Pyroelectric Applications Research Articles

Self‐Poled Heteroepitaxial Bi(1−x)DyxFeO3 Films with Promising Pyroelectric Properties

AbstractPyroelectric materials are very promising for thermal energy harvesting applications. To date, lead‐based systems are the foremost studied materials in this field. A facile and simple metal organic chemical vapor deposition route is applied for the fabrication of lead‐free, high quality, epitaxial Bi(1−x)DyxFeO3 (x = 0, 0.06, 0.08, 0.11) thin films deposited on conductive SrTiO3:Nb (100) single crystal substrates. The films are studied by structural, morphological, compositional, and functional characterization. The correlation between the Dy‐doping amount and the dielectric properties is thoroughly investigated. Unipolar polarization–electric field loops and permittivity measurements show the important impact of Dy on ferroelectric, dielectric, and pyroelectric properties. Dy doping increases considerably the dielectric response, but much more the pyroelectric coefficient, up to a concentration of 8% Dy. The films are self‐poled, which is an ideal situation for pyroelectric applications. The best figure of merit for pyroelectric energy harvesting, FE, is 82 J m−3 K−2, showing a factor increase of 2.6 as compared to the undoped film of the sample series. It constitutes a factor 4.5 improvement as compared to previous results obtained on BiFeO3 based thin films.

Enhanced Pyroelectric Performance of Lead-Free Zn-Doped Na1/2Bi1/2TiO3-BaTiO3 Ceramics.

Lead-free Na1/2Bi1/2TiO3-BaTiO3 (NBT-BT) has gained revived interest due to its exceptionally good high power properties in comparison to commercial lead-based piezoelectrics. Recently, Zn-modified NBT-BT-based materials as solid solution and composites have been reported to exhibit enhanced depolarization temperatures and a high mechanical quality factor. In this work, the pyroelectric properties of Zn-doped NBT-6mole%BT and NBT-9mole%BT ceramics are investigated. The doped compositions of NBT-6BT and NBT-9BT feature a relatively stable pyroelectric property in a wide temperature range of ~37 K (300–330 K) and 80 K (300–380 K), respectively. A threefold increase in detector figure of merit is noted for 0.01 mole Zn-doped NBT-6mole% BT at room temperature in comparison to undoped NBT-6mole%BT and this increase is higher than those of major lead-free materials. A broad range of the temperature-independent behavior for the figures of merit was noted (303–380 K) for Zn-doped NBT-6mole% BT, which is 30 K higher than the undoped material. The large pyroelectric figures of merit and good temperature stability renders Zn-doped NBT-BT an ideal candidate for pyroelectric detector and energy harvesting applications.

Recent Advances in Pyroelectric Materials and Applications.

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.

Low hysteresis and enhanced figure-of-merit of pyroelectric energy conversion at compatible phase transformation

The pyroelectricity of polar materials provides great potential for electricity generation from waste heat. The pyroelectric effect of the material can be magnificently enhanced at a first-order phase transformation due to the abrupt jump in spontaneous polarization within a narrow temperature range. Here, we show that the performance of energy conversion by phase transformation is inversely resonant with the hysteresis of thermally driven structural transformations in a (Ba1−xSrx) (Hf0.02Ce0.005Ti0.975)O3 system, corresponding to a singular lattice distortion mode satisfying the crystallographic compatibility condition. Among the finely tuned Sr compositions from 0.04 to 0.10, we discovered that Sr0.07 composition is a promising material candidate in this material system for pyroelectric energy conversion. Our work suggests a rational strategy of material development for pyroelectric energy conversion applications.

Aging in Ferroelectric Si‐Doped Hafnium Oxide Thin Films

The hafnium oxide (HfO2) material system offers a unique combination of outstanding physical properties, that enable a manifold of novel integrated ferroelectric, piezoelectric, and pyroelectric applications. Long‐term stability is an essential concern for nonvolatile memory devices, sensors, and nanoelectromechanical systems. Herein, the aging effects of the pyroelectric response in polycrystalline Si‐doped HfO2 thin films in the field‐free case are reported. It is observed that aging effects are accelerated by high temperatures, lower film thicknesses, and higher dopant concentration. The decay of the pyroelectric coefficients and the dielectric permittivity exhibits a logarithmic time dependence. The full pyroelectric response is restored by repeated electric field cycling (i.e., deaging). After the aging process, a significant internal bias field is observed. It is concluded that the migration of positively charged oxygen vacancies in the films is responsible for this aging process.

Enhanced pyroelectric response at morphotropic and field-induced phase transitions in ferroelectric hafnium oxide thin films

The hafnium oxide material class is characterized by the coexistence of several polymorphs between which phase transitions are induced by means of composition and external electric fields. Pyroelectric materials, which convert heat into electrical energy, exhibit the largest response at such morphotropic or field-induced phase transitions. The hafnium oxide material system is of special interest for pyroelectric applications since it allows for scalable and semiconductor-compatible fabrication. Here, we report large pyroelectric coefficients at the morphotropic transition from the ferroelectric orthorhombic to the centrosymmetric tetragonal phase. The electric field-induced transition between these two phases in doped HfO2 is found to yield large pyroelectric coefficients of up to −142 µCm−2 K−1, a value that is 20 times larger compared to AlN.

