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.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.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 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

At present time, for excitation and reception of acoustic waves in cylindrical waveguides or rods, one uses a few types of transducers, but they are used only for excitation and reception of waves in nonpiezoelectric waveguides. The present paper firstly describes the circular transducer for excitation and reception of acoustic waves in piezoelectric cylinder. The principle of its operation is similar to interdigital transducer (IDT) for surface and plate acoustic waves. As waveguide, we used the cylinder of piezoceramics PZT­24U (Russian title) with a diameter of 6,5 mm and length of 15 mm. The calculation of the transducer parameters was based on piezoactive compressional wave C0 with frequency of ~625 kHz, for which the velocity is equal ~2000 m/s, and wavelength turns out to be 3,2 mm. The production of the circular transducer was performed by deposition of the aluminum strips through the mask on the lateral surface of the cylinder in vacuum. As mask, we used the system of rings of teflon with a width of 0,8 mm and thickness of 0,6 mm, which were placed on the cylinder with gaps of 0,8 мм. Then a sample was set in vacuum chamber on the special holder which allowed to turn it around own axis. The deposition of the aluminum was performed from tungsten basket by rotation of the cylinder on 70-90° before each act of deposition. Then, under the microscope, the teflon rings were cut and removed without slipping on the circular strips. The electrical conductance of strips was checked by standard ohmmeter. Then, by analogy with IDT for surface and plate acoustic waves, the aluminum rings were connected by turns with contact plates. The measurement of electrical impedance of circular transducer was carried out with the help of precision LCR meter 4285A (Agilent). For prevention of resonances on the length of cylinder the aggregate of chaotically located grooves with depth of half of wavelength were made on cylinder-s edges. The resonant peaks on the frequency dependencies of electrical impedance corresponding to the excitation of various acoustic modes were found. Under the assumption that these modes are excited by circular transducer and the wavelength is equal to its period, the values of the velocity were estimated. This allowed one to make the identification of the wave types by using the known theoretical data. It was found that theoretical and experimental values of velocity are different and maximum value of discrepancy is equal 15,7%. This discrepancy may be connected with accuracy of the measurement of resonant frequencies due to parasitic reflections from edges of cylinder as well as to absent of exact values of material constants of piezoceramics PZT­24U (Russian title). Also we made the delay line consisting of two aforementioned cylinders joined by epoxy with two circular transducers. By using the meter of S - parameters E5071С (Agilent) the frequency dependencies of the insertion loss and phase of this delay line was measured. The analysis has shown that the most attractive range is equal 960-1000 kHz, for which the insertion loss changes in limits of 4,8-9 dB. This work is financially supported by grant of President of RF for Scientific Schools- 4841.2014.9.

 

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