Effective Pyroelectric Coefficients Research Articles

Design and characterization of a pyroelectric detector based on three-dimensional structured hafnium oxide thin films

Pyroelectric detectors are used for gas analysis and flame detection because of their fast response and excellent performance. Most pyroelectric devices are based on monocrystalline lithium tantalate or pyroelectric lead zirconate titanate thin films deposited on a silicon (Si) substrate. In comparison, recently discovered pyroelectric-doped hafnium oxide (HfO2) offers the possibility of manufacturing completely complementary metal-oxide-semiconductor (CMOS)-compatible devices on large Si wafers. This is a promising approach to simplifying mass production of the sensor element and realizing new sensor structures with a high performance. Si substrates were structured with trenches and filled with thin-doped HfO2 layers by atomic layer deposition to multiply the pyroelectric current responsivity. An effective pyroelectric coefficient of up to 1300 μC / m2 / K was measured. Micromechanical structuring of the 6-in Si wafers was used to improve the thermal conversion of the sensor element. The applied plasmonic absorbers increase the infrared light absorption to >80 % for the spectral range of 3 to 5 μm, which was determined using Fourier transform infrared reflection measurements. In the first step, the performance of the sensor element was evaluated with an analog transimpedance amplifier with a feedback resistance of 5 GΩ. A specific detectivity D * > 1 · 107 cm√Hz / W was measured for the frequency range of 1 to 10 Hz. In addition, an application-specific integrated circuit was designed for the electrical signal conditioning to build a fully CMOS-compatible pyroelectric detector. It offers a simple to manufacture, flexible configuration, and digital communication interface with a signal-to-noise performance close to analog detectors. We present the measurement results of different sensor elements and detector types.

Highly Efficient Pyro-Phototronic Effect-Assisted Spectrum-Selective Colloidal Quantum Dot-Based Self-Powered Photodetector

This article presents a highly efficient pyro-phototronic effect-assisted filter-free spectrum-selective colloidal quantum dots (CQDs)-based self-powered photodetector. The reported work shows an enhanced pyro-phototronic effect and a selective response for full-width at half-maximum (FWHM) of 57 nm centered around 398 nm. The device exhibits the maximum external quantum efficiency (EQE) of 3.82% at ~400 nm under self-bias conditions, much higher than the previously reported works. The device structure consists of indium-tin oxide (ITO)-coated glass substrate/ZnO QDs/CdSe QDs/MoOx/Au, where ZnO QDs and MoOx act as charge transport layers. The device is illuminated from the backside (substrate side) to achieve the 100% illumination area. The effective pyroelectric coefficient of the device is also found to be 16.83 times higher than other works at a minimal temperature variation of 0.5 K. The device shows the maximum sensitivity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${(}{I}_{\text {ph}}/{I}_{d}{)}$ </tex-math></inline-formula> of ~330 under the self-bias condition, indicating the device’s suitability for the self-powered photodetector.

Novel photostrictive 0-3 composites: A finite element analysis

Simultaneous action of photovoltaic effect and converse piezoelectric effect will induce the photostrictive effect. In contrast to the naturally occurring photostrictive material, the present study proposes a 0-3 photostrictive composite. The current photostrictive composite comprises of poly{4,8-bis[5-(2-ethyl-hexyl) thiophen-2-yl] benzo[1,2-b:4,5-b′] dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethyl-hexyl) carbonyl] thieno[3,4-b] thiophene-4,6-diyl} (PTB7-Th) as organic photovoltaic polymer matrix and Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-35PT) as the particulates. The current study shows that the present 0-3 photostrictive composite is a suitable alternative for the most popular lead-based photostrictive material. While evaluating all the effective elastic, dielectric, piezoelectric, and pyroelectric properties of 0-3 photostrictive composite, the effect of local fluctuations was incorporated in representative volume element (RVE) using the finite element method. A finite element formulation using a degenerated shell element is derived to simulate the actuation response of the proposed 0-3 photostrictive composite. Numerical studies have been performed on cantilever and simply supported beams. The maximum tip and center deflection of cantilever beam and simply supported beam bonded with 0-3 photostrictive patch is mm and mm, respectively. The maximum value of the effective piezoelectric coefficient effective thermal expansion coefficient effective Young’s modulus and effective pyroelectric coefficient of proposed 0-3 photostrictive composite are m/V, 4.59 1.63 N/m2, and 7.57 C/m2 K, respectively, obtained at 25% volume fraction of particulates. This study opens possibilities of photostrictive coupling in composites.

