Search

The characterization of pyroelectric materials is essential for the design of pyroelectric-based devices. Pyroelectric current measurement is the commonly employed method, but can be complex and requires surface electrodes. Here, we present noncontact electrostatic voltmeter measurements as a simple but highly accurate alternative, by assessing thermally-induced pyroelectric surface potential variations. We introduce a refined model that relates the surface potential variations to both the pyroelectric coefficient and the characteristic figure of merit (FOM) and test the model with square-shaped samples made from PVDF, LiNbO3 and LiTaO3. The characteristic pyroelectric coefficient for PVDF, LiNbO3 and LiTaO3 was found to be 33.4, 59.9 and 208.4 [Formula: see text]C m[Formula: see text]K[Formula: see text], respectively. These values are in perfect agreement with literature values, and they differ by less than 2.5% from values that we have obtained with standard pyroelectric current measurements for comparison.

Pyroelectric materials are important functional materials that can generate an electrical response upon a temperature change. Among the many different types of pyroelectric materials, lead-based materials are the most widely-used traditional pyroelectric material and they will soon be banned due to their high toxicity. Therefore, in the past decade, extensive studies have been conducted to search for high performance lead-free pyroelectric materials. Recent experimental efforts have led to significant advances in lead-free pyroelectrics in different forms. This has further motivated their application from a traditional sensing function to a future energy-related prospect. This article provides a comprehensive review on the up-to-date advances in lead-free pyroelectrics, including single crystals, ceramics, inorganic films, polymers and composites. Moreover, the recent rise in energy harvesting and the electrocaloric effect as well as the potential future development of pyroelectric applications will be presented.

X-rays are a type of electromagnetic energy which widely used in different areas. Since their discovery, x-rays have been used, especially for medical imaging applications. On the other hand, new efficient x-ray generation methods have still been under investigation. Although new imaging modalities arose, xrays have never lost their popularity in many applications like computed tomography and dental imaging. Among these new methods, x-ray generation using pyroelectric crystal materials is one of the promising technologies. Pyroelectric crystals generate an electric field when a temperature change occurs and are affected by various parameters like how many times (count) the crystal’s temperature changed in a second. Hence, this new technology needs more research. In this study, we investigated the relationship between the count number and x-rays’ energy level of pyroelectric materials using linear regression analysis. We used a commercial software package, which is called the Statistical Package for the Social Sciences (SPSS), for this purpose. As a result, we achieved a good fit value of R2 = 0.91.

cited By 2; International audience; We deal with the thermal energy which is one of the ambient energy sources surely exploitable, but it has not been much interest as the mechanical energy. In this paper, our aim is to use thermal energy and show that it's an important source for producing the electrical energy through pyroelectric effect which is the property of some dielectric materials to show a spontaneous electrical polarization versus temperature. In this context, we present a concept to harvest a thermal energy using infrared rays and pyroelectric effect. The pyroelectric material used in this work can generate an electrical voltage when it subjected to a temperature change which will be ensured by the use of infrared lamp. Our experimental results show that the electrical voltage, current and harvested power increased significantly when increasing the area of the pyroelectric element. The experimental results show also that with this simple concept we harvested a heavy amount value of power which will certainly be useful in an extensive range of applications, including sensors and infrared detection. These results shed light on the thermoelectric energy conversion by Ceramic lead zirconate titanate (PZT) buzzer having the pyroelectric property. © 2016 Elsevier B.V. All rights reserved.

Pyroelectricity is mainly affected by the structure of materials. To explore the influence of the structure on pyroelectricity, a new type of pyroelectric materials with structure of tourmaline consisting of Li9Mg3[PO4]4F3, Ba3Sr4(BO3)3F5 and tourmaline have been systematically studied in this work. Based on the comparison results of the pyroelectric coefficient of Li9Mg3[PO4]4F3 and Ba3Sr4(BO3)3F5 after heating and the variations of electric dipole moment, it suggests the tetrahedron is less stable than trigon, and is easily to cause the distortion and deformation of structure, which leads to the great enhancement of pyroelectricity. Additionally, it can find that the tetrahedron has the most contribution to the pyroelectricity by comparing the pyroelectric coefficient and total electric dipole moment of Li9Mg3[PO4]4F3, Ba3Sr4(BO3)3F5 and tourmaline which have different polyhedrons.

