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A compact hardware-software complex for measuring the electrical and mechanical parameters of a liquid based on a piezoelectric resonator with a lateral exciting electric field has been developed. It is shown that the modulus of the electrical impedance of the resonator near the resonant frequency decreases monotonically with an increase in conductivity of the contacting liquid. The obtained dependences can be used as calibration curves for measuring conductivity in the range of 100-10,000 μS/cm. A method for the simultaneous determination of the modulus of elasticity, viscosity, and permittivity of a liquid using the electromechanical equivalent scheme was developed and tested on a mixture "water - glycerol" with the different glycerol content.

As known, anomalous resisto-acoustic effect is a fundamental property for weakly inhomogeneous piezoactive waves (Bleustein-Gulyaev, Love, and some leaky waves). It consists in that the velocity of aforementioned waves first increases, achieves its maximum, and only then decreases with increasing conductance of a layer placed at the surface of piezoelectric half-space. In this paper we continue to study the peculiarities of the effect appearance and the influence of different electrical boundary conditions on its characteristics. Conditions have been found under which the said effect appears and, respectively, disappears. The magnitude of positive change in velocity with increasing layer conductance is demonstrated to be reduced up to zero as a layer with arbitrary conductance has been moved away from the piezoelectric surface. The positive change in velocity increases when an perfectly conductive screen moves away from the "piezoelectric half-space - conductive layer" structure. The obtained results are useful for a more deep understanding the physical basis of propagation of weakly inhomogeneous piezoactive acoustic waves (Bleustein-Gulyaev, Love, and some leaky waves).

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.

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.

This paper presents new principles which allow the measurement of all the parameters of powerful short-duration single microwave pulses generated by relativistic electronic generators by using only one pulse. These principles, based on excitation and propagation of surface and bulk acoustic waves, have allowed us to develop new devices for measuring electric and magnetic field intensity, duration, and carrier frequency of such pulses.

The paper presents theoretical results for the effects of differently oriented external electric field on the velocity of Bleustein-Gulyaev surface acoustic waves (BG SAW) in lithium niobate and strontium titanate for different mechanical crystal states. It has been revealed that the BG SAW is unstable towards external effects, i.e. that the electric field not only alters its velocity, but it also yields the wave direction displacement. It is shown that, unlike the Rayleigh wave, the BG SAW exhibits a wave localization depth which substantially depends on the external effects.

This paper presents a detailed theoretical and experimental investigation of quasi shear horizontal (QSH) acoustic waves in thin plates of lithium niobate. Properties that have been studied include electromechanical coupling coefficient, dispersion characteristics, temperature coefficient of delay, and influence of a biasing electric field on the wave velocity. All propagation directions in X , Y , and Z -cut plates have been investigated. The QSH wave can provide very high electromechanical coupling. Values of coupling coefficient K 2 as high as 0.36 can be obtained for waves propagating in the X direction of Y -cut lithium niobate plates. The nearly non-dispersive propagation, the large K 2 value, and the ability to propagate in contact with a liquid medium makes the QSH wave attractive for use in a variety of sensing and signal processing applications. The data presented in this paper is essential to optimize the design and performance of QSH wave devices.

It has been shown recently that an acoustic wave which is nearly polarized in the shear horizontal direction can exist in thin plates of arbitrary elastic materials if the ratio (h is the plate thickness, the acoustic wavelength) is less than unity. We refer to this as a QSH (quasi-shear-horizontal) acoustic wave. Preliminary results showing attractive properties of this wave have been published. This paper presents detailed theoretical and experimental investigation of QSH waves in thin plates of lithium niobate. Results confirm that the QSH wave provides a number of attractive properties for use in sensing and signal processing applications. These include the following: (i) a phase velocity nearly constant for all values of ; (ii) the ability to propagate in contact with a liquid medium and (iii) a very high value of electromechanical coupling coefficient. Experimental measurements of phase velocity and coupling coefficient are found to be in good agreement with theoretical calculations. The influence of a biasing electric field on the propagation of QSH waves has been calculated. It is shown that biasing voltages of less than 200 V can produce fractional time delay changes greater than 0.15% in QSH wave delay lines fabricated on thick lithium niobate plates.