Temperature Dependence of the Pyroelectric Coefficient of AlScN Thin Films

The piezoelectric and pyroelectric properties of aluminum nitride (AlN) can be further enhanced by alloying AlN with scandium nitride (ScN). However, while the pyroelectric effect can strongly affect the performance of electroacoustic devices such as surface acoustic wave (SAW) resonators, the pyroelectric properties of aluminum scandium nitride (AlScN) and their thermal dependence are not well known. In this work, the crystallographic, microstructural, and pyroelectric properties of 900 nm thick pyroelectric Al1−xScxN thin films (x = 0 to 0.3) are investigated. All films have wurtzite‐type crystal structure and are highly c‐axis oriented. The pyroelectric coefficient in the temperature range of 20–80 °C is determined by measuring the generated current as a function of sinusoidal temperature excitation. The effective pyroelectric coefficient of AlScN increases by approximately 85% in the investigated composition range. Moreover, no temperature dependence of the effective pyroelectric coefficient is observed for all samples. The increase of the effective pyroelectric coefficient is explained qualitatively by considering the contribution of primary and secondary pyroelectric effect as well as the substrate clamping.

The flexoelectric effect associated size dependent pyroelectricity in solid dielectrics

A phenomenological thermodynamic theory is used to investigate the effect of strain gradient on the pyroelectric effect in centrosymmetric dielectric solids. Direct pyroelectricity can exist as external mechanical stress is applied to non-pyroelectric dielectrics with shapes such as truncated pyramids, due to elastic strain gradient induced flexoelectric polarization. Effective pyroelectric coefficient was analyzed in truncated pyramids. It is found to be controlled by size, ambient temperature, stress, and aspect ratio and depends mainly on temperature sensitivity of flexoelectric coefficient (TSFC) and strain gradient of the truncated pyramids dielectric solids. These results show that the pyroelectric property of Ba0.67Sr0.33TiO3 above Tc similar to PZT and other lead-based ferroelectrics can be obtained. This feature might widely broaden the selection of materials for infrared detectors with preferable properties.

Effective multi-field properties of electro-magneto-thermoelastic composites estimated by finite element method approach

A finite element approach based on the micromechanics was performed to estimate the multi-field properties of electro-magneto-thermoelastic composites. The thermal field and the involved pyroelectric and pyromagnetic effect of the multi-phase composite materials were taken into account in the investigation and implemented in the finite element modeling. The multi-fields related to the electric field, magnetic field, deformation and temperature field, as well as their coupling effects of the smart composites under periodic boundary conditions were obtained numerically. Especially, by means of the homogenization approximation, the effective thermal expansion coefficients, pyroelectric coefficients, pyromagnetic coefficients and other elastic, electric, and magnetic properties for the piezoelectric material, piezomagnetic material and magnetoelectric material were calculated, respectively. Some results are compared to the theoretical predictions by the well-known Mori-Tanaka method to show good agreements.

Temperature-related effective properties and exact relations for thermo-magneto-electro-elastic fibrous composites

Based on the asymptotic homogenization method, a three-dimensional boundary value problem for two-phase periodic thermo-magneto-electro-elastic composites is presented. We consider composite materials consisting of identical parallel cylindrical fibers periodically distributed in a matrix. Both constituents are transversely isotropic and the unit-cell has rhombohedral shape. The derivation of the corresponding homogenized problem, effective coefficients and local problems is summarized. Exact relations are derived without imposing any restriction on the global behavior of such fibrous composite materials. In particular, proportionality relations linking the temperature-related effective coefficients are obtained. Simple analytical formulae are obtained for these temperature-related effective coefficients as a function of four effective elastic coefficients, and they show the existence of pyroelectric and pyromagnetic product properties in the composite material when these effects are not present at the constituents level. Moreover, the formulae are valid for any fiber cross-section geometry and periodicity. An analytical formula of the fiber area fraction for which the effective pyroelectric and pyromagnetic coefficients are maximal is given. Some numerical examples are considered in order to illustrate the relevance of the combination of the exact relations with homogenization methods. Comparisons with analytical and numerical results are included.

Effective Pyroelectric Coefficient of Layered Structures

The paper encompasses the investigation of the effective pyroelectric behavior of materials in different structures/systems such as the bimorphs and the sandwiched structure, with the variation of the temperature. Different mathematical approaches have been used to include the secondary factors contributing to the effective pyroelectric coefficient, and it has been included to obtain a consolidated expression of the same. The effective pyroelectric coefficient for few selected ferroelectric materials has been deduced using their actual physical constants to get a closer resemblance with the practical device. This paper would be a step forward to the fabrication of layered material with a higher pyroelectric coefficient for a possible energy harvesting applications also.

