Ferroelectric Ceramic Plates Research Articles

Transparent for microwave electrodes for applications in nonlinear devices based on ferroelectric ceramic

This article provides the results of an experimental investigation of characteristics of thin-films transparent electrodes deposited on ferroelectric ceramic plates. The experimental investigation of parameters of ZnO and resistive alloy of Si-Ti-Ce deposited on ferroelectric BSTO plates was performed. The influence of transparent electrode deposition on properties of ferroelectric ceramic based on a solid solution of barium-strontium titanate was investigated. The measured low insertion loss of the Si-Ti-Ce thin-film deposited on BSTO ceramic substrate allows considering this material as the perspective for the transparent for microwaves electrodes realization.

Nondestructive Evaluation of Polarization in LTCC/PZT Piezoelectric Modules by Thermal Wave Methods

This work investigates the polarization behavior of low-temperature cofired ceramic (LTCC)/PZT sensor-actuator-modules fabricated by packaging of ceramic PZT plates between alumosilicate-corundum LTCC green layers and subsequent sintering at elevated temperatures. Polarization evaluation was done by applying the laser intensity modulation method (LIMM) where a thermal wave travelling into the ferroelectric PZT ceramic plate is generated by an intensity-modulated laser beam. The penetration depth of the thermal wave was varied with the modulation frequency allowing the separation of pyroelectric response contributions at different regions from the surface to the frequency-dependent penetration depth of the thermal wave.

Electron emission from PZT ceramic with MgO coating layer induced by pulsed electric field

Electron emission into vacuum from PZT ferroelectric ceramic plate coated with MgO thin film has been observed under the application of electric field of pulse consisting of a pair of positive and negative voltages. The damage surface of electrode and PZT ceramic without MgO coating before and after the electron emission has been observed by microscope, and the damage is considered to spread out from the triple point. A high-intensity electric filed exists near the triple point and probably results in the generation of a plasma, which damages the surface of the electrode and makes the electron emission unstable. The MgO coating of the surface of the electrode and PZT has made the emission stable and also enlarged cycles of electron emission.

Electroelastic equations describing slow hysteresis in polarized ferroelectric ceramic plates

Rotationally invariant electroelastic equations are extended to account for slow hysteretic effects in polarized ferroelectric ceramic plates by employing an internal variable in a thermodynamic state function. All material irreversibility is taken to be a consequence of the ferroelectric polarization-electric-field irreversibility. Since we are concerned with the slowest possible hysteresis, we ignore the evolution equation and take the known irreversible thickness polarization-electric-field saturation curve as the starting curve. After the general nonlinear three-dimensional equations are obtained, they are reduced to linear strain and then plane stress because all experimental data available to us are from strain measurements on a thin wide beam forced by voltages applied to very thin polarized ferroelectric ceramic actuators on the surfaces. The new irreversible material coefficients are obtained from data on one major hysteresis loop along with the coefficients in the saturation polarization-electric-field relation. These now known coefficients are then used to calculate other hysteresis loops, which are shown to agree quite well with measurement.

An Analytical Description of Slow Hysteresis in Polarized Ferroelectric Ceramic Actuators

Recently, an existing system of electroelastic equations was extended to account for slow hysteretic effects in polarized ferroelectric ceramic plates by employing an internal variable in a thermodynamic state function. All material irreversibility was taken to be a consequence of the ferroelectric polarization-electric field irreversibility. Since only the slowest possible hysteresis is of concern, the evolution equation is ignored and the known irreversible thickness polarization-electric field saturation curve is taken as the starting curve. Since all experimental data available to us are from strain measurements on a thin wide beam forced by voltages applied to very thin polarized ferroelectric ceramic actuators on the surfaces, the linear strain, plane-stress version of the equations is employed in the description of the actuator. The new irreversible material coefficients for the case of plane-stress are obtained from data on one major hysteresis loop along with the coefficients in the saturation polarization-electric field relations. These now known coefficients are then used to calculate other hysteresis loops, which are shown to agree quite well with measurement.

Field-Excited Electron Emission from ( 1-y)Pb(Mg 1/3Nb 2/3)O 3-yPbTiO 3 Ceramic

Electron emission from a (1-y)Pb(Mg1/3Nb2/3)O3-yPbTiO3 (PMN-PT) ferroelectric ceramic plate has been observed in vacuum by applying a pair of bipolar pulse voltages. The emission is observed even at temperatures above the Curie temperature, as is that of a lead-zirconate-titanate (PZT) ceramic plate. The amount of emitted charge from PMN-PT ceramic is about 5 times larger than that from PZT ceramic, and increases with increasing pulse width. Furthermore, the temperature dependence of the emitted charge suggests that the amount of emitted charge depends strongly on the dielectric constant of the sample. It is considered that the emission is induced by abrupt change of dielectric flux as well as the polarization reversal.