As one important subclass of piezoelectric materials, pyroelectric materials have caused increasing attention owing to the unique pyroelectric effect induced by spontaneous polarization, showing broad promising application prospects due to various electrical responses induced by time-dependent temperature variation. This review systematically introduces the pyroelectric effect and evaluation of pyroelectric materials and follows by analyzing and concluding the novel properties corresponding to four kinds of main pyroelectric materials. The emphasis of this review focuses on several significant and practical applications of pyroelectric materials in thermal energy harvesting from the external environment, pyroelectric sensing, and imaging, even some electrochemical applications including hydrogen generation, wastewater treatment, sterilization, and disinfection. Finally, the development direction of pyroelectric materials, potential challenges and opportunities in the future are all discussed and proposed. Through systematical conclusion and analysis of the latest research progress in the recent two decades, this review may provide significant guide and inspiration in the development of pyroelectric materials.

The field of waste thermal energy harvesting has experienced significant growth over the past few years. This paper presents an experimental study on thermal radiation to electrical energy conversion using pyroelectric material (PbZrxTi1-xO3 (PZT-5H)). Pyroelectric material was exposed to UV lamp with a constant frequency of 0.5 Hz and another surface of sample was continuously cooled via natural air fan (for generation continuous temporal gradient in material). Maximum value of stored energy was 1.75 µJ across 100 µF without load resistance. Maximum power output was found to be 0.76 µW across load resistance of 3 MΩ and 10 µF.

The purpose of this work is to demonstrate a new simple stand-alone method of characterizing the impedance of a pyroelectric cell. This method utilizes a pyroelectric single pole low-pass filter technique. Utilizing the properties of a pyroelectric single pole low-pass filter technique, a known input voltage is applied and using simple equations, capacitance Cp and resistance Rp at a frequency range of 1 mHz to 1 Hz can be calculated. For verification purposes, an LCR meter and an impedance analyzer were exploited at 10 and 100 Hz, respectively. Results showed that Rp values for two materials, lead zirconate titanate-5A and polyvinylidene difluoride, were within 8%, and Cp values were within 7.5%. In addition, to verify the importance of the impedance values in energy harvesting applications, output power was measured with varying impedance values. The optimal load resistances for polyvinylidene difluoride and lead zirconate titanate-5A were consistent with the measured pyroelectric impedance at the particular heat range with 10.9% and 1.4%, respectively. The pyroelectric single pole low-pass filter method presented here demonstrates that for pyroelectric materials the impedance depends on two major factors: (1) average working temperature and (2) the heating rate. Neglecting these two factors can result in inefficient and unpredictable behavior of pyroelectric materials when used in energy harvesting applications.

Pyroelectric materials have been utilized in several ways to harvest waste thermal energy using pyroelectric effect. One basic requirement for pyroelectric materials to work is the presence of temporal temperature variations, i.e., time gradients of temperatures. For practical thermal energy harvesting applications using pyroelectric effect, Olsen cycle has the highest adoption rate amongst various cycles for it has the highest energy density. In accordance to theoretical calculation, an increase in the energy density can be made possible through broadening the electric field span, in turn necessitates sufficiently high dielectric breakdown strength that the pyroelectric materials should have. This chapter serves to offer an overview on progress in pyroelectric effect and pyroelectric materials that have been employed to harvest waste thermal energies.