Micromechanical modeling of piezo-magneto-thermo-elastic composite structures: Part I – Theory

The comprehensive micromechanical models for the analysis of piezo-magneto-thermo-elastic smart composite structures with orthotropic constituents are developed. The asymptotic homogenization models are derived, the governing equations are determined. Subsequently general relations called unit cell problems are derived. They can be used to determine the effective elastic, piezoelectric, piezomagnetic, thermal expansion, dielectric, magnetic permeability , magnetoelectric, pyroelectric and pyromagnetic coefficients. The latter three sets of coefficients are particularly interesting in the sense that they represent product or cross-properties; they are generated in the macroscopic composite via the interaction of the different phases, but may be absent from some of the constituents themselves. The derived relations pertaining to the unit-cell problems and the resultant effective coefficients are very general and they are valid for any 3D geometry of the unit cell. In Part II of this work the results of the asymptotic homogenization models for practically important smart composite structures are obtained and presented graphically. ► We develop two Asymptotic Homogenization Models pertaining to 3D smart composites. ► One Model uses Maxwell's Equations. ► The second Model uses Quasi-static approximation of Maxwell's equations. ► All effective properties including product properties are determined.

Effect of temperature on the polarization distribution in BTS functional gradient ceramics

The effect of the chemical composition gradient in barium titanate-stannate (BTS) piezoelectric ceramic on the depth distribution of the effective pyroelectric coefficient was investigated. A correlation between the coordinate dependence of polarization in the sample and the polarization temperature is demonstrated.

Micromechanical analysis of magneto-electro-thermo-elastic composite materials with applications to multilayered structures

The method of asymptotic homogenization was used to analyze a periodic magnetoelectric smart composite structure consisting of piezoelectric and piezomagnetic phases. The asymptotic homogenization model is derived, the governing equations are determined and subsequently general expressions called unit-cell problems that can be used to determine the effective elastic, piezoelectric, piezomagnetic, thermal expansion, dielectric, magnetic permeability, magnetoelectric, pyroelectric and pyromagnetic coefficients are presented. The latter three sets of coefficients are particularly interesting in the sense that they represent product or cross-properties; they are generated in the macroscopic composite via the interaction of the different phases, but may be absent from the constituents themselves. The derived expressions pertaining to the unit-cell problems and the resultant effective coefficients are very general and are valid for any 3-D geometry of the unit cell. The model is illustrated by means of longitudinally-layered smart composites consisting of piezoelectric (Barium Titanate) and piezomagnetic (Cobalt Ferrite) constituents. Closed-form expressions for the effective properties are derived and the results are plotted vs. the volume fraction of the piezoelectric phase. Pertaining to the product properties of this particular magnetoelectric laminate, it is observed that the effective pyroelectric and pyromagnetic coefficients attain a maximum value at a BaTiO 3 volume fraction of 0.5 and maximum values for the magnetoelectric coefficients at a BaTiO 3 volume fraction of 0.4. Likewise, the maximum value of a magnetoelectric figure of merit (characterizing efficiency of energy conversion in longitudinal direction) is also attained at a volume fraction of 0.4.

An analytical model for predicting thermo-electro-mechanical response of 1–3 piezoelectric composites

Abstract An analytical method based on parallel and series models is developed to evaluate the performance of 1–3 piezoelectric composite where both matrix and fiber phases are piezoelectrically active. A parametric study is conducted to investigate the influence of the volume fraction of ceramic on the smart composite and the performance of the 1–3 composite for underwater acoustics and biomedical imaging has been addressed. The present model is capable of predicting the effective properties of the composite subjected to thermo-electro-mechanical loading conditions. Simulated results are compared with experimentally measured data reported in literature (Taunaumang et al., 1994 [1] ) and are found to be in reasonable agreement. The outcome of the present study demonstrates the influence of thermal effect on effective properties of the composite induces the polarization in the composite. Along the loading direction, there is a significant reduction in the effective pyroelectric coefficient of the piezocomposites, except near the monolithic ceramic fiber material.

The exact connections of the effective thermal properties of ferroelectric crystals with domain configurations

Exact connections between the effective thermal expansion and pyroelectric coefficients and the effective elastic and piezoelectric coefficients have been established for trigonal, tetragonal, and hexagonal ferroelectric crystals with compatible domain configurations, taking advantage of compatible but not necessarily uniform internal field resulted from a hydrostatic stress and uniform temperature change. These exact connections reduce the number of independent material constants, and thus the number of necessary experimental measurements, and allow the determination of the effective thermal moduli of a ferroelectric crystal from its effective electroelastic moduli. Numerical results are also presented to demonstrate the application of such exact connections.

