Fedoryako A. Relaxation processes and parametrical effects in pseudo-intrinsic ferroelectrics

Relaxation processes in thin films of pseudo-intrinsic ferroelectrics with different types of polymorphism have been studied. The obtained data on relaxation times allowed separation of the contributions to electromechanical conversion coming from piezoelectric and two types of flexoelectrics effects. The results of studies of piezoelectric properties have shown that the Curie principle for intrinsic ferroelectrics can be applicable for prediction of piezoelectric properties in pseudo-intrinsic ferroelectrics. It has been experimentally proven that the soft mode enhances the electromechanical transformation efficiency in SmC* phase near SmA* SmC* phase transition. The nonlinearity of electromechanical coupling was found to emerge as a result of the flexoelectric effect. The piezoelectric effect is linear. Frequency dependences of piezoelectric and flexoelectric coefficients have been measured, showing essentially non-linear character. In the spectrum of director vibrations, the presence of texture resonances of FLC piezoelectric domains has been found. Dependences of amplitude, frequency and quality factor of the texture resonance on temperature and intensity of electric field were studied. It has been shown that the amplitude of resonance vibrations reaches its maximum at the phase transition point SmA* - SmC*. Studies of open resonant systems were carried out, with FLC used as active medium. Parameterization of the resonant system occurred when FLC samples with chevron structure were used.