Termal görüntüleme cihazlarının, askeri, endüstri ve uzay araştırmaları gibi geniş uygulama alanlarından dolayı, sıcaklığa bağlı polarize olan pyroelektrik maddeleri üzerindeki çalışmalar, araştırmacıların ilgisini çekmektedir. Bu maklede, pyroelektrik olayın, pyroelektrik maddelerin ve bu maddelere ait bazı uygulamaların genel bir değerlendirilmesi verilecektir, The wide range of applications of thermal imaging devices existing in military, industrial and space fields attract researchers to study pyroelectric materials which exhibit a temperature-dependent spontaneous polarisation. A brief review of pyroelectricity, pyroelectric materials and some commercial applications of these materials we will be given in this paper

This review covers energy harvesting technologies associated with pyroelectric materials and systems. Such materials have the potential to generate electrical power from thermal fluctuations and is a less well explored form of thermal energy harvesting than thermoelectric systems. The pyroelectric effect and potential thermal and electric field cycles for energy harvesting are explored. Materials of interest are discussed and pyroelectric architectures and systems that can be employed to improve device performance, such as frequency and power level, are described. In addition to the solid materials employed, the appropriate pyroelectric harvesting circuits to condition and store the electrical power are discussed.

According to the actual road conditions, the representative temperature, ultraviolet light intensity, and exhaust concentration were selected as the test environment. A study of the law of vehicle exhaust decomposition under different levels was conducted, and the phenomenon of temperature-light equivalence during a catalytic process was proposed. The decomposition products of exhaust gas from nanotitanium dioxide were detected by chemical analysis, and relevant information was obtained through the reaction process. Besides this, the effects of a piezoelectric system and pyroelectric materials on the catalytic efficiency of nanotitanium dioxide were also investigated. Meanwhile, the influence of pyroelectric materials on the catalytic activity of nanotitanium dioxide in different environments was also evaluated. With the increase of load, loading frequency, and temperature, the effect of tourmaline powder on the decomposition of vehicle exhaust gas is improved, and the influence of load and temperature was more obvious than that of the frequency.

Harvesting energy from such renewable energy resources as solar, vibration, thermal and magnetism in microelectromechanical systems has gained much attention from researchers in recent decades. From among these resources using piezoelectrics and pyroelectrics due to their ease in the design and implementation has attracted more attention. In this paper, a new harvesting technique has been considered, which uses piezoelectrics and pyroelectrics simultaneously. The concept of method and theoretical analysis for hybrid energy harvesting method is presented and then by exerting vibration and heat forces, the average harvested power is determined. This investigation has been done by considering PZT and PMN-0.25PT ceramics as smart elements. Different strategies for switching have been considered in synchronized switch harvesting method and then the best switching between these three strategies—switching on voltage, mechanical displacement or temperature amplitude—is introduced. In each condition, the positive influence of hybrid method has been as compared with piezogenerators for both smart elements. The effect of four important parameters—temperature amplitude, vibration amplitude, inversion coefficient, and equivalent load resistance—is examined. The most effective switching method and material are proposed in the final part of the paper.

Pyroelectric energy harvesting is one of the feasible ways to harvest waste heat from human body. Heat is constantly lost from human body to maintain a constant temperature through a process known as thermoregulation. The maximum heat lost from the human body to the environment occurs through the skin. The heat loss varies throughout the human body, but, the most at the feet, the palms, and the exterior back which are the optimal areas for pyroelectric energy harvesting. In this paper, we investigate the feasibility of harvesting energy from the human body to power portable electronic devices such as computer mice. Current computer mice use either batteries or USB ports for power and run continuously, consuming significant amount of power. We present the design of a pyroelectric computer mouse, that uses the heat of the user's palm to power or supplement the energy demand of the mouse. Important parameters such as the heat generation rate of users, the design of the pyroelectric system, and the optimal op...

The phenomenon of polarization fatigue in ferroelectric materials is defined and the effect of this phenomenon on harvested energy using these materials has been studied. In order to illustrate this effect, the harvested energy using PZN-4.5PT single crystal was compared in two cases of fatigued and nonfatigued samples. The results have been calculated between two temperatures of 100 and 130°C using Ericsson thermodynamic cycle.

