Acoustoelectric Nonlinearity in Periodically Poled Lithium Tantalite

Abstract

Some new nonclassical nonlinear acoustic phenomena in ferroelectric lithium niobate are reported last years. They are a) thermal hysteresis of nonlinear ultrasonic attenuation, b) acoustic memory, which is a strong non‐exponential echo train that may not be explained by a nonparallelism of a sample, c) acousto‐domain interaction that was detected by X‐Ray technique and consists of a reorientation of the crystal lattice substructures under nonlinear action of ultrasound, d) new class of crystal sonoluminescence, which is generated at ferroelectric surface by the acoustic vibrations. In these phenomena, the involvement of the ferroelectric domain boundaries is experimentally identified by acoustically induced evolution of the X‐ray diffraction patterns, chemical etching of the crystal surfaces, temperature characteristics of the effects observed, and by the changes in acousto‐electric properties of a sample.In this work, we report our experiments with lithium tantalite vibrators of two different types: a) two‐dimensional multi domain array of the inversely poled ferroelectric domains in a y‐rotated cut, and b) regular vibrator made of a single crystal. We measure the amplitude characteristics of rf‐admittance (Y) of the samples in Megahertz frequency (f) range at room temperature. A strong nonlinearity is detected. The distortions in the Y(f) dependencies occur under increasing of ultrasonic excitation. These distortions are much stronger in multi domain sample with a number of so called domain walls. The experimental results allow making a conclusion on nonlinear vibrations of the domain walls in an acoustic field, and to discuss their contribution to nonlinear nonclassical phenomena.