Performance of Multilayered Ultrasonic Transducers Comprising Vinylidene Fluoride and Trifluoroethylene Copolymer Films and Ferroelectric Ceramic Plates

Frequency and impulse response characteristics of multilayered ultrasonic transducers comprising forward films of vinylidene fluoride and trifluoroethylene copolymer (P(VDF-TrFE)) and backward ferroelectric ceramic plates of lead-zirconate-titanate (PZT) and a backing load, are studied both theoretically and experimentally. These transducers can be driven in three operation modes: (1) P(VDF-TrFE) as a transmitter and a receiver, (2) PZT as a transmitter and a receiver, and (3) PZT as a transmitter and P(VDF-TrFE) as a receiver. It is found that, owing to the great difference in their acoustic and dielectric properties, PZT plates and P(VDF-TrFE) films operate independently at different frequencies, and that, in operation mode (3), the multilayered transducers exhibit broad frequency bandwidth or shorter impulse response characteristics with high sensitivity and high S/N ratio.

Electroelastic equations for electroded thin plates subject to large driving voltages

Existing rotationally invariant electroelastic equations are reduced to the case of large electric fields and small strain. These latter equations are specialized to the case of thin plates with completely electroded major surfaces, and it is shown that in this case the charge equation of electrostatics is satisfied trivially to lowest order. It is further shown that for the thin stress-free polarized ferroelectric ceramic plate subject to large electric fields, the resulting equations readily account for experimental data in existence in the literature

Some properties of a plasma generated between two ferroelectric ceramic plates

A plasma was generated in a helium-hydrogen mixture at a pressure of 18 mm of Hg between two periodically (10 kHz) repolarized ferroelectric ceramic plates. Profiles of two HeI- and the H β-lines were measured with spectrometers of different resolutions. For the narrowest line, an interferometric method was applied. The gas temperature ( T g = 480 K) was determined from the Gaussian width of the deconvolved Voigt profile of the HeI 501.6 nm line. The electron temperature ( T e ≈ 16,000 K) was estimated from the line intensities applying appropriate plasma models and the electron density ( n e = 1.4 × 10 14 cm -3) was derived from the half width of the Stark-broadened H β-line.

Birefringent light scattering in PLZT ceramics

A model for visible light scattering in thin, ferroelectric ceramic plates is presented. This and other previously published models are compared with experimental results. An expression for scattered light intensity over exit angle is developed on the basis of multiple refraction from randomly oriented grain and domain walls in a birefringent medium and is compared to measurements of longitudinal-mode light scattering from thin (~250-650-mum) PLZT plates of three different ceramic compositions. The characteristic differences in the observed light scattering are attributed to two physical mechanisms that are related to field-induced ferroelectric anisotropies.

Alignment of Ferroelectric Liquid Crystals on a Ferroelectric Transparent Ceramic Plate

An alignment technique of ferroelectric liquid crystals (DOBAMBC) on a ferroelectric ceramic plate is described. In the cell with a ferroelectric transparent ceramic plate and a buffed glass plate, electric interactions between ferroelectric liquid crystals and a ferroelectric ceramic plate are thought to be effective for aligning liquid-crystal molecules. The result shows that the liquid-crystal molecules orient perpendicular to the polar direction of the transparent ceramic plate.

Sputtered films for display devices

Sputter deposition techniques have been developed which yield directly usable films of transparent conductors and of photoconductors for display devices. These devices have been primarily light-valve structures incorporating a ferroelectric ceramic plate or a liquid-crystal layer as the control medium. The deposition techniques may be modified to allow deposition on a variety of substrates including thermally sensitive materials. Transparent electrodes of sputter-deposited In <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2-x</inf> Sn <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3-y</inf> (ITO) have been deposited on PLZT ferroelectric ceramics, glasses, and other substrate materials. These ITO films have excellent adherence and are hard but may readily be polished and etched. The visible-light transmission is excellent and the absorption in the near infrared is controlled by the conductivity. Films of resistivity of 3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> Ω ċ cm have routinely been deposited on thermally stable substrates while film resistivity of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> Ω ċ cm may readily be obtained on thermally sensitive substrates. Sputter-deposited CdS, which has a peak photosensitivity near the 514.5-nm line of the Ar laser, has had a photoconductive gain of 4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> and a dark resistivity greater than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> Ω ċ cm. Similar sputter-deposition techniques have been used to fabricate device structures incorporating Cd <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> Zn <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> S as the photoconductor. The Cd <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> Zn <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> S composition has been varied to match film peak photosensitivity with laser emissions between 400 and 500 nm. These films have not been as photosensitive as CdS but they permit greater visible-light transmission, are sufficiently insensitive to projecting light sources so that they may be used in simultaneous read-write systems, and are capable of being used in real-time display systems. The dark resistivity of Cd <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> Zn <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> S is dependent on composition but has exceeded 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> Ω ċ cm in all films.