An attempt has been made to provide the ranking of piezoelectric and pyroelectric materials using technique for order preference by similarity to ideal solution (TOPSIS) method. To calculate weight (priority) for all the attributes (properties) understudy, entropy method is used. Interestingly my results suggest that dielectric constant is a key parameter (after d33 coefficient) which governs selection of piezoelectric materials. PLZT (8/65/35) and LiTaO3 ceramics place on first rank among studied piezoelectric and pyroelectric materials, respectively. These materials are classified using hierarchical clustering which shows similarities between the materials irrespective to their ranking obtained using TOPSIS method.

This paper is concerned with directly converting waste heat into electricity using pyroelectric materials. A prototypical pyroelectric converter is simulated by solving the two-dimensional mass, momentum, and energy equations using finite element methods. The pumping power and the electrical power generated are estimated from the computed pressure, temperature, and velocity. The results show that the energy efficiency increases as the density and specific heat of the working fluid and of the pyroelectric material decrease. Moreover, the power density increases as the density and specific heat of the working fluid increase and those of the pyroelectric material decrease. One can reasonably achieve an energy efficiency of 40% of the Carnot efficiency and a power density of 24 W/L of pyroelectric materials.

A method of continuously harvesting energy from pyroelectric materials is demonstrated using an innovative cyclic heating scheme. In traditional pyroelectric energy harvesting methods, static heating sources are used, and most of the available energy has to be harvested at once. A cyclic heating system is developed such that the temperature varies between hot and cold regions. Although the energy harvested during each period of the heating cycle is small, the accumulated total energy over time may exceed traditional methods. Three materials are studied: a commonly available soft lead zirconate titanate (PZT), a pre-stressed PZT composite, and single-crystal PMN-30PT. Radiation heating and natural cooling are used such that, at smaller cyclic frequencies, the temporal rate of change in temperature is large enough to produce high power densities. The maximum power density of 8.64 μW/cm3 is generated with a PMN-30PT single crystal at an angular velocity of 0.64 rad/s with a rate of 8.5°C/s. The pre-stressed PZT composite generated a power density of 6.31 μW/cm(3), which is 40% larger than the density of 4.48 μW/cm3 obtained from standard PZT.

Recently, scientists discovered that relaxor-based ferroelectric single crystals, such as (1-x)Pb(Mg1/3Nb2/3)O3 -xPbTiO3 (PMN-xPT, or PMNT) single crystals, exhibit extra-high pyroelectric responses. They are promising candidates for optical power detectors in broad bandwidth at ultraviolet, visible and infrared wavelength.To fabricate high performance infrared detectors with relaxor-based single crystals, the related readout circuit was investigated to increase signal-to-noise ratio, and 8×1 CMOS readout circuit is fabricated to gain very weak current, which provides a solution for uncooled large focal plane arrays devices based on relaxor-based single crystals.

The development of low-cost, uncooled (room temperature operation) thermal detector arrays has been accelerating in recent years and now commercial products are becoming widely available. As costs come down and volumes rise, these devices are entering the consumer marketplace, providing everything from sophisticated security and people-monitoring devices to hand-held thermal imagers for preventative maintenance and building inspection. Two technologies have established significant market shares in uncooled thermal detector array products. These are resistive microbolometers and pyroelectric ceramics. To address the true mass market, the pyroelectric arrays offer significant cost advantage. In this paper, recent developments in a variety of products based on pyroelectric ceramic arrays are described and their performance and applicability are compared and contrasted with competing technologies. This includes the use of low-element-count arrays for applications in people counting and queue measurement, and the drive for cost-effective imaging arrays for mass-market thermal imaging. The technical challenges in materials production, device development, and low-cost manufacture are reviewed and future opportunities and challenges are outlined.

The characteristics of a new pyroelectric sensor that measures acceleration are presented. This accelerometer is based on the heat convective fluxes modified by an applied acceleration. In order to present the performances of this new device, firstly, numerical simulations will be shown using computational fluid dynamic software. Secondly, experimental results will be presented for different measurement mode.

