Showing papers on "Pyroelectricity published in 1987"
TL;DR: In this article, the physics of pyroelectric infra red detectors as it applies to the selection of detector materials is briefly reviewed and the properties of a number of more commonly used materials are compared.
Abstract: The physics of pyroelectric infra red detectors as it applies to the selection of detector materials is briefly reviewed and the properties of a number of the more commonly used materials are compared. The use of ferroelectrics in the region of the Curie temperature as dielectric bolometers with an applied bias field is assessed and the properties of barium strontium titanate and lead magnesium niobate for use in this mode are reported and their potential compared with the conventional pyroelectrics.
189 citations
TL;DR: In this article, high sensitive pyroelectric infrared sensors were fabricated by using the La-modified PbTiO3 (PLT) thin films with high figures of merit for infrared detector were studied on the thin films.
Abstract: Highly c‐axis oriented La‐modified PbTiO3 (PLT) thin films were deposited on (100) oriented Pt thin film or (100) cleaved MgO single crystals by rf‐magnetron sputtering. Figures of merit for infrared detector were studied on the PLT thin films. It was found that a composition Pb1−xLaxTi1−x/4O3 where x=0.10 (PL10) was the most suitable for the infrared detector. The films have the advantage of having pyroelectric effect and polarization with the same direction even without a poling treatment. The films have high figures of merit Fv(=γ/cver) of 0.83×10−10 (C cm/J) and Fm(=γ/cv(er tan δ)1/2) of 1.2×10−8 (C cm/J) because of relative low‐dielectric constant er of 200 and high‐pyroelectric coefficient γ of 5.3×10−8 C/cm2 K. Both the Fv and the Fm of the films are 3 times as large as those of PbTiO3 ceramics. High sensitive pyroelectric infrared sensors were fabricated by using the PL10 films. The thickness of the films is 2 μm, and the electrodes were vacuum evaporated Ni‐Cr of approximate area 7×10−4 cm2. The ...
134 citations
TL;DR: In this paper, the pyroelectric properties of epitaxial PZT films were investigated using X-ray and RHEED measurements, and they were determined to have 45 and 3×10-9 C/cm2 K at room temperature, respectively.
Abstract: [111]-oriented PZT films have been successfully grown with good epitaxy onto epitaxial platinum film substrates by the rf-magnetron sputtering method using Pb enriched PZT(90/10) targets. The sputtering conditions for growing epitaxial films were investigated. Crystallographic identifications of the films were made by the X-ray and RHEED measurements. Dielectric, ferroelectric and pyroelectric properties of these films were measured. Pyroelectric coefficients at room temperature were determined as 45 and 3×10-9 C/cm2 K for epitaxial PZT films with poling and without poling treatments, respectively. Epitaxial PZT films sputtered on Pt/sapphire possess desirable properties for potential applications to pyroelectric devices.
106 citations
TL;DR: In this article, the linear response of polarization to a uniform change in temperature, in its gradient (thermal polarization effect), in macroscopic deformation and in its gradients (flexoelectric effect) was analyzed.
Abstract: An analysis has been made of the linear response of polarization to a uniform change in temperature, in its gradient (thermal polarization effect), in macroscopic deformation and in its gradient (flexoelectric effect). It has been shown how the use of some definitions of polarization widespread in the literature can lead to essentially incorrect results in the analysis of piezo- and flexoelectric effects in the field of elastic deformations of an acoustic wave. It has also been shown that in calculating the above responses in the case of a spatially uniform disturbance in a sample of finite size two classes of contributions arise: 1) contributions depending on the microscopic properties of the lattice, and 2) contributions depending only on changes in the distortion tensor accompanying the response, and on multipole moments of the charge distribution of the whole unperturbed crystal. In this connection it was established that the former contributions are bulk effects while the latter ones are surface or false contributions (which are not manifested in the generally accepted experimental arrangements for measurements). The special features of the manifestation of the flexoelectric and thermal polarization effects are discussed in detail.
54 citations
TL;DR: In this article, the pyroelectric activity in the alternating-layer Langmuir-Blodgett (LB) assemblies has been assessed and correlated with their structures determined using Fourier transform IR (FTIR) spectroscopy.
