Monitoring polarization and dielectric relaxation behaviors of BaTiO3/PC composite films via transmittance measurement

BaTiO 3 /polycarbonate (BT/PC) composite films with different concentration of BaTiO 3 ferroelectric nanocrystals are prepared by a spin coating method. The polarization and dielectric relaxation behaviors of BT/PC composite films are characterized by the introduction of orientational order parameter ( ϕ ) through in-situ transmission spectrum measurement. It's found that 15%BT/PC composite film has the largest orientation change with the ϕ value of 10.5% and slow dielectric relaxation, almost 10% decay of ϕ after 24 h. The optical band-gap of 15%BT/PC composite film decreases after poling indicates that the orientation of BaTiO 3 ferroelectric nanocrystals aligns due to the effect of polarization, from 3.8 eV to 3.67 eV. From the XRD results, we consider that the preferential alignment orientation of BaTiO 3 ferroelectric nanocrystals after poling is [001]. This suggests that in-situ transmittance measurement is a simple and effective way to evaluate the polarization and dielectric relaxation behaviors of ferroelectric nanocrystals/polymer systems.