Properties of a new type of pyroelectric ceramic structure containing a layer of known porosity laminated between two dense layers, to form a functionally gradient material (FGM), are reported. The combination of theoretical models for pyroelectric, dielectric, and thermal properties gave a model for the pyroelectric voltage figure of merit (F v ) in good agreement with experiment, which had shown a 20% improvement for an introduced central layer porosity of 27%. Preliminary pyroelectric responsivity measurements on FGM infrared detectors indicated an even better improvement. It is postulated that this is due to the porous layer acting as a thermal barrier in the structure.

Modern CPUs generate considerable wasted heat due to increased power dissipation from high-performance computation. Lots of research effort has extensively focused on using thermoelectric generators (TEGs) to harvest CPU waste heat to increase overall system energy efficiency. To harvest waste heat using TEGs requires a significant temperature differential between the processor as a heat source and the heat spreader/heat sink, as well as a high heat flow. However, the heat-to-electricity conversion efficiency is typically limited to 15 to 20 percent, due to large heat conductivity, low Seebeck coefficient, and low figure of merit of TEGs. In addition, TEGs on a CPU could significantly increase CPU junction temperature compared to the baseline CPU temperature due to its high thermal resistance. Contrary to using TEGs to harvest waste heat from a fixed, spatial temperature differential, this paper presents an approach to harvest CPU waste heat using pyroelectric (PE) materials from the time-varying, temporal temperature differential that is common in current processors. PE materials can generate electricity when subjected to a temporal temperature gradient. The operation of PE materials is distinctly different from TEGs and they have the following advantages. First, the theoretical efficiency is up to 50% using thin films. Second, the overall optimization of PE material is easier than thermoelectric material, since the conversion ratio, the ratio of net harvested energy divided by the heat taken from the hot reservoir, of PE material is independent of the material properties, whereas that of TEG is highly dependent on material properties. Although PE material is also a long-researched energy harvesting material, it is less explored by researchers compared to TEG in the application domain of processor waste heat management. In this paper, we review current PE materials in terms of pyroelectric coefficient and thermal conductivity, and also investigate the harvested power generation from CPU waste heat in a modern computing system.

A simplified photopyroelectric (PPE) configuration that allows the simultaneous determination of the temperature dependent thermal and pyroelectric parameters of pyroelectric materials is described. The thermal parameters (thermal diffusivity, conductivity, effusivity and volumic specific heat) are obtained from the analysis of the phase of the complex photopyroelectric (PPE) signal generated from the pyroelectric sample itself and measured for two different modulation frequencies. The pyroelectric coefficient is obtained from the amplitude of the signal. Experimental results on thermal and pyroelectric parameters of LiTaO 3 single crystal in the 25°C-70°C temperature range are reported.

Thin-film electrocaloric and pyroelectric sources for electrothermal energy interconversion have recently emerged as viable means for primary and auxiliary solid-state cooling and power generation. Two significant advances have facilitated this development: (1) the formation of high-quality polymeric and ceramic thin films with figures of merit that project system-level performance as a large percentage of Carnot efficiency and (2) the ability of these newer materials to support larger electric fields, thereby permitting operation at higher voltages. This makes the power electronic architectures more favorable for thermal to electric energy interconversion. Current research targets to adequately address commercial device needs including reduction of parasitic losses, increases in mechanical robustness, and the ability to form nearly freestanding elements with thicknesses in the range of 1–10 μm. This article describes the current state-of-the-art materials, thermodynamic cycles, and device losses and points toward potential lines of research that would lead to substantially better figures of merit for electrothermal energy interconversion.

The photopyroelectric calorimetry, in the standard (back) configuration, is applied in order to measure the thermal parameters of some pyroelectric materials. It is demonstrated that the method is able to simultaneously measure the thermal diffusivity and effusivity of a pyroelectric material. The information is obtained via a frequency scan of the amplitude or the phase of the pyroelectric signal; the measurements need no calibration. A combined amplitude-phase procedure, at a single frequency, leads to the same results. In the mean time, if the thermal parameters of the pyroelectric sensor are known, one can get the thermal effusivity of a sample acting in the experimental cell as a substrate. Investigations and theoretical simulations were performed on a well known pyroelectric material, LiTaO3, with various liquid substrates.

