B.D. Zaitsev - Dr. Sc. (Phys.-Math.), Professor, Head of Laboratory of Physical Acoustics, Saratov branch of Kotel\'nikov IRE of RAS E-mail: zai-boris@yandex.ru A.M. Shikhabudinov - Ph. D. (Phys.-Math.), Research Scientist, Saratov branch of Kotel\'nikov IRE of RAS E-mail: alex-sheih@yandex.ru I.A. Borodina - Ph. D. (Phys.-Math.), Senior Research Scientist, Laboratory of Physical Acoustics, Saratov branch of Kotel\'nikov IRE of RAS E-mail: borodinaia@yandex.ru A.A. Teplykh - Ph. D. (Phys.-Math.), Senior Research Scientist, Laboratory of Physical Acoustics, Saratov branch of Kotel\'nikov IRE of RAS E-mail: teplykhaa@mail.ru I.E. Kuznetsova - Dr. Sc. (Phys.-Math.), Associate Professor, Leading Research Scientist, Laboratory of Electronic Processes in Semiconductor Devices, Kotel\'nikov IRE of RAS (Moscow) E-mail: kuziren@yandex.ru

It is well known that non-contact methods of excitation of acoustic waves can significantly widen the possibilities of nondestructive evaluations. These methods take on special significance when the mechanical contact of the transducer with object under study or use of contact liquids is impossible. This paper is devoted to a new method of excitation and reception of bulk acoustic wave in piezoelectric plate placed above the piezoelectric wave-guide of delay line operated on shear-horizontal acoustic wave of zero order (SH0). This wave-guide represented the piezoelectric of lithium niobate (LiNbO3) of Y cut with thickness of 200 µm. The lower side of the plate contained two inter-digital transducers (IDT) which excited and received SH0 wave propagating along crystallographic axis X. The distance between IDT was equal 27 mm. The choice of orientation and thickness of the plate was determined by need of significant value of electromechanical coefficient, which in this case was equal ~30%. The delay line was connected to the meter of S parameters E5071C (Agilent) and the frequency dependencies of insertion loss and phase were measured in the working range of frequency. It was equal 2.6-3.8 MHz. Then the plate of lithium niobate of 128Y X cut with shear dimensions of 14.4×12 mm and thickness of 530 µm was placed above the wave guide and the frequency dependencies of insertion loss of such composite delay line was measured. The plate was oriented in such a way that its axis X was normal to the wave vector of wave in delay line. The con-struction allowed to move the upper plate along the delay line with invariable width of the gap. It was found that the resonant peak corresponding to frequency value of 3.516 MHz appeared on the frequency dependence of insertion loss when the upper plate was placed above the radiating IDT. Then the thickness of upper plate decreased by mechanical lapping and the measurement were repeated. As a result we have obtained the frequency dependencies of insertion loss of composite delay line for the thicknesses of 530, 500, 475, and 450 µm. It was found that for each aforementioned dependency we watched resonant peak at that with decreasing the plate thickness the frequency of peak increased. Experimental results allowed to build the dependence of peak frequency on the plate thickness which turned out to be linear. Theoretical analysis has shown that pointed peak corresponds to excitation of bulk shear acoustic wave propagating along the normal to the sides of upper plate with velocity of ~3600 m/s and vector polarization being normal to the axis X. This analysis has also shown that this wave is excited by tangential component of electric field of IDT, which is oriented along the normal to axis X. The work was financially supported by the Program of the Support of Leading Scientific Schools (Grant SS-4841.2014.9) and Grant of Russian Foundation of Basic Research (№ 14-02-31352 mol-a).

 

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