Polarization echoes in piezoelectric—ferroelastic powders

A theoretical description is given for nonlinear formation mechanisms and properties of the polarization echoes in piezoelectric-ferroelastic powders. A phenomenological model is elaborated for dynamics of dislocations and domain boundaries in mechanically vibrating piezoelectric particles resonantly excited by short duration pulses of rf electric field. The model includes both the reversible and irreversible motion of dislocations generated by Frank-Read sources and similar behavior for domain walls. The amplitude-dependent acoustic frequency change and amplitude-dependent damping obtained by use this model constitute two of the three nonlinear mechanisms responsible for the formation of the polarization echoes in piezoelectric powders with the signals naturally consisting of both the dynamic and the memory components. As a third type of the nonlinearities, the field-mode interaction, we take the nonlinear electrostriction. General expressions for two pulse echoes and three pulse memory echoes are derived by use together all the three types of nonlinear mechanisms. The numerical analysis of these expressions as a function of the pulse amplitudes, the pulse widths and the pulse separation shows qualitative agreement between the theory and the existing experiments in broad range of amplitudes and widths of the pulses.

Keywords:

• Piezoelectric-ferroelastic
• vibrations
• internal friction
• dislocations
• domain walls
• echoes
• powders
• memory