Nanotexture influence of BaTiO3 particles on piezoelectric behaviour of PA 11/BaTiO3 nanocomposites

摘要

The piezoelectric activity of a hybrid ferroelectric nanocomposite, i.e. polyamide 11/barium titanate (BT),udhas been investigated for different loadings of BT particles. The BT volume fraction (/) was ranging fromud0.024 to 0.4 with a particle size of 50, 100, 300 and 700 nm. The influence of polarization mode on theudpiezoelectric behaviour has been studied. The magnitude of the poling field used in this study is in theudsame order of magnitude of the one used for bulk BT i.e. significantly lower than for piezoelectric polymers.udThe optimum piezoelectric coefficient is reached when the amorphous phase of the polymericudmatrix is in the liquid state i.e. for a polarization temperature higher than the glass transition and for timeudconstant allowing macromolecular mobility. The composite piezoelectric activity decreases for particlesudsize lower than 300 nm due to the loss of the tetragonal phase. The nanotexture of these particles hasudbeen investigated by transmission electron microscopy (TEM) and high-resolution TEM. A core shelludstructure has been observed. An increase of the longitudinal piezoelectric strain coefficient d33 withudthe raising of BT volume fraction was shown. Contrary to inorganic piezoelectric ceramics, the dielectricudpermittivity of hybrid composites remains moderate; therefore it allows the piezoelectric voltage coefficientudof composites to be higher than ceramics.