Pyroelectric Applications Research Articles

Ferroelectric ceramics and thin films for pyroelectric applications

Abstract The extensive work carried out at Caswell in recent years on ferroelectric ceramics for pyroelectric applications is reviewed briefly. With the ultimate aim of fully CMOS compatible integrated thermal detectors and imagers, pure and lanthanum doped lead titanate thin films have been deposited using the emerging PVD technique of dual ion beam sputtering (DIBS). The DIBS process produces high quality orientated perovskite films. Films have been formed at 500–600°C onto sapphire, MgO and silicon substrates by sputtering from an adjustable composite PLZT ceramic/Ti and Pb metallic target. Some substrates were coated with platinum/titanium prior to deposition to allow longitudinal electrical measurements to be made on the films. On silicon, the platinum/titanium electrodes were found to blister during the PLZT thin film deposition process. Pure and 7% lanthanum doped lead titanate films have shown pyroelectric effects with coefficients in the range 0.5–4.0 × 10−4 Cm−2 K−1 and a figure of merit of 2.6 ...

Electro-Active Polymer-Ceramic Composites for Piezoelectric and Pyroelectric Applications

AbstractPresent work reports the results of a study of characterization of dielectric, piezoelectric and pyroelectric properties of calcium modified lead titanate ceramic/poly (vinylidene-trifluorethylene) composites with zero-three connectivity. The paper also presents a theoretical model to optimize such properties with respect to particle size, dielectric constant and composition.

Lead scandium tantalate -lead titanate materials for field -stabilized pyroelectric device applications

Abstract A preliminary evaluation of the pyroelectric response of selected compositions from the variable order-disorder [VOD] phase region of this system has been conducted under modest DC biasing conditions in order to assess the performance of these materials for application in small area pyroelectric devices. The figure of merit [FD] was observed to be significantly enhanced over that of the pure Pb(Sc½Ta½)O3 material due to the combined effects of Ti doping, ordering, and the application of a biasing field.

PbTiO3ferroelectric thin films and their pyroelectric application

Abstract A series of technical data for preparing PbTiO3 and La-modified PbTiO3 films by using various deposition methods such as rf sputtering and chemical vapor deposition are described. The resulting thin films show very good ferroelectric, pyroelectric, piezoelectric and electro-optic properties. Infrared sensors using the films show good voltage responsivity, detectivity and fast response, and, in particular, c-axis oriented films have excellent characteristics. The film prepared on Si wafers can be directly combined with active devices such as FET's and bipolar transistors. Sensitivity of the films on Si and MgO substrates has been increased considerably by removing the substrate beneath the sensitive area with chemical etching. Linear and two-dimensional arrays have been developed on some types of the substrates and their basic characteristics have been investigated for improving sensitivity resolution. Infrared imaging has also been tried by using the array sensors.

Pyroelectric properties of lead barium niobate single crystals

Abstract The temperature dependence of the pyroelectric coefficients of lead barium niobate Pb1−xBaxNb2O6 (PBN) single crystals were investigated using the Byer-Roundy technique. Pyroelectric coefficients were found to be enhanced in single crystals of the near-morphotropic phase boundary (MPB) compositions. High pyroelectric coefficients (336 μC/m2−K, 1 − × = 0.684) and switchable polarization vectors between the two perpendicular crystallographic directions ([001] and [110]) in crystal of near-morphotropic phase boundary composition (1 − x = 0.615) were found to be of interest for pyroelectric device applications.

Pyroelectric properties and applications of piezoelectric PLZT ceramics

Abstract Pyroelectric and dielectric properties of piezoelectric ceramics have been studied in the broad temperature range 293–483 K. The effect of gamma (γ)-irradiation on the pyroelectric coefficient and figure of merit of piezoceramic samples has been examined for the smeared phase transition region. The results obtained are discussed in the framework of the model of “quasiferroelectricity.” It is shown that PLZT-6 type piezoceramics produce stable performance pyroelectric devices when exposed to large γ-irradiation doses.

Pyroelectricity in some ferroelectric semiconductors and its applications

Abstract The distinct features of pyroelectric studies of ferroelectric semiconductors (FES), by a dynamic method, are considered. The influence of illumination, external electric field and various thermal cycles on the pyroelectric response of FES are analyzed. The efficiency of FES, such as Ag3AsS3 and Sn2P2S6, for pyroelectric applications are demonstrated. The practical realization of the potentiality of FES for such purposes are discussed.

Properties and applications of ferroelectric and piezoelectric thin films

Polar axis oriented films are important in piezoelectric, pyroelectric, optic, and ferroelectric applications. The applications of polar axis oriented films are reviewed. An acousto-optic deflector made of ZnO thin film optics and Si Schottky diode photo-detectors integrated on a Si substrate is described. The properties mainly related to the integrated memory applications of polar axis oriented ferroelectric films grown by reactive magnetron sputtering are reported.

