Evolution of poled state in P(VDF-TrFE)/(Pb,Ba)(Zr,Ti)O3 composites probed by temperature dependent Piezoresponse and Kelvin Probe Force Microscopy

V. V. Shvartsman,D. C. Lupascu,D. A. Kiselev,A. V. Solnyshkin,M. V. Silibin

doi:10.1038/s41598-017-18838-1

Abstract

Polarized states of polymer/inorganic inclusion P(VDF-TrFE)-(Pb,Ba)(Zr,Ti)O3 composites are studied at the nanoscale using both piezoresponse force microscopy (PFM) and Kelvin probe force microscopy (KPFM). It has been shown that inorganic inclusions can be visualized using KPFM due to a discontinuity of the surface potential and polarization at the interface between the inclusions and the polymer matrix. The temperature evolution of the PFM and KPFM signal profiles is investigated. Softening of the polymer matrix on approaching the Curie temperature limits application of the contact PFM method. However non-contact KPFM can be used to probe evolution of the polarization at the phase transition. Mechanisms of the KPFM contrast formation are discussed.

Highlights

The most attractive ferroelectric polymer materials are copolymers of vinylidene fluoride and trifluoroethylene, P(VDF-TrFE)
To investigate the evolution of the KFPM contrast in more details we studied the temperature dependences of several Kelvin probe force microscopy (KPFM) signal profiles taken in various regions
We observed a sharp maximum of the 2nd harmonic piezoresponse force microscopy (PFM) signal close to the Curie temperature of the polymer matrix and its temperature dependence is qualitatively similar to the temperature dependence of the high-frequency dielectric permittivity for this compound[27]

Summary

Introduction

The most attractive ferroelectric polymer materials are copolymers of vinylidene fluoride and trifluoroethylene, P(VDF-TrFE). Contrary to the pure polyvinylidene fluoride, PVDF, these materials have a high degree of crystallinity, i.e. ratio between ordered and randomly arranged molecules in the polymer. They show ferroelectricity already in the as-grown state, which causes their good piezoelectric and pyroelectric properties[9]. Local heterogeneities of functional properties, which are characteristic for composite materials, can significantly affect the macroscopic performance Probing of such heterogeneities is highly demanded. Using piezoresponse force microscopy (PFM), local polarization reversal was studied in BaTiO3/ PVDF composite nanofibers[20] and (Na,K)NbO3 nanoparticle-embedded P(VDF-TrFE) nanofiber composites[21]. Temperature evolution of artificially created domains was investigated using both piezoresponse force microscopy (PFM) and Kelvin probe force microscopy (KPFM)

Methods

Results

Discussion

Conclusion