to the reduced extent of long-range dipole-dipole interactions that arise due to the changes in bonding characteristics of ions with decreasing particle size in the perovskite lattice, in conformity with a recent study by Tsunekawa [Phys. Rev. Lett. 85 (16), 4340 (2000)].

Original languageEnglish
Article number084305
JournalJournal of Applied Physics
Volume97
Issue number8
DOIs
StatePublished - Apr 27 2005

Funding

The authors from Rutgers University are thankful for the financial support provided by the Malcolm McLaren Center for Ceramic Research at Rutgers University and the National Science Foundation. Research sponsored by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Transportation Technologies, as part of the High Temperature Materials Laboratory User Program, Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. The assistance of J. Bai in the x-ray synchrotron work that was carried out in the National Synchrotron Light Source (NSLS) beamline X-14A at the Brookhaven National Laboratory (BNL) is greatly appreciated.

FundersFunder number
Office of Transportation Technologies
National Science Foundation
U.S. Department of EnergyDE-AC05-00OR22725
Office of Energy Efficiency and Renewable Energy
Oak Ridge National Laboratory
Rutgers, The State University of New Jersey

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