I.A. Borodina

Investigation of acoustic waves in thin plates of lithium niobate and lithium tantalate

The general properties of fundamental antisymmetric A/sub 0/, symmetric S/sub 0/, and shear horizontal SH/sub 0/ acoustic waves propagating in thin piezoelectric plates have been theoretically investigated on samples of lithium niobate (LiNbO/sub 3/) and lithium tantalate (LiTaO/sub 3/). The results obtained will be useful for a proper development of various physical, chemical, and biological sensors and devices for signal processing based on plate acoustic waves.

Acoustic waves in piezoelectric plates bordered with viscous and conductive liquid

The influence of a viscous or conductive liquid on the characteristics of acoustic waves propagating in thin piezoelectric plates is investigated theoretically as well as experimentally. Experimental results are found to be in good agreement with the theoretical calculations. The data presented in this paper is essential for the proper design of various acoustic wave sensors operating in contact with viscous and/or conductive liquids.

Characteristics of acoustic plate waves in potassium niobate (KNbO3) single crystal

This paper presents detailed theoretical investigation of three fundamental acoustic wave modes propagating in thin plates of single crystal potassium niobate. The wave velocity and Δv/v, the fractional velocity change produced by electrical shorting of the surface, are calculated for all propagation directions on the surfaces of X-, Y-, and Z-cut plates. It is found that acoustic plate waves can provide extremely large values of electromechanical coupling coefficient. This property makes these waves very attractive for use in a variety of sensor and signal processing applications.

The study of piezoelectric lateral-electric-field-excited resonator

The piezoelectric lateral-electric-field-excited resonator based on an X-cut lithium niobate plate has been investigated. Two rectangular electrodes were applied on one side of the plate so that the lateral electric field components were parallel to the crystallographic Y-axis and excited the longitudinal wave in the gap between the electrodes. The region around the electrodes was covered with a special absorbing varnish to suppress the spurious oscillations. The effect of the absorbing coating width on the resonant frequency and Q-factor of the lateral field-excited resonator was studied in detail with the series and parallel resonances for different width of the gap between the electrodes. As a result, we found experimentally the parameter regions of pure resonances and the boundaries of value variation for resonance frequency, Q-factor, and effective electromechanical coupling coefficient.

Influence of conducting layer and conducting electrode on acoustic waves propagating in potassium niobate plates

The influence of a thin conducting layer and a conducting electrode on the characteristics of acoustic waves propagating in thin plates of potassium niobate is investigated theoretically. The variations in velocity and attenuation as high as 50% and 30 dB per wavelength, respectively, can be achieved for a change in conductance of the thin film layer from 10/sup -7/ to 10/sup -5/ S.

Shear-horizontal acoustic waves in piezoelectric plates bordered with conductive liquid

The influence of a conductive liquid on the characteristics of shear-horizontal acoustic waves of zeroth order (SH/sub 0/ mode) propagating in thin piezoelectric plates of lithium tantalate, lithium niobate, and potassium niobate was investigated. Experimental results obtained for SH/sub 0/ mode devices fabricated on lithium niobate plates are found to be in good agreement with theory. The data presented in this paper is useful for a proper design of various acoustic wave sensors operating in contact with conductive liquids.

The peculiarities of propagation of the backward acoustic waves in piezoelectric plates

The characteristics of backward acoustic waves in piezoelectric plates under different electrical boundary conditions were investigated. It has been shown that electrical shorting of the plate leads to increasing and decreasing the phase velocity for backward and forward branches, respectively. The peculiarities of the hybridization effect of backward waves were studied.

Correspondence - Acoustic waves in a structure containing two piezoelectric plates separated by an air (vacuum) gap

This paper presents experimental results for the characteristics of acoustic waves propagating in a structure containing two parallel piezoelectric plates (I and II) separated by an air gap. Plate I, made of Y-X lithium niobate, contained two interdigital transducers that excited and received an acoustic wave with shear-horizontal polarization. Piezoelectric plate II, made of lithium niobate, was placed above and between the transducers, separated by a fixed gap. For its certain orientation, the amplitude-frequency characteristic showed sharply defined resonant attenuation peaks, which were situated at an equidistant separation from each other. The depth of the peaks was observed to decrease with a wider gap between the plates. It has been stated that these peaks are associated with the resonant reflections of a slot acoustic wave across the width of plate II. Experimentally determined phase velocities and electromechanical coupling coefficient for the slot wave in the structure under study are in a good agreement with theoretical values for various crystallographic orientations of plate II. A comparison between the experimental and theoretical results has allowed us to state two conditions for the slot wave to exist. The structures described may be employed for noncontact excitation of acoustic waves in the plates and for the development of various liquid, gas, and temperature sensors.

Gasoline sensor based on piezoelectric lateral electric field excited resonator

HIGHLIGHTSMeter for analysis of gasoline based on piezoelectric resonator with lateral electric field is developed.Maximal resistance of the electrical impedance of resonator is suitable parameter of sensor.Possibility of considering temperature of gasoline at its analyses is shown.Example of finding octane number of unknown sample of gasoline is shown. ABSTRACT It has been shown that by using piezoelectric lateral electric field excited resonators based on X – cut LiNbO3, one can determine the octane number of gasoline. The measured dependence of gasoline permittivity on its octane number has shown that there is an ambiguous connection between pointed parameters. We have demonstrated both theoretically and experimentally that the value of the real part of the electrical impedance on the frequency of parallel resonance uniquely associates with the octane number of gasoline contacting the free side of the resonator. At that the frequency of parallel resonance does not depend on permittivity/octane number of gasoline. An example of determination of the octane number of a mixture of two different samples of gasoline is given.

Immunodetection of bacteriophages by a piezoelectric resonator with lateral electric field

It has been demonstrated that electroacoustic analysis with polyclonal antibodies can be used for bacteriophage detection. The frequency dependences of the real and imaginary parts of electrical impedance of a resonator with a viral suspension with antibodies were shown to be essentially different from the dependences of a resonator with control viral suspension without antibodies. It was shown that ΦAl-Sp59b bacteriophages were detected with the use of antibodies in the presence of foreign virus particles. The ΦAl-Sp59b bacteriophage content in the analyzed suspension was ~1010–106 phages/mL; the time of analysis was no more than 5 min. The optimally informative parameter for obtaining reliable information was the change in the real or imaginary part of electrical impedance at a fixed frequency near the resonance upon the addition of specific antibodies to the analyzed suspension. It was demonstrated that the interaction between bacteriophages and antibodies can be recorded, offering good prospects for the development of a biological sensor for liquid-phase identification and virus detection.