44 citations
TL;DR: In this paper, the dielectric, piezoelectric and pyroelectric properties of tungsten bronze single crystals in the Pb1-xBaxNb2O6 system were determined.
Abstract: Tungsten bronze single crystals in the Pb1-xBaxNb2O6 system were grown from a melt using the Czochralski technique. The dielectric, piezoelectric and pyroelectric properties were determined. The dielectric constant Ka and piezoelectric coefficient d15 showed a strong enhancement upon approaching the tetragonal: orthorhombic morphotropic phase boundary as predicted by thermodynamic phenomenology. It is clear that crystals with a composition in the tetragonal phase field near this boundary will be of major interest for various piezoelectric device applications.
38 citations
Journal Article•
36 citations
TL;DR: In this paper, the laser intensity modulation method (LIMM) was modified in order that it could be used with ferroelectric ceramic samples having thicknesses of the order of 1 mm rather than the tens of micrometers found in conventional polymer films.
Abstract: A new method for measuring the spatial distribution of combined polarization and space charge in poled polymer electrets was recently developed. The technique, called the Laser Intensity Modulation Method (LIMM), was modified in the present study in order that it could be used with ferroelectric ceramic samples having thicknesses of the order of 1 mm rather than the tens of micrometers found in conventional polymer films. PZT ceramics with a high Sn content and with compositions close to the Zr phase boundary were studied. The effects of poling conditions on polarization and space charge distributions in the two ferroelectric phases were examined. The polarization distributions were highly nonuniform, being flat in the central regions and diminishing strongly in the regions close to the electrodes. This was true even in samples poled to saturation. Large amounts of space charge were observed in the central regions. Pyroelectric coefficients and spontaneous polarizations were also measured.
24 citations
TL;DR: The pyroelectric properties of DMACA single crystals have been measured in the range 135-293 K, revealing the existence of ferroelectric second order phase transition at Tc = 243 K.
21 citations
Patent•
3M1
TL;DR: A pyroelectric and isotropic piezoelectric polymeric polymeric film was described in this paper, which was formed from a blend of polyvinylidene fluoride and at least one polymer miscible therewith.
Abstract: A pyroelectric and isotropic piezoelectric polymeric film, the film being formed from a blend of polyvinylidene fluoride and at least one polymer miscible therewith, and prepared by forming the film, heating it to a temperature sufficient to render the film substantially amorphous, cooling at a rate and to a temperature sufficient to prevent crystallization, and polarizing the film to render same β-crystalline and pyroelectric and isotropically piezoelectric.
TL;DR: In this paper, the dielectric and the pyroelectric behavior and the nature of absorption and steady state of currents have been studied for a ceramic and a polymer-ceramic composite over wide ranges of frequency and poling field and a limited range of temperature.
Abstract: The dielectric and the pyroelectric behaviour and the nature of absorption and steady state of currents have been studied for a ceramic and a polymer-ceramic composite over wide ranges of frequency and poling field and a limited range of temperature. The relative permittivity and the pyroelectric coefficient of the composite are observed to be significantly higher than those of the polymer. The dielectric loss processes of the composite are observed to be dominated by those of the polymer whereas the ceramic phase contributes significantly to the steady state electrical conduction which is observed to be of ionic nature.
TL;DR: In this article, it was shown that the threshold for spontaneous ferroelectric microdomain reversal is within the bounds of the dc and rf fields necessary for this phenomenon to occur.
Abstract: Spontaneous ferroelectric domain reversal in lithium niobate has been observed on a microscopic scale (∼0.1 μm) on standard surface acoustic wave (SAW) 128°‐rotated Y‐cut material due to pyroelectricity. Scanning electron micrographs are shown which clearly indicate the crystallographic shape of these reversed domains. Effective steps have been taken to eliminate this cause of domain reversal, and experiments were performed to measure the dc and rf fields necessary for this phenomenon to occur. In this paper we present our observation of spontaneous polarization reversal at room temperature. We discuss domain reversal in light of studies into the stress induced on the substrate by thin metal films. Theory behind this spontaneous polarization reversal and the threshold electric fields required to cause this reversal in the presence of thin metal film stresses is presented. From this discussion it is made clear that the threshold for ferroelectric microdomain reversal is within the bounds of the fields crea...
