Relaxation, thermal, and interphase effects in polymer–ferroelectric-piezoelectric ceramic composites of different structures

The relaxation and thermal processes and interphase phenomena in composites based on ferroelectrics and a polymer matrix are studied. It is shown that the charge stabilized at the interface of the composite during its electrothermopolarization is mainly determined by the structure of the polymer matrix and the piezoelectric phase. The results obtained make it possible to reveal the main factors affecting the piezoelectric properties of the heterogeneous polymer–ferroelectric ceramic system. Polyolefins and fluorine-containing polar polymers are used as the organic phase, and ferroelectric ceramics of rhombohedral, tetragonal, and mixed structures serve as the inorganic phase. The relaxation processes and interphase phenomena are studied using a differential scanning calorimeter, and the charge state is analyzed by recording the thermally stimulated depolarization current. The charge-state stability is determined by the electret potential difference of the composites. The molecular relaxation is analyzed by the dielectric method. It is established that the composites in which the interphase interaction is more pronounced are characterized by high piezoelectric properties.