The reflection of ultrasonic Lamb waves produced by a periodic array of thin conducting strips deposited on a piezoelectric plate was investigated both theoretically and experimentally. A repetitively mismatched transmission line model was used to analyze the performance of the reflector. The reflection coefficient of a single strip is given by R/spl ap//spl Delta/v/v, where /spl Delta/v/v is the fractional change in velocity produced by electrical shorting of the propagation surface. An attractive property of Lamb waves is that they can provide a much higher value of /spl Delta/v/v than is possible with surface acoustic waves. Therefore, efficient Lamb wave reflectors can be realized with relatively few strips in the reflector. For example, reflection coefficient very close to unity, R/spl ap/0.98, has been obtained in a Lamb wave reflector consisting of just 12 strips on a Y-X lithium niobate plate. The reflector has been used to realize a unidirectional transducer (UDT). A Lamb wave delay line consisting of two UDTs shows insertion loss of less than 3 dB with fractional bandwidth greater than 7%.

The behavior of acoustic axes and conical refraction are analyzed for lithium niobate and strontium titanate crystals, which are either mechanically squeezed or mechanically free and placed in an external electric field. Relying on numerical calculation, field dependencies of the acoustic axis shift and splitting angles have been elaborated, which are compared with the results obtained previously in the context of the theory of perturbations. External electric fields with the intensity E

The characteristics of QSH (quasi shear horizontal) acoustic waves propagating in thin plates of Y-cut, X-propagation lithium niobate are investigated theoretically and experimentally. The fractional velocity change (/spl Delta//spl nu///spl nu/) produced by electrical shorting of the surface is calculated as a function of the normalized plate thickness h//spl lambda/ (h=plate thickness, /spl lambda/=acoustic wavelength). It was found that values of /spl Delta//spl nu///spl nu/ as high as 0.18 could be obtained. Experimental measurements show good agreement with theory. The properties of QSH waves propagating in the presence of a perfectly conducting electrode separated from the piezoelectric plate by a small air gap have been studied theoretically and experimentally. It was found that by varying the height of the gap, the phase shift through a 3.2-MHz QSH wave delay line can be varied by more than 230/spl deg/. We have also theoretically investigated the influence of a thin layer of arbitrary conductivity on the velocity and attenuation of the QSH wave. Calculations show that the variations in these parameters can be as high as 18% and 5 dB per wavelength for a change in layer surface conductance from 10/sup -7/ to 10/sup -5/ S. Results obtained in this paper confirm the attractive properties of QSH waves for a variety of sensing and signal processing applications.

The modulus of elasticity and coefficients of viscosity of nanocomposite films with various percentages of nanoparticles of Fe and CdS in the matrix of low-pressure polyethylene are investigated. For measuring we used the appropriate resonators with longitudinal or shear acoustic waves loaded by the film under study. The calculation of resonator impedance was carried out by the method of equivalent circuits. By using the least-squares method and variation of modulus of elasticity and coefficients of viscosity of the nanocomposite film the calculated frequency dependencies of real and imaginary parts of impedance of loaded resonator were fitted to experimental ones. Key words: Nanocomposite films, modulus of elasticity, coefficients of viscosity, method of equivalent circuits A. Introduction Over the long time the researchers and designers of the electronic devices have given much attention to finding the new physical principles of creation of the artificial electronic media. At present time the new approaches in creation of such media have become to be possible due to the development of nano-technology. One of the important directions of development of nano-technology is the creation and investigation of nanocomposites based on nanoparticles of metals and their compounds, which are stabilized in the volume of polymeric dielectric matrix [1]. The use of the polymeric materials as matrix stabilizer of nanoparticles opened the new scientific direction, namely the plastic electronics. Earlier [2] it has been shown that the properties of metallized nanocomposite materials depend on the volume concentration of nanoparticles by critical way. The change of the concentration of nanoparticles respectively to polymeric matrix stabilizer significantly influenced on the main parameters of nanocomposite: electric conductivity, complex dielectric permittivity, plasma frequency, etc. The variation of mixture of nanocomposite by the change of type of dielectric matrix, size, composition and concentration of nanoparticles allows to purposefully control the basic physical properties of nanocomposite: electrical, optical, mechanical, etc. But at present time there is not the detailed information about elastic properties of developed polymeric composite nanomaterials. Just recently the paper devoted by the investigation of density, phase velocity, and acoustic impedance of alumina colloidal/polymer composite film has been published. In this connection the paper is devoted to experimental investigation of modulus of elasticity and coefficients of viscosity of some nanomaterials with various concentration of nanoparticles of Fe and CdS in polymeric matrix.