TL;DR: In this article, the pyroelectric properties of a hot-pressed PLZT (8/40/60) were investigated in some detail to evaluate its potential as a prospective pyro-electric infrared detector material.
TL;DR: In this paper, a series of twelve Li1−x Ta1−3x Ti4xO3 solid solution ceramics was sintered following the low-temperature metal alkoxide routes.
Abstract: A series of twelve Li1−x Ta1−3x Ti4xO3 solid solution ceramics was sintered following the low-temperature metal alkoxide routes. Measurements of dielectric constants, dielectric losses, and heat capacities as functions of temperature and frequency are presented. The Curie temperature (Tc) in comparison to LiTaO3 was reduced from 620°C to about 358°C in the Li0.91 Ta0.73 Ti0.36O3 ceramics. The heat capacity data showed no dependence on the bulk density or grain size. Also the mechanical properties of the undoped crystals appear to stay undisturbed. On the other hand, an apparently abnormal dependence of the Curie temperature on density was found. Heat capacity and dielectric loss decreased while the dielectric constant increased with the addition of Ti+4 doping in the LiTaO3 structure. Overall, a good detector performance might indeed be obtained from these ceramic materials if they can be poled reproducibly.
TL;DR: In this paper, the complete dielectric, piezoelectric and electrooptic tensors have been determined for monoclinic nitrilotriacetic acid, N(CH2COOH)3, NTA, and orthorhombic isotypic X2Zr[N(CH 2COO)3]2 · 2 H2O (X = K, Rb, Cs) from aqueous solutions.
Abstract: Large single crystals of monoclinic nitrilotriacetic acid, N(CH2COOH)3, NTA, and of orthorhombic isotypic X2Zr[N(CH2COO)3]2 · 2 H2O (X = K, Rb, Cs) have been grown from aqueous solutions. They possess optical quality and have dimensions up to 10 mm and larger. The complete dielectric, piezoelectric and electrooptic tensors have been determined. The maximum longitudinal and transversal piezoelectric effects exceed those of α-quartz by roughly a factor 11. The pyroelectric effects in NTA and in the X2Zr-salts (X = K, Rb, Cs) are by about a factor 3 larger than that in tourmaline, whereas the maximum electrooptic effects amount only to about half of that in KH2PO4. Qualitative measurements of the nonlinear optical properties by the aid of a SHG powder test and on single crystals revealed effects comparable with those observed in LiIO3. Phase matching is possible in these compounds. Replacing X by NH4 or Tl also acentric crystals are obtained with strong polar properties.
TL;DR: In this article, the authors proposed a type II pyroelectric detector for linear 1-D detectors with as many as 1000 elements, where the signal does not arise from surface bound-charges since the electrodes are parallel to the spontaneous polarization direction.
TL;DR: In this article, the pyroelectric coefficient of rhombohedral ferroelectric Pb(Zr1-xTix)O3 ceramics with x=0.04 to 0.12 was investigated.
Abstract: PZT ceramics with compositions close to PbZrO3 possess many desirable properties for potential applications in pyroelectric and piezoelectric devices. Sintering of rhombohedral ferroelectric Pb(Zr1-xTix)O3 ceramics with x=0.04 to 0.3 and their dielectric, ferroelectric and pyroelectric properties were investigated. The pyroelectric coefficient of the ceramics with x=0.05 was determined as 53×10-9 C/cm2K at room temperature. However, the thermal hysteresis of pyroelectric coefficient was clearly observed. On the other hand, experimental evidence for the second order nature of the higher phase transition from FR(HT) to cubic and the lower phase transition from FR(LT) to FR(HT) occurred at x of around 0.12 in the PZT ceramic system was given in this paper.
TL;DR: In this paper, thermal current analysis (TCA) was used to simultaneously measure pyroelectric and relaxation currents in a number of commercial corona-poled PVdF films, over the temperature range 0-120 degrees C.
