Effects Of Periodic Undulation On Elastic Waves Propagating In PMN-0.29PT Single Crystal Layered Structures

The piezoelectric constant,the electromechanical coupling coefficient and the strain of relaxed ferroelectric Lead Magnesium Niobate-Lead Titanate single crystal(PMN-PT)far surpass the commonly used piezoelectric ceramics,which would be great promise candidates for the next generation of piezoelectric ultrasonic transducers,sensors,and actuators with high efficiency and high sensitivity.This makes this single crystal great potential for the applications in the fields of medical ultrasound imaging,underwater sonar detection,and various sonic and microwave devices.The performance of PMN-PT single crystal with elastic wave propagating it's the layered structure is an important foundation for realizing the electro-acoustic energy conversion,sensing and driving of piezoelectric devices.Therefore,knowledge of the behaviors of the elastic wave propagation is a key issue for the understanding and design of PMN-PT single crystal devices.However,the uneven boundary and rough surface of the single crystals and layered structures are inevitably during their growth and machined processes.The modeling and simulating of the uneven surface and interface and the understanding of the influence from a wave motion analysis can provide some foundations for the design and application of the piezoelectric device.In this dissertation,we focus on several types of elastic wave propagating in PMN-PT single crystal layered structures with corrugated boundary surfaces,the following results are drawnThe effect of periodic undulation on the propagation properties of several types of elastic waves in PMN-PT single crystal layered structures and bi-material plate is investigated.The PMN-PT single crystal is poled along [011]c direction so that the macroscopic symmetry is orthonormal mm2.The general solution of the problem is obtained.The weak cosine harmonics is employed to describe the periodic undulation of the surface and interface of the layered structure,and the dispersion relations of Love wave,Rayleigh wave and Lamb wave under the condition of surface electrically open circuit and shorted circuit are derived.The effects of various parameters including corrugation,undulatory,position and electrical boundary conditions on the dispersion properties of elastic wave are discussed.The results show that the corrugation amplitude parameters of the surface and interface play a major role in the propagation characteristics of the elastic wave.In the low frequency and small wavenumbers,the corrugation amplitude of upper surface can produce an obvious gain of phase velocity of elastic wave and has a positive correlation within a certain range.That is to say,the phase velocity increases with the corrugation amplitude parameter increasing.However,The corrugation amplitude of interface between the over layer and the substrate reduces the wave speed of the elastic wave due to the fact that the stiffness of the structural interface is weakened by the interfacial corrugation.Comparing with the amplitude parameters,the corrugation wavenumber and position parameter have less influence on the propagation characteristics of elastic wave,especially for the Love wave and Rayleigh wave.The influence of corrugation wavenumber and position parameter on phase velocity gradually disappears as the non-dimensional increasing.The obtained results can provide some theoretical foundations for the parameter configuration and optimization of piezoelectric traveling wave amplifiers,distributed feedback oscillators,phase shifters and delay lines,as well as for the structure design of surface and interface and regulation control of the acoustic and microwave devices.