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