This paper describes development of a novel, high efficiency transducer for use in ultrasonic flow meters. It is based on conversion of energy between surface acoustic waves (SAWs) and bulk acoustic wave (BAWs). The transducer consists of thin plate of a suitable piezoelectric material whose SAW velocity is greater than velocity of BAW in the fluid. Under these conditions a surface wave traveling on the substrate radiates a bulk acoustic wave in the fluid. We show that with proper design efficient conversion of energy from SAW to BAW and vice versa can be obtained. For example. using lead zirconate titanate (PZT) as the piezoelectric material and water as the fluid, total conversion loss (SAW to BAW and back from BAW to SAW) of less than 3 dB has been obtained.

This paper presents theoretical and experimental study of QSH waves propagating in thin plates of lithium niobate. The electromechanical coupling coefficient K/sup 2/ has been calculated as a function of plate thickness and propagation direction for all main crystallographic cuts. Y-cut and X-propagation for which K/sup 2/ may be more than 30% were chosen for our experiments. We have measured K/sup 2/ as a function of plate thickness and have obtained a good agreement with theory. The extremely large value of K/sup 2/ opens possibility of realizing devices whose parameters can be controlled by electrical boundary conditions. We have studied SH waves propagating in the presence of a conducting electrode. It is found that by varying the gap between plate and electrode, the phase shift for a 3.2 MHz delay line can be varied by as much as 240/spl deg/. We have also studied the influence of a thin layer of arbitrary conductivity on the velocity and attenuation of the QSH wave. Analysis show that the variations in these parameters can be as high as 18% and 4 dB//spl lambda/ for a change of surface conductivity from 10/sup -7/ to 10/sup -5/ S.

This paper presents the first report on the reflection of ultrasonic Lamb waves produced by a periodic array of thin conducting strips deposited on a piezoelectric plate. A repetitively mismatched transmission line model was used to analyze the performance of the reflector. The reflection coefficient of a single strip is given by r/spl ap//spl Delta/v/v, where /spl Delta/v/v is the fractional change in velocity produced by electrical shorting of the surface. An attractive property of Lamb waves is that they can provide a much higher value of /spl Delta/v/v than is possible with surface acoustic waves. Efficient Lamb wave reflectors can therefore be realized with relatively few strips in the reflector. Experimental results obtained with a number of Lamb wave reflectors confirm this hypothesis. For example, reflection coefficient very close to unity, R/spl ap/0.98, has been obtained in a SH wave reflector consisting of just 12 strips. To obtain comparable reflection with SAWs, one would need to use more than 70 strips. Details of the theoretical analysis used and experimental results obtained will be presented.

Describes the use of bulk acoustic waves to measure elastic and viscous properties of thin dental resin films. Our initial experiments have utilized a 7.3 MHz bulk longitudinal wave resonator fabricated on a Z-cut lithium niobate plate. At first, the frequency dependence of resonator impedance (without resin coating) was measured. This was used to determine effective material constants of the resonator by performing a least-squares fit of measured data with theoretically calculated values. One surface of the resonator was then coated with a thin film of the resin under study. The effect of the coating is to lower the resonant frequency and the quality factor of the resonator. The change in these parameters can be used to calculate the elastic constant C/sub 11/ and viscosity constant /spl eta//sub 11/ of the resin film. The elastic constant C/sub 44/ and /spl eta//sub 44/ were similarly determined using a shear wave resonator fabricated on an X-cut lithium niobate plate. Our measurements indicate that mechanical properties of the resin film are a function of the film thickness. Possible reasons for this behavior are discussed. The techniques described here allow one to determine the mechanical properties of dentin resin films. This information is essential in order to understand the clinical behavior of these materials.

The reflection of ultrasonic Lamb waves produced by a periodic array of thin conducting or mass loading strips is investigated both theoretically as well as experimentally. A repetitively mismatched transmission line model is used to analyze the performance of the reflector. It is found that Lamb waves propagating in thin elastic plates can be reflected much more efficiently than surface acoustic waves (SAWs). Efficient reflectors can therefore be realized with relatively few strips in the array. The characteristics of a number of reflectors fabricated on thin plates of lithium niobate have been evaluated and found to be in good agreement with theory. The reflectors have been used to realize various useful devices such as unidirectional transducers, low loss, wide bandwidth delay lines, and Lamb wave resonators.

