Free vibration of periodically poled ferroelectric plate

Abstract

A multidomain two-dimensional periodically poled ferroelectric plate vibrator is reported for the first time. The theoretical calculations, computer simulations by the Finite Element Method and experimental data from the lithium tantalite samples reveal a domain acousto-electric resonance. A polarization inversion in a y-rotated cut of a ferroelectric chip is firstly done. The acousto-electric characteristics of the vibrator are calculated and measured. Introduction. Multidomain ferroelectrics are the subjects of the rigorous fundamental physical investigations and possible applications during last decades since the first publications on fabrication of the periodic inversely poled structures [1-5]. Main areas of research are the fabrication of inversely poled micro-domains in bulk ferroelectric crystals, which are sometime referred to as one dimensional acoustic super-lattice, and their applications for ultrasonic transducers [6-12]. Different oxygen-octahedral ferroelectric crystals (LiNbO 3 , LiTaO 3 , KTiOPO 4 , and BaTiO 3 ) with the periodic domain structures have been reported [1, 3, 4, 9, 12, 13] in a one-dimensional bulk media. Scanning Electron Microscopy technique was employed to show a significant interaction of the surface acoustic waves propagating in a periodically poled lithium niobate [14], which results in some nonlinear effects [15]. The domain walls and associated complexes of crystal lattice defects are reported [16] to be responsible for a new type of nonlinear ultrasonic attenuation in lithium niobate. Last years a fabrication of the ferroelectric domains at the nanoscale is of great interest [17] view the potential applications in information storage devices and ferroelectric memory cells. The optical properties and generation of optical harmonics in periodic ferroelectric structures is another important application. At this point we want to mention a new type of polariton [18] discovered in a piezoelectric superlattice [1, 19].In point of fact, we can not refer to any publication on acoustoelectric properties of multidomain ferroelectric structures in two-dimensional ferroelectric resonators.

Multidomain ultrasonic transducers

“…In other words, if a total length of MDUT is L n = nd, a main resonance is still at the frequency f d corresponding to the length of only two domains ͑2d͒, that is, f d = v / 2d, where v is the ultrasound phase velocity in the multidomain structure. This result does not differ from the previous calculations for free vibrations of two-dimensional structures 16,17 and bulk multidomain crystals including acoustic superlattices 8 and recently published phononpolariton systems. 21 We can estimate the sums S n near the domain resonance by assuming low internal losses inside crystal.…”

“…In a plate-type acoustic waveguide, one can excite Lamb waves with longitudinal displacements u x and transverse displacements normal to surface u y ; and shear normal waves with the displacements u z along the z axis. 20 While the plate waves in a periodically poled ferroelectric plate have not yet been considered, our previous experiments with such multidomain samples of lithium tantalite 16,17 revealed analogous acoustic modes. For a longitudinal wave ultrasonic transducer, a zero symmetrical mode S 0 with u x 0 that propagates along x axis can be used.…”

“…Details of poling process are given in publications. 16,17 Two identical MDUTs were successfully produced. A microphotograph of the multidomain pattern of one of the fabricated devices, taken through polarizing microscope, is shown in the inset of Fig.…”

“…15 Recently, free vibrations of two-dimensional periodically poled ferroelectric wafers have been investigated and reported. 16,17 Among closely related works, we mention Refs. 18 and 19 in which, the finite element method is used to model polarization of ferroelectric ceramics and the piezoelectric effect in nanostructured ferroelectric films.…”

Split-mode ultrasonic transducer

“…Examples of recent developments include, but are not limited to, the rigorous research on High Intensity Focus Ultrasound 1,2 and its clinical aspects 3 including ultrasound applications for drug delivery, 4 medical ultrasonic transducers for high frequency operation, 5 and others. In this respect, research on periodically poled ultrasonic transducers is connected to ceramic materials with inversely poled ferroelectric domains, 6,7 their efficiency of acoustoelectric transduction in bulk, [8][9][10] and two-dimensional [11][12][13] acoustic superlattices. Other types of promising vibrators are multi-layer transducers, 5,14 which were invented more than 2 decades back.…”