Ferroelectric and structural properties of the tungsten bronze system K 2Ln 3+Nb 5O 15, Ln = La to Lu

The K 2Ln 3+Nb 5O 15 system has been investigated for a range of rare-earth ions (La 3+ to Ho 3+, Y 3+). The temperature-dependent dielectric properties indicate that all but the La 3+-containing materials have a tungsten bronze orthorhombic structure. Two phase transitions occur above room temperature, one paraelectric:ferroelectric and the other ferroelectric:ferroelastic. These transitions shift toward higher temperatures as the size of the rare-earth ion decreases. The lattice constant determination for this system indicates that the larger ions (La 3+ to Gd 3+) predominantly prefer the 12-fold coordinated site, Tb 3+ to Ho 3+ are distributed over both the 12- and 9-fold coordinated sites, and the smaller rare-earths (Er 3+ to Lu 3+) do not yield the tungsten bronze phase. Because of their low dielectric constants, these bronzes appear to be promising for some optical and pyroelectric detector applications.

Ferroelectric Pb(Zr, Ti)O 3 thin films by reactive sputtering from a metallic target

Perovskite phase Pb(Zr, Ti)O 3 films have a variety of ferroelectric, piezoelectric and pyroelectric applications, including use in non-volatile semiconductor memory devices. We have formed ferroelectric perovskite Pb(Zr, Ti)O 3 thin films by dc magnetron sputtering from a metallic target in an oxygen-doped argon atmosphere. Post deposition annealing at 550 to 600°C produces a film with the perovskite structure. The resulting film shows ferroelectric switching. Switching thresholds as high as 30 μC cm −2 have been obtained. Auger electron spectroscopy shows that these films have a composition near the morphotropic phase boundary ( Zr/ Ti=52/48).

Polar Langmuir-Blodgett thin film layers for non-linear optical and pyroelectric applications

Abstract Advances in the synthesis of non-centrosymmetric molecules coupled with the recently acquired ability to incorporate them into stable three dimensional arrays with a high degree of order, holds out exciting possibilities for the development of high quality, low cost organic materials for a variety of applications. Langmuir-Blodgett (LB) films possessing a unique polar axis can be fabricated by depositing head to tail sequences of a specially designed molecule or better still by forming organic superlattices (alternate layers of different molecules) using purpose built equipment. Two device areas of particular interest that capitalize on this ability to form supermolecular assemblies are optoelectronics and pyroelectricity. This paper reviews the efforts that have been made in engineering molecules so as to optimize their non-linear properties. In the optics field, most attention has been placed on materials designed specifically for second harmonic generation applications. For thermal imaging pur...

Ferroelectric Properties of Tungsten Bronze Morphotropic Phase Bounary Systems

Tungsten bronze ferroelectrics which have a morphotropic phase boundary (MPB) can have a number of enhanced dielectric, piezoelectric, and electrooptic properties compared to more conventional ferroelectric materials. The structural and ferroelectric properties of several MPB bronze systems are presented, including data from sintered and hot‐pressed ceramics, epitaxial thin films, and bulk single crystals. Included among these are three systems which had not been previously identified as morphotropic. The potential advantages and limitations of these MPB systems are discussed, along with considerations of the appropriate growth methods for their possible utilization in optical, piezoelectric, or pyroelectric device applications.

Tungsten bronze crystals for photorefractive self-pumped phase conjugation

Abstract We review the current status of photorefractive self-pumped optical phase conjugation in the tungsten bronze family of ferroelectric crystals. The tungsten bronze ferroelectrics have emerged as an important class of materials for performing optical phase conjugation in addition to the well known pyroelectric, piezoelectric, and electro-optic applications. The large electro-optic coefficients, open lattice structure, compositional flexibility, and good optical quality of these materials has made possible a new set of self-pumped phase conjugate mirrors. Our initial interest in this class of crystals arose from a number of enlightening discussions with Professor L. Eric Cross who pointed out the multitude of applications possible with the tungsten bronzes. We would like to acknowledge his assistance and encouragement by dedicating this paper to Professor Cross on the occasion of his 65th birthday.

The influence of the preparation method on the properties of Sr 8(Al 12O 24)(CrO 4) 2 ferroelectric ceramics

Strontium-aluminate-chromate (SACR) ceramics have been prepared by the citrate method. As a result the sintering temperature was reduced from 1700°C (in conventional oxide method) to 1500°C. These ceramics reveal a new phase transition. The dielectric and pyroelectric measurements show that SACR is an important candidate material for pyroelectric applications. The two phase transitions observed in the present study can be useful to enhance the figure of merit of a device at room temperature.

Ferroelectric Ceramics for Dielectric Electromechanical and Pyroelectric Applications

The growth of integrated circuit applications has been a strong influence in the expansion of markets for ferroelectric ceramics. Ferroelectrics perform three major functions in circuits:1. They store energy with a high volume efficiency,2. They have very useful large changes in impedance with frequency, and3. They transduce between various energy forms and electrical signals.For many years commercial ferroelectric ceramics have been dominated by the barium titanate and lead zirconate titanate (PZT) systems. A tremendous research effort has been dedicated to these systems with very interesting studies still progressing on basic understanding, reproducibility, and modifications to utilize inexpensive electrodes. Processing studies are also seeking to reduce the size of devices and develop new transducing and sensing applications. The need to reduce cost and to fulfill specific applications is creating demands for new materials. Much of this effort has centered on lead-based systems referred to as relaxor ferroelectrics.The areas of application of ferroelectrics are narrowed in this review by eliminating the interfacial (grain-grain boundary) devices and electro-optic applications discussed in “Electronic Ceramic Thin Films” by Bruce Tuttle in this issue. Also, this article can only cover a small fraction of the information indicated by the title.

