Kohji Toda

Acoustic wave characteristics of lead-free (Bi1/2Na1/2)0.99Ca0.01TiO3 piezoelectric ceramic

Acoustic wave characteristics of lead-free (Bi1/2Na1/2)0.99Ca0.01TiO3 (BNC-1) piezoelectric ceramic are studied from a viewpoint of a new substrate material group for a surface acoustic wave and/or a bulk acoustic wave. The BNC-1 ceramic, which has high electromechanical coupling factors, k33(=37.6%) and kt(=51.3%), and low free permittivities, e33T/e0(=236) and e11T/e0(=271), along with a high mechanical strength, is favorable to high frequency ultrasonic uses. Two interdigital transducers can excite an SH plate mode wave or a Lamb mode wave whose travelling direction is perpendicular or parallel to the poling axis, respectively. A delay line type oscillator using the SH wave is demonstrated a single mode oscillation of 8.319 MHz.

Piezoelectric Properties of Bismuth Layer-Structured Ferroelectric Na0.5Bi4.5Ti4O15 Ceramic

Piezoelectric properties of the grain-oriented Na0.5Bi4.5Ti4O15 (NBT) ceramic, belong to the bismuth layerstructured ferroelectric (BLSF) ceramics are studied from applicational viewpoints on grain orientation prepared by the hot-forging (H.F.) method. The MnCO3 (0.1 wt%) doped NBT (NBT+Mn(0.1)) ceramic can stand the high temperature poling process, because of the high resistivity. The grain orientation (H.F.) makes the piezoelectric properties of NBT+Mn(0.1) ceramic much more pronounced than those of the non-oriented (O.F.) ceramic. Coupling factors k33 and k15, along with piezoelectric constants d33, d15, g33 and g15, of the H. F. NBT+Mn(0.1) ceramic are enhanced, and their anisotropies in k33/k31 and k15/k24 are emphasized. A bulk wave delay line oscillator using the ceramic substrate is demonstrated.

Determination of the crystal structure of Pb2CrO5

The crystal structure analysis of Pb2CrO5 is determined by comparison with powder x‐ray and electron diffraction data. The structure is monoclinic: c2/m. All of the atom positions are determined by considering the calculated values of d spacings, line intensities, bond lengths, and bond angles. A new set of lattice parameters are a=14.018, b=5.683, c=7.143 A, and β=115.23 °. A preliminary result on photoconductivity in a Pb2CrO5 ceramic disk is also given.

Electrical, optical and acoustic properties of PLZT ceramics by two-stage processing

Abstract A new sintering technique for transparent PLZT ceramics was developed which uses a unique two-stage process involving both vacuum hot pressing for a short time (first stage) and atmosphere sintering (second stage). By this process we obtained highly transparent, virtually colorless, and extremely pore-free PLZT 9/65/35. The quality of materials fabricated by this process depends strongly upon the method of controlling the liquid phase excess lead oxide in the grain boundaries.

Analysis of performance of leaky lamb wave transducer operating at liquid-solid interface

The propagation characteristics of a leaky Lamb wave transducer built from a thin piezoelectric plate with interdigital electrodes are numerically analyzed under the condition of operating at a liquid-solid interface. The phase velocity, electromechanical coupling constant, and efficiency for acoustic beam radiation into water are given as a function of the product of the frequency and the substrate thickness. Numerical results are well confirmed experimentally.

Liquid Viscosity Measurement Using SH Wave Propagation Characteristics on Piezoelectric Ceramic Thin Plate

Liquid viscosity measurement using shear horizontal (SH) wave propagation characteristics on a piezoelectric ceramic thin plate is described. The mode conversion loss associated with the compressional component U3 is zero, because the SH wave on the piezoelectric ceramic substrate poled along the horizontal axis has only the horizontal component U2, The IDT has a much larger electromechanical coupling factor for the S0 mode SH wave than that of the SH surface acoustic wave (SAW). The metal-coated condition of the liquid-loaded surface is essential for detecting the liquid viscosity. There exists a linear relationship between the fractional phase velocity change of the S0 mode and the square root of the liquid viscosity. The measured results on liquid viscosity using the S0 mode SH wave devices, for some concentrations of glycerol-water solutions, are in good agreement with the theoretical prediction.

Photovoltaic effect in Pb2CrO5 ceramic

The existence of the photovoltaic effect has been observed in Pb2CrO5 ceramic. A typical photosensitive device has one pair of surface electrodes on one surface of a ceramic disk. The illumination response of the photovoltage in the device is described with the measured relation between the photovoltage and the illuminated area. The spectral photovoltaic response of the device has a peak sensitivity around 5700 A in the visible region.

Evaluation of nematic liquid-crystal director-orientation using shear horizontal wave propagation

The nematic liquid-crystal director-orientation in the vicinity of the interface between a liquid-crystal layer and a glass substrate is evaluated in various orientations under an applied electric field, using shear horizontal (SH) wave propagation. The measured acoustic phase delay is related to numerical analysis of the propagation characteristics of the SH wave in a trilayer structure containing a nematic liquid-crystal layer (4-cyano-4′-pentylbiphenyl: 5CB) between two glass plates. This technique using SH wave propagation in a liquid-crystal cell is promising for evaluating the nematic liquid-crystal director angle in the vicinity of the interface.

A Lamb wave voltage sensor

A voltage sensor using a Lamb wave delay line oscillator is described. The device consists of two pairs of interdigital transducers and one plate electrode at the central part of the device. All of these transducers have the counter electrodes on the bottom surface of the substrate. The oscillation frequency of the device changes significantly with the voltage applied to the central plate electrode. Performances of the voltage sensor are given, including sensitivity and its frequency dependence.

Viscosity Measurement of Ferroelectric Liquid Crystal Using Shear Horizontal Wave Propagation in a Trilayer Structure

Propagation characteristics of a shear horizontal (SH) wave in a trilayer structure, having a viscous liquid layer between a piezoelectric ceramic plate and a glass plate, are described on the basis of numerical and experimental investigations. Viscosity dependences of mechanical displacement distributions and relationships between the fractional velocity change and the square root of viscosity are discussed. The viscosity is related to the acoustic phase delay, accompanied by the SH wave propagation, between two interdigital transducers on the SH wave device. The measured temperature dependence of viscosity of silicon oil is in good agreement with the numerical analysis result of the SH wave propagation. An electrorheology effect and the temperature dependence of the viscosity in a ferroelectric liquid crystal (FLC: CS1014) are also measured by this technique.