Abstract: Using the thermal current analysis (TCA) technique, pyroelectric and relaxation currents have been simultaneously measured in a number of commercial corona-poled PVdF films, over the temperature range 0-120 degrees C. A relaxation peak observed at approximately=55 degrees C is attributed to space charge residing at the crystal/amorphous boundaries of beta -crystallites, resulting in partial dipole cancellation. Annealing films at 60 degrees C removes these charges and produces an enhancement of about 10% in pyroelectricity (measured at 25 degrees C), which subsequently decays with a time constant of about 2 h at room temperature. A second relaxation peak is observed at about 80 degrees C and, although its origin is undetermined, pyroelectric measurements suggest that the underlying mechanism may also be responsible for about 10% of the pyroelectric activity possessed by a new sample.
TL;DR: The ferroelectric members of the KDP-family exhibit piezoelectricity in both the paraelectric and ferroid phases, and pyroelectricity in the ferroid phase.
Abstract: The ferroelectric members of the KDP-family exhibit piezoelectricity in both the paraelectric and ferroelectric phases, and pyroelectricity in the ferroelectric phase. The piezoelectric effect has been studied extensively, both fundamentally and for applications. Its anomalous behavior in the vicinity of the Curie point has been shown to be a direct consequence of the dielectric anomaly. The much-less examined pyroelectric effect has been used for determining spontaneous polarization and studying low-lying optic modes. Most of the piezoelectric data on the KDP-family available in the literature are discussed in this paper.
TL;DR: An electric polarization which contains spontaneous electric polarization and magnetoelectric polarization of magnetite was measured over a temperature range from 42 K to 60 K as mentioned in this paper, where the observed electric polarization is divided into two parts : one is due to rotation of magnetization and the other is independent of it.
Abstract: An electric polarization which contains spontaneous electric polarization and magnetoelectric polarization of magnetite was measured over a temperature range from 42 K to 60 K The observed electric polarization is divided into two parts : one is due to rotation of magnetization and the other is independent of it An anomalous behavior in temperature dependence was observed in both of these two parts at the same temperature of 6 K In earlier reports, anomalous behaviors in pyroelectric polarization and in magnetoelectric polarization were measured individually at this temperature Another anomaly was observed at about 45 K, which was interpreted as an effect due to the switching of the a axis to the b axis by the magnetic field A change caused by breaking of the mirror symmetry was not observed at about 10 K in the present measurements
TL;DR: In this article, the pyroelectric properties of poled solid solutions of lead-barium titanate and leadstrontium titanates have been investigated in the temperature range covering their transition points.
Abstract: Pyroelectric properties of poled solid solutions of lead-barium titanate and leadstrontium titanate have been investigated in the temperature range covering their transition points. The values of pyroelectric current and coefficients of (Pbx − Ba1 −x)TiO3 and (Pbx − Sr1 −x)TiO3(x = 0·8 − 0·5) show a sharp peak at the Curie temperature. It is observed that these values change with Ba or Sr concentration in the respective solid solutions.
TL;DR: In this article, the influence of dopants on the growth habits, crystal morphology pyroelectric properties and structure parameters of TGS crystals has been systematically investigated, and the effects of the domain structure of the seed crystal on the pyropelectric properties of the doped crystals have been studied.
TL;DR: In this paper, the classification of mechanisms of piezo-and pyroelectricity in polymers and recent developments in these fields with special emphasis on ferroelectric polymers are described.
Abstract: This review describes the classification of mechanisms of piezo-and pyroelectricity in polymers and recent developments in these fields with special emphasis on ferroelectric polymers.
TL;DR: In this article, the authors investigated pyroeffects, longitudinal and transverse with respect to the direction of preliminary polarization, in PbZrO3 crystal and detected Barkhausen pulses from the residual domains.
Abstract: Pyroeffects, longitudinal and transverse with respect to the direction of preliminary polarization, were investigated in PbZrO3 crystal. In the vicinity of the transient ferroelectric phase, Barkhausen pulses from the residual domains were detected. These pulses occur against the background of the continuous current component related to disappearance of the space charge polarization. Reasons for the diffusion of the phase transitions and also the nature of the residual current observed in the neighbourhood of the intermediate ferroelectric phase are discussed.
TL;DR: In this paper, the current thin film technology and possible opportunities for the developing Langmuir-Blodgett thin film deposition technique are reviewed with an emphasis on applications and possible applications of thin film.