A pyroelectric phenomenon is a manifestation of the temperature dependence of spontaneous polarization on certain solids, which can be either single-crystal or poly-crystalline aggregates. When the temperature of the material is slightly increased, the electrical polarization of the material changes, and voltage can be measured between certain faces of the pyroelectric sample. Conversely, if the temperature of the material is lowered by the same amount, the same magnitudes of polarization and voltage are found with the signs reversed. Thus, pyroelectric materials provide a means of producing infrared (IR) detectors that conveniently operate at room temperature. In this chapter, a number of fundamental aspects of pyroelectricity are described regarding its application in IR detection and energy harvesting. Pyroelectric materials form a subgroup of piezoelectrics, while ferroelectrics form a subgroup of pyroelectrics. Relationships between crystal structure and relevant properties are discussed along with important candidate materials and their applications.

Pyroelectrics form a very broad class of materials. Any material which has a crystal structure possessing a polar point symmetry—i.e. one which both lacks a centre of symmetry and has a unique axis of symmetry—will possess an intrinsic, or spontaneous, polarisation and show the pyroelectric effect. The pyroelectric effect is a change in that spontaneous polarisation caused by a change in temperature. It is manifested as the appearance of free charge at the surfaces of the material, or a flow of current in an external circuit connected to it. The effect is a simple one, but it has been used in a range of sensing devices, most notably uncooled pyroelectric infra-red (PIR) sensors, and has thus come to be of some engineering and economic significance, enabling a wide range of sensing systems, ranging from burglar alarms through FTIR spectroscopic instruments to thermal imagers.

Pyroelectric materials have been fabricated in bulk single crystals, ceramic (polycrystalline), films, and composite forms. This chapter briefly reviews and describes all of the major and relevant techniques for processing key materials.

Pyroelectric energy conversion offers a novel, direct energy-conversion technology by transforming time-dependent temperature directly into electricity. It makes use of the pyroelectric effect to create a flow of charge to or from the surface of a material as a result of heating or cooling. However, existing pyroelectric energy converter can only operate at low frequency due to relatively low heat transfer rate between the pyroelectric materials and the working fluid subjected to oscillatory fluid flow between hot and cold sources. On the other hand, energy transfer by thermal radiation between two semi-infinite solids can be enhanced by several orders of magnitude as the gap separating them reduces to subwavelength size thanks to interference and tunneling of electromagnetic waves across the gap. This paper proposes a novel way to harvest nanoscale radiation heat transfer for direct pyroelectric energy conversion of waste heat into electricity. A new device is investigated numerically by accurately modeling nanoscale radiation heat transfer between the pyroelectric materials and hot and cold surfaces. Performance of the pyroelectric converter is predicted at various frequencies. The result shows that rapid energy transfer and higher operating frequency can be achieved to increase efficiency and power density.

The photopyroelectric signal is analyzed in order to simultaneously obtain the thermal diffusivity and effusivity of pyroelectric materials. Two different experimental configurations are described and compared in terms of accuracy and sensitivity. The information is obtained via a frequency scan of the amplitude or the phase of the pyroelectric signal. The methods have been used for the measurement of thermophysical properties of a lead–titanate–zirconate ceramic sample.

A simplified photopyroelectric configuration that allows the determination of the temperature-dependent thermal parameters of pyroelectric materials is described. The procedure is based on a combination of phase and amplitude signal data obtained at a single frequency. Experimental results obtained on the thermal parameters of LiTaO3 single crystal are presented.

Literature data on the characteristics of different types of ferroelectric materials are reviewed together with the results of own studies. The emphasis is made on the performance of these materials in pyrovidicon targets.