Sputter-deposited films for display devices

Many of the electrode requirements of sandwich structure light valve devices using either ferroelectric ceramic plates or liquid crystal layers as the control medium have been satisfied by sputter-deposited layers. The sputtering parameters can be modified to allow film deposition within the constraints of a given substrate material such that useful photoconductive layers are obtained on thermally sensitive as well as thermally stable substrates. The use of Cd 1− x Zn x S films permits selection of the photoconductivity peak to match the specific emission of a laser. These Cd 1− x Zn x S films also permit greater visible light transmission, can be relatively insensitive to projection light, posses dark resistivity in excess of 10 12ohms cm and are suited to real-time display applications. Sputter-dedeposited layers of CdS, though of narrower band gap than Cd 1− x Zn x S, can be deposited with photoconductive gain of the order of 4 × 10 3 and dadrk resistivity in excess of 10 7 ohms cm. Transparent electrodes of sputter-deposited In 2− x Sn x O 3− y have excellent mechanical, elecrrical and optical properties. Routine deposition of films with less than 3×10 −4 ohms cm resistivity on thermally stable substrates and with resistivity less than 10 −3 ohms cm on thermally sensitive substrates has been demonstrated.

Transverse surface wave as high-frequency limit of a shear-horizontal piezoelectric plate wave

It is hown that the lowest symmetric shear horizontal plate mode in a width-polarized ferroelectric ceramic plate becomes a double transverse-surface (Bleustein) wave when the wavelength is small compared with the plate thickness. The frequency equations for the above plate wave are derived for different boundary conditions, as well as their surface-wave approximations. Numerical solutions are used to determine the behavior of the wave at all frequencies.

Improved Aging and Switching of Lead Zirconate-Lead Titanate Ceramics with Indium Electrodes

After repeated switching, ferroelectric ceramic plates will exhibit aging evident in hysteresis loops as a marked decrease in remanent polarization (Pr) and an increase in coercive field (Ec). A hot-pressed ceramic having a composition of 65% lead zirconate-35% lead titanate with 2 at.% lanthanum and having a grain size 2 μ or less was used to study the effects of various electrode materials. The source disks were polished down to a thickness of 25, 37, or 63 μ and square plates 2.5 mm on edge were cut for testing. Prior to the application of the electrodes, the square plates were annealed in air at 700°C for 10 min and cooled slowly to room temperature. Electrodes were then applied as opposing disks 1.5 mm in diameter on the surfaces of the plates. A Sawyer-Tower circuit was used to observe hysteresis loops formed on an oscilloscope at a frequency of 60 Hz, and occasionally at 600 Hz. Maximum applied voltage corresponded to approximately 3Ec. Results were obtained for vapor plated electrodes of Al, Cr–Au, Pb, PbO–Ag, Sn–Ag, Ag, Ga, and In. For all but the In electrodes, a large decrease of Pr was evident by 107 cycles. The In electrodes yielded lower values of Ec (approximately 8 kV/cm) and the value of Ec did not increase appreciably over the test period. After 109 cycles, Pr had decreased by only 14% for the In electrodes.

Ferroelectric ceramic light gates operated in a voltage-controlled mode

Plates of lead zirconate-lead titanate ferroelectric ceramic can have 1) low-loss optical transmission in thin, polished sections and 2) uniaxial birefringence dependent upon remanent polarization. These properties are potentially useful in electrically variable optical retarders, modulators, and latching light gates. This paper reports the results of measurements of basic light-gate devices using ferroelectric ceramic plates. A number of characteristics of the devices are reported; e.g., dependence of absolute light phase retardation on ceramic remanent polarization; dependence of ON-OFF ratio on exit aperture, switching pulse duration, and light wavelength; switching speed; and the dc hysteresis characteristic of the dependence of remanent polarization upon applied field. In the past, the use of ferroelectric devices under conditions producing partial switching has been discussed exclusively from the point of view of "charge-limited switching." This paper proposes a new mode of operating ferroelectric ceramic light gates using "voltage-controlled switching." Charge-limited switching results naturally when voltage pulses of short duration are used (appreciable ON-OFF ratios can be obtained from a light gate switched with pulses as short as 10 ns). As a result of the hysteresis in the dc switching characteristic, pulses with durations of the order of milliseconds or longer result in operation of the light gate in a voltage-controlled mode. Practical advantages resulting from this mode of operation are discussed.