Abstract: Oriented films possessing dipole moments have seen increasing use of their piezoelectric and pyroelectric properties in pressure, acoustic, thermal, and optical devices. The performance of these devices in many applications is enhanced by thin film technology. The current thin film technology and possible opportunities for the developing Langmuir-Blodgett thin film deposition technique are reviewed with an emphasis on applications.
TL;DR: In this article, a Philips X-ray diffractometer was used to obtain the crystal structure of Li ammonium sulphate (LiNH4SO4) and the temperature dependence of the unit cell parameters, such as dc resistivity, ac resistivity and dielectric constant, as well as the pyroelectric current, were obtained in a wide range of temperatures.
Abstract: Crystalline samples of lithium ammonium sulphate are prepared. The crystal structure of the crystals obtained is investigated by means of a Philips X-ray diffractometer yielding the following values for the unit cell parameters: a = 6.43 A, b = 5.24 A, and c = 5.02 A and α = β = γ = 90° indicating that LAS exists at room temperature in an orthorhombic phase. The temperature dependence of the dc resistivity Qac, ac resistivity Qac, dielectric constant ϵ′, and dielectric loss ϵ″, as well as that of the pyroelectric current are obtained in a wide range of temperatures covering all the structural changes occuring in LiNH4SO4. Two remarkable anomalies at 18 and 185 °C are detected. The observed anomaly of ϵ′ at 185 °C is found to be much smaller than that observed at 18 °C. Good accordance is observed between the temperature dependence of both Q and ϵ′ as well as the temperature dependence of the pyroelectric current. The ferroelectric behaviour of the samples in the temperature range 18 to 185 °C is correlated with the deformation of sulphate ions in addition to the vibrational motion of the SO and NH4+ ions. The role of the addition of the complex ion NH+ to the LiSO4 crystals is considered by studying the effect of the change of the value of the parameter x for the complex crystal Li1–xNHxSO4 on the mechanism of the phase transition and the transition temperature Tc.
Patent•
20 Mar 1987
TL;DR: In this article, a pyroelectric film composed of an oriented polarization body of a vinylidene fluoride copolymer having a crystallization degree of 60% or more and specific inductive capacity of 10 or less in a low frequency region of 0.1W10Hz at 25°C.
Abstract: PURPOSE: To enhance the sensitivity and heat resistance of a sensor, by incorporating a pyroelectric film composed of an oriented polarization body of a vinyliden fluoride copolymer having a crystallization degree of 60% or more and specific inductive capacity of 10 or less in a low frequency region of 0.1W10Hz at 25°C. CONSTITUTION: This sensor is constituted by arranging a pyroelectric film having output taking-out electrodes 3, 4 arranged to both surface thereof toward an infrared ray incident window 1a and the pyroelectric film is composed of an oriented polarization body of a vinylidene fluoride copolymer having a crystallization of 60% or more and specific inductivity of 10 or less in a low frequency region of 0.1W10Hz at 25°C. For example, the infrared rays incident through the fanwise opening part of a chopper 10 usually arranged to the front surface of the incident window 1a and rotating by low frequency of about 0.1W10Hz give the temp. change corresponding to the incident quantity thereof to an element 5 and the electric fields generated on both surfaces of the element 5 corresponding to the temp. change of polarization are converted to impedance by FET 7 to be taken out from a source as output. By this constitution, the sensitivity and heat resistance of the sensor can be enhanced. COPYRIGHT: (C)1988,JPO&Japio
TL;DR: In this paper, the pyroelectric properties of benzene derivatives, 1-Cl-3-NO2-C6H4 and 1-CN-4-Br-C 6H4, were investigated in the temperature range 100 ≦ T/K ≦ decomposition temperature.
Abstract: The pyroelectric properties of the benzene derivatives, 1-Cl-3-NO2-C6H4, 1-CN-4-NO2-C6H4, and 1-CN-4-Br-C6H4, were investigated in the temperature range 100 ≦ T/K ≦ decomposition temperature. Dielectric measurements of single crystals of these compounds were performed. By use of a semiempirical quantum chemical model, including a point charge model of the solid matrix, the charge distributions in the molecules are calculated. With the therefrom resulting dipole moment and properties of a polar dielectric the change of the pyroelectric coefficient p with temperature is calculated. The experiments and calculations are discussed in connection with the known crystal structures of the substances.