Growth and ferroelectric properties of tungsten bronze Ba 2− xSr xK 1− yNa yNb 5O 15 (BSKNN) single crystals

The undoped and Ce-doped ferroelectric tungsten bronze crystals, specifically Ba 1.5Sr 0.5K 0.75Na 0.25Nb 5O 15 (BSKNN-1) and Ba 0.5Sr 1.5K 0.5Na 0.5Nb 5O 15 (BSKNN-2), have been grown in optical quality using the Czochralski technique. Although both of these crystals are tetragonal with point group 4mm, their growth habit along the [001] direction differs: BSKNN-1 crystals grow in a square shape with four well-defined facets, while BSKNN-2 crystals have an octahedral growth habit with eight well-defined facets. The longitudinal dielectric (ϵ 11) and linear electro-optic ( r 51) constants show strong enhancement when expanding from BSKNN-1 and BSKNN-2 crystals, indicating that the latter could be of major interest for electro-optic, photorefractive and pyroelectric applications.

Development of microcomputer-aided pyroelectric thermal imaging system and application to pain management.

The paper presents a microcomputer-aided pyroelectric thermal imaging system developed for medical use. The processing procedures of this system can be divided into two stages: data acquisition and noise reduction. In the first stage, the video signal produced by the pyroelectric vidicon camera is digitised in synchronism with a chopper. In the second stage, averaging, immage-difference processing and local smoothing are applied to the obtained digital image. As a result, temperature resolution of less than 0·5°C was achieved on a four-bit digital image. The system was applied to pain management, and demonstrated a good performance in the evaluation of effects of nerve-block operations.

A trough for the fabrication of non-centrosymmetric Langmuir-Blodgett films

A method is described for the fabrication of non-centrosymmetric multilayer Langmuir-Blodgett (LB) films which are of interest for potential pyroelectric, piezoelectric and non-linear optical device applications. The substrate assembly is attached to a motorized device which is capable of both vertical and horizontal motion. Leaf springs, positioned in a barrier separating two spread monolayers (A and B), prevent the monolayers from mixing whilst allowing easy horizontal transfer of the immersed substrate between trough compartments with the substrate support rod passing between the springs. This mechanism enables the substrate to be cycled through A and B in an arbitrary sequence, and (i) minimizes the risk of unwanted cross-contamination of A and B (quantified using a fluorescent dye), (ii) maintains conventional vertical motion of the substrate through the spread monolayers and (iii) allows the rapid build-up of multilayer films, the rate in general being limited by the slower of the two monolayer deposition speeds. Flow of spread monolayers has been visualized for the new trough during the deposition of multilayer LB films, and the results are correlated with film morphologies observed using an optical birefringence technique; implications for film growth are discussed. Non-centrosymmetric alternating layer structures have been fabricated and, as expected, these films exhibited pyroelectric behaviour.

Ferro-Electric Materials: Trends & Applications

There has been a rapid progress in the field of ferro-electric materials and devices at all levels in research, development, production, discovering of new materials and development of new technologies. Although a large number of ferro-electric materials have been discovered, many of them are only of academic interest, whereas some have found innumerable applications as good transducer materials in piezo-electric, pyro-electric, and electro-optic applications. A review of such materials which are quite promising for device applications is presented in this article. In optical communication and office automation, there is an increasing demand for electrically-controlled component able to modulate or switch light. This function can be realized by using electro-optical effects in ferro-electric glass ceramics. They have good transparencies in the visible spectrum and near infra-red. Some of these materials are suitable for SAW devices, also. Pyro-electric materials find applications in point detectors and thermal imaging. Permanent piezo-electricity has been found in synthetic polymers and electrets which finds immense applications in underwater transducers. Inorganic fluorides with a general formula A5M3O9F5 form a new ferro-electric-ferro-elastic family. A2B2O7 type layer-structured crystals have high Curie points and also large piezo-electric and electro-optic constants. Semiconducting ferro-electrics such as SbSI are of interest because of the influence of carriers on ferro-electric properties. Many special purpose dielectrics e.g. high voltage, high temperature, low firing, microwave ceramics have been discussed.Relaxor ferro-electrics which have small thermal expansion, small electrostrictive co-efficients but very large permittivity, excel perovskite ferro-electrics such as PZT and barium titanate based ceramics. Relaxor ferro-electrics have the capability of producing enormous electrostriction, hence find applications in displacement transducers. Piezo-electric composites such as PZT/resin, PZT powder/rubber, Coral structured PZT/silicon rubber and the others have been developed which find growing applications as low density compliant flexible piezo-electric transducers.

Review of recent work on pyroelectric applications

Abstract Applications of pyroelectric devices in infrared detection, thermal imaging, and a broad spectrum of other areas are described.