Optical properties of novel poled ferroelectric nanocrystals and polymer BaTiO₃/PC composite films

BaTiO3(BT) nanocrystals doped polycarbonate polymer composite thin films (BT/PC) with different BT concentrations were prepared by spin coating method. Ultra-fine BT (∼40-50 nm) nanocrystals with pure perovskite tetragonal phase were synthesized by hydrothermal method. The structure of BT nanocrystals and composite films were studied by means of XRD and TEM. The composite films were poled with a high electric field at a suitable temperature to yield a non-centrosymmetric arrangement and get better electro-optic properties. The Electro-optic (E-O) coefficients of composite films with various BT concentration were also evaluated. The average effective linear E-O coefficient and figure of merit of 20 wt% BT doped composite films were estimated to be 63.1 pm/V and 103.1 pm/V, respectively. The E-O properties of BT/PC composite films were further enhanced by increasing the concentration of the doped BT nanocrystals when the concentration of BT nanocrystals in composite films was low. The orientation degree of BT nanocrystals in PC polymer was detected by measuring the transparency spectra of unpoled and poled composite thin films.