An automated system for the pyroelectric imaging of polar substrates has been developed. The principle of operation, details of the optical and mechanical subsystems, and a description of the system hardware, interface, and software for data acquisition and display are given. The automation has made possible routine scans of high resolution and/or large areas of pyroelectric materials, such as LiNbO/sub 3/ and ZnO. Features of the system are highlighted by means of a pyroelectric imaging of proton-exchanged LiNbO/sub 3/, which is an important material for optical waveguides. >

Pyroelectric solar energy harvesting has been a prominent area of research for the past few years. This study is an attempt to compare different pyroelectric materials for harvesting solar energy. Seven different pyroelectric materials including (NH2CH2COOH)3H2SO4 (TGS), Sr0.5Ba0.5Nb2O6 (SBN), Ca0.2(Sr0.5Ba0.5)0.8Nb2O6 (CSBN), Pb(Zr0.5Ti0.5)O3 (PZT), polyvinylidene difluoride (PVDF), BaTiO3 and LiTaO3 were studied and compared using finite-element analysis. SBN was found to be the potential pyroelectric material with the maximum storage voltage of 11.47 V across an optimized load capacitance. SBN was subjected to further analysis, revealing an optimum power output of 4.9 μW at the optimized cycle frequency (0.040 Hz), a load resistance of 50 MΩ and a load capacitance of 4.7 μF, while the stored energy was found to be 576.87 μJ.

Correction for ‘Pyroelectric materials and devices for energy harvesting applications’ by C. R. Bowen et al., Energy Environ. Sci., 2014, 7, 3836–3856.

An understanding of the power that can be harvested from pyroelectric materials and its dependence on material properties, geometry and boundary condition is crucial to the design of energy harvesting devices using these materials. In this paper, simple analytical expressions are developed for ideal voltage, power and power densities as a function of pyroelectric constant, permittivity, surface area, thickness, temperature variation and rate of change for unclamped samples. Experiments are performed to specifically study the effect of geometry and are compared with theoretical predictions.Copyright © 2009 by ASME

An improved quantitative pyroelectric characterization system has been developed in an effort to more thoroughly investigate the dynamic pyroelectric response of selected materials at particular temperatures of interest, such as at transition, or to study electrical aging effects. Specifically, the system is capable of measuring pyroelectric current responsivity of a wide variety of materials ranging from ferroelectric ceramics to polymers at constant temperature utilizing a modulated heating source technique.' Effectiveness of this system was determined through measurements of lithium tantalate and lithium niobate samples of various geometries. The result of the study was a comprehensive evaluation of dynamic pyroelectric current responsivity of these samples with a particularly good signal-to-noise enhancement for evaluating high noise materials such as polymer gels which are extremely difficult to evaluate using other techniques. These measurements revealed a significant dependence of the pyro...

In this paper, a new theory allowed calculating the pyroelectric coefficient “p” using the diffusion of a thermal wave within materials having a pyroelectric effect. The demonstration is performed on materials composed by various percentages of a cycloaliphatic epoxy (CE) resin and of a flexibilizing comonomer (1,6-hexanediol diglycidyl ether — HDGE). By using an electric field measurement technique (the Thermal Step Method — TSM), the signal obtained on these materials (a current) presents an atypical form, which requires the modification of the theoretical model of the TSM. Indeed, the theory of the TSM technique has been initially developed for insulating materials with a high dielectric time constant. An adaptation of the technique is thus necessary to analyze the behavior of materials, which present a modification of their molecular structure during the application of the thermal wave. During a space charge characterization performed on these materials, we have observed an atypical shape for the thermal step currents. To help in the interpretation, the broadband dielectric spectroscopy and the Differential Scanning Calorimetry technique (DSC) were used to obtain additional information. Considering these results, a circuit containing a resistor and a capacitor in series has been used for modeling the materials. This equivalent circuit constitutes the beginning of the new theory, which is developed in this paper. The pyroelectric coefficient generated by the thermal step diffusion, due to the presence of a pyroelectric effect of these studied materials, has been calculated using the detailed model.

The results of the study of TGS group crystals, physical properties as well as characteristics of pyroelectric vidicons with the targets made of the crystals are presented.