Effective properties of thermo-electro-mechanically coupled piezoelectric fiber reinforced composites

In the present work, strength of materials based approach has been used for determination of effective coupled thermo-electro-mechanical (TEM) properties of piezoelectric fiber reinforced composite (PFRC). Rectangular representative volume element (RVE) with rectangular fibers has been considered and dependencies of effective coupled thermo-electro-mechanical coefficients of PFRC on fiber volume fraction have been studied. Results obtained for electro-mechanical coefficients have been compared with already published results [Mallik N, Ray MC. Effective coefficients of piezoelectric fiber reinforced composites. AIAA J 2003;41:704–10. Ray MC. Micromechanics of piezoelectric composites with improved effective piezoelectric constant. Int Mech Mater Des 2006;3:361–71] and show an excellent agreement. Results also show that effective thermal coefficients are reduced and the effective pyroelectric coefficients for PFRC are increased (for some fiber volume fraction range) compared to that in bulk piezoelectric materials. Model predicts strong dependence of the effective coefficients of the PFRC on the fiber volume fraction as well as elastic properties of matrix.

Effects of niobium doping on lead zirconate titanate films deposited by a sol–gel route

Niobium (Nb)-doped lead zirconate titanate (PZT) films have been prepared on platinized silicon substrates using a sol–gel method. The Zr/Ti ratios of the films are 53/47 and 40/60, and the Nb doping level ranges from 0 mol% to 3 mol%. Similar to the cases in bulk ceramics, after the doping with Nb, the remanent polarization Pr, effective transverse piezoelectric coefficients e31,c and pyroelectric coefficient p of the PZT films increase; but the longitudinal effective piezoelectric coefficient d33,c remains roughly unchanged. At the optimum Nb doping levels, the observed Pr, −e31,c and p reach a maximum value of 30 μC/cm2, 18 C/m2 and 350 μC/m2 K, respectively, for the PZT (53/47) films, and 37 μC/cm2, 7.9 c/m2 and 370 μC/m2 K for the PZT (40/60) films. Our results also reveal that there exist linear relations between p, e31,c/er and Pr.

Enhanced pyroelectric sensitivity using ferroelectric active mode detection

Active pyroelectric detection (APD), using ferroelectrics as the sensing materials, is described and compared to traditional-passive pyroelectric modes of operation. The active approach yields a number of distinct advantages over its passive counterparts, including greater effective pyroelectric coefficient and improved signal to noise ratio. Thin film test structures formed from strontium bismuth tantalate (SrBi2Ta2O9) are used to demonstrate the APD principle.

A general formula for the effective pyroelectric coefficient of composites

We have derived a general formula for the prediction of the effective pyroelectric coefficient of composites. In this relation, the pyroelectric coefficient of the composite is written as a function of the pyroelectric coefficients and dielectric constants of the constituents and the effective dielectric constant of the composite material. In contrast to other formulas in the field, shape and spatial arrangement of the components and the volume ratio are not directly involved in our relation. The influence of these is completely included in the effective dielectric constant of the composite. Therefore, the new relation gives a correct description for all kinds of connectivities and provides an easy tool for the optimization of pyroelectric composites.

A general formula for the effective pyroelectric coefficient of composites

A general formula for the effective pyroelectric coefficient of composites

Calculation of the coordinate dependences of the effective pyroelectric coefficient under conditions of rectangular heat flux modulation with the use of digital methods for signal processing

A method is proposed for determining the coordinate dependences of the effective pyroelectric coefficient with the use of digital methods for signal processing. An expression is derived for calculating the pyroelectric coefficient under conditions of heat flux modulation with rectangular pulses. The proposed method makes it possible to determine the polarization state of bulk ferroelectric materials.

Effect of electrical conductivity on poling and the dielectric, pyroelectric and piezoelectric properties of ferroelectric 0-3 composites

We have investigated the effects of electrical conductivity of the constituents on the poling behavior, dielectric, pyroelectric and piezoelectric properties of ferroelectric 0-3 composites. Modeling of polarization behavior is explored for both dc and ac poling procedures. Simulated results show that, in addition to the poling schedule, conductivity plays an important role in the poling process. Calculations are carried out for the time dependent internal electric fields induced by an ac field in dielectric measurements, by modulated temperature in pyroelectric measurement or by stress in piezoelectric measurement. Our previously developed models for dielectricity, pyroelectricity and piezoelectricity have been extended to include the additional contribution from the electrical conductivities. These can be significant for ceramic/polymer composites possessing high conductivity in the matrix phase. Calculated values based on the new model are discussed and compared with the previous models, and in particular the pyroelectric activities reported in the literature for a graphite doped lead zirconate titanate/polyurethane composite. Explicit expressions for the transient and steady state responses are given and the effective permittivity, pyroelectric and piezoelectric coefficients are derived in this paper. Remarkable enhancement in these coefficients is obtained when higher conductivity is introduced in the matrix phase.