Fabrication and Electro-optic Properties of Ferroelectric Nanocrystal/Polymer Composite Films

Abstract

BaTiO 3 (BTO), Pb(Zr 0.52 Ti 0.48 )O 3 (PZT), and Sr 1- x Ba x Nb 2 O 6 (SBN; x = 0.5, 0.4, and 0.25) nanocrystal-doped polycarbonate (PC) composite thin films were prepared by a spin-coating method. Ultrafine BTO and PZT nanocrystals of pure tetragonal perovskite phase were synthesized by a hydrothermal method, while the rodlike SBN nanocrystals of pure tetragonal tungsten−bronze structure were prepared by the Pechini method. To produce better electro-optic (EO) properties through creation of noncentrosymmetry in the samples, the composite films were poled under a high electric field at suitable temperatures. Their EO coefficients as well as transmittance spectra were measured. Both BTO/PC and PZT/PC composite films showed excellent EO properties with high EO coefficients and large figures of merit. However, SBN/PC composite films established relatively small EO coefficients due to the small transverse EO coefficients of SBN single crystals. On the basis of our results, we demonstrate that these ferroelectric nanocrystal/polymer composite films are good candidates for EO applications.