The characteristics of acoustic waves propagating in thin plates of single crystal potassium niobate are theoretically investigated. It is found that acoustic plate waves can provide extremely high values of electromechanical coupling. For example, values of Δv/v, the fractional velocity change produced by electrical shorting of the surface, as high as 0.5 can be obtained with the shear horizontal (SH0) wave. The influence of a thin conducting layer on the velocity and attenuation of plate waves is investigated. It is shown that variations in these parameters as high as 50% and 30 dB per wavelength can be achieved for change in layer sheet conductance from 10-7 to 10-5 S.

The influence of a thin layer of arbitrary conductivity on the characteristics of acoustic waves in potassium niobate is investigated theoretically. The conductivity of a thin layer on the surface of a potassium niobate crystal or plate is shown to have a significant influence on the damping and velocity not only of symmetric Lamb waves and quasi-shear-horizontal waves but also of Gulyaev-Bleustein waves. It is found that a relative change in velocity as large as 50% can be achieved for quasi-shear-horizontal waves by altering the surface conductivity. The results obtained reveal great prospects of using potassium niobate to create acoustoelectronic devices with controllable characteristics.

It has been found that variations in the electrical boundary conditions can significantly change the structure of surface acoustic waves propagating in potassium niobate. For example, a generalised Rayleigh wave propagating along the X+15/spl deg/ direction in the Y-cut may be transformed into a quasi-shear Bleustein-Gulyaev wave by electrical shorting of the surface.

The characteristics of acoustic waves propagating in thin plates of single crystal potassium niobate (KNbO3) have been theoretically investigated. It is found that acoustic plate wave modes can provide much stronger electromechanical coupling (ΔV/V = 0.51) than is possible with surface acoustic waves (ΔV/V = 0.265).

The influence of a thin conducting layer on the propagation of surface acoustic waves in a piezoelectric medium is investigated theoretically. It is generally believed that wave velocity decrease monotonically with increasing conductance of the layer. Our calculations show, however, that in the case of weakly inhomogeneous surface waves, such as Bleustein-Gulyaev and Love waves, there exists a certain conductance interval in which the wave velocity increases with increasing layer conductance. This anomalous behavior, referred to as the anomalous resisto-acoustic effect, is related to the penetration depth of the wave into the substrate. The anomalous effect is present if the penetration depth exceeds a certain critical value, and absent otherwise. The anomalous effect allows one to obtain value of /spl Delta/v/v, the fractional velocity change, that is greater than the normally predicted value of /spl Delta/v/v=(v/sub 0/ -v/sub m/)/v/sub 0/. For example, for Bleustein- Gulyaev waves propagating in Y-cut, X-propagation potassium niobate, values of /spl Delta/v/v greater than 0.32 can be obtained, compared to the normally predicted value of 0.26.

This paper is concerned with the influence of a viscous liquid on the propagation of acoustic waves in thin plates of lithium niobate. The characteristics of the three lowest order wave modes that such a plate can support (zeroth order antisymmetric Lamb wave A/sub 0/, symmetric Lamb wave S/sub 6/, and quasi-shear-horizontal wave QSH/sub 6/) are investigated. It is assumed that the liquid is isotropic such that its viscous properties are described by two independent components of viscosity tensor /spl eta//sub 11/ and /spl eta//sub 44/. It is found that the attenuation of the waves depends primarily on the shear component of viscosity /spl eta//sub 44/. The influence of expansion component /spl eta//sub 11/ is negligible. The attenuation per unit length is proportional to (/spl eta//sub 44/)/sup 1/2 / and f/sup 1,3/, where f is the frequency of the wave. Under identical conditions, the lowest value of attenuation is for the S/sub 0/ mode, while the highest is for the A/sub 0/ mode. For example, for h//spl lambda/=0.025 (h=plate thickness, /spl lambda/=acoustic wavelength) and /spl eta//sub 44/=0.003 Ns/m/sup 2/, the attenuation in dB/cm at a frequency of 1 MHz for A/sub 0/, S/sub 0/ and QSH/sub 0/ modes is 13.5, 0.024, and 0.073, respectively. The above results indicate that the S/sub 0/ wave is most suitable for use in devices operating in contact with a viscous liquid. The results also show that by using the three different wave modes, one can develop a viscosity meter with a very wide measurable range of viscosity.