Ferroelectric Ceramics for Pyroelectric Detection Applications: A Review.

Dynamic temperature sensing and infrared detection/imaging near room temperature are critical in many applications including invasive safety alarming, energy conversion, and public health, in which ferroelectric (FE) materials play an extremely important role due to their pyroelectricity. As a result, over the past few decades many efforts have been made to improve the understanding of pyroelectrics, explore new pyroelectric materials, and promote their practical applications. In this review, we consider the pyroelectric parameters and the two pyroelectric operation modes. Then based on the operation modes, we review recent achievements in the FE ceramic materials for pyroelectric detection applications, including Pb(Zr,Ti)O3-based, (Bi,Na)TiO3-based, (Sr,Ba)NbO3-based, Pb(Sc,Ta)O3-based, (Ba,Sr)TiO3-based, and Pb(Zr,Sn,Ti)O3-based systems. This review will attempt to provide guidance for further improvements of the pyroelectric properties of these materials and consider future exploration of new FE and other material candidates for use in temperature and infrared sensing/detection applications.

Pyroelectric catalysis

Thermal energy derived from temperature fluctuation is one of the most clean natural energy sources in our living environment. Pyroelectric materials that feature for temperature oscillation dependent spontaneous polarization can generate usable electrical power and polarized charge carriers with a high energy conversion efficiency. Thus, pyroelectrics emerge as catalysts, which provide a promising approach to alleviating severe environmental contamination, energy crisis and biomedical issues. In this review, a comprehensive summary with first insight on the research progress of pyroelectric catalysis was provided. It starts with the introduction of some typical pyroelectric materials and pyroelectric effects. Then the fundamentals and mechanisms of pyroelectric catalysis were proposed. Highlighted are the pyroelectric catalytic applications, including disinfection and dynamic therapy, decomposition of pollutants and water splitting, and the strategies for enhancing pyroelectric catalytic efficiency put forward from diverse perspectives. Finally, the current challenges and future prospects in pyroelectric catalysis are discussed as a conclusion. This review provides a timely and comprehensive summary on pyroelectric catalysis. The typical materials, fundamentals, mechanisms and diverse applications of pyroelectric catalysis, including disinfection and dynamic therapy, decomposition of pollutants and water splitting, were demonstrated. The strategies for enhancing pyroelectric catalytic efficiency were summarized from diverse perspectives. • Some typical pyroelectric materials and pyroelectric effects were introduced. • The fundamentals and mechanisms of pyroelectric catalysis were proposed. • Diverse pyroelectric catalytic applications are highlighted. • Strategies for enhancing pyroelectric catalytic efficiency were proposed.

Pyroelectric energy harvesting and ferroelectric properties of Pb x Sr1- x TiO3 ceramics

ABSTRACT Pb x Sr1-x TiO3 (PST) (x = 0.3, 0.35 and 0.40, abbreviated as PST30, PST35 and PST40, respectively) ceramics were prepared by solid-state reaction route. Coexistence of tetragonal and cubic phase of ceramics is confirmed by X-ray diffraction pattern at room temperature (RT). Temperature-dependent dielectric permittivity εr measurements showed that Pb2+ doping increased the phase transition temperature of ferroelectric (FE) to paraelectric (PE) phase. The temperature-related polarization-electric field (P-E) measurements were performed to study the FE properties of PST ceramics. Phase transition from FE to PE was observed in P-E measurements. Furthermore, pyroelectric energy harvesting performance was evaluated based on Olsen cycle. The calculated results of pyroelectric energy harvesting density (ND ) showed that PST35 ceramic with ND = 283 kJ/m3 (∆T = 70°C, EL = 2.5 kV and EH = 40 kV) is most potential for pyroelectric energy harvesting application near RT among all samples.

Optimizing the Piezoelectric Strain in ZrO2- and HfO2-Based Incipient Ferroelectrics for Thin-Film Applications: An Ab Initio Dopant Screening Study.

HfO2 and ZrO2 have increasingly drawn the interest of researchers as lead-free and silicon technology-compatible materials for ferroelectric, pyroelectric, and piezoelectric applications in thin films such as ferroelectric field-effect transistors, ferroelectric random access memories, nanoscale sensors, and energy harvesters. Owing to the environmental regulations against lead-containing electronic components, HfO2 and ZrO2 offer, along with AlN, (K,Na)NbO3- and (Bi0.5Na0.5)TiO3-based materials, an alternative to Pb(ZrxTi1-x)O3-based materials, which are the overwhelmingly used ceramics in industry. HfO2 and ZrO2 thin films may show field-induced phase transformation from the paraelectric tetragonal to the ferroelectric orthorhombic phase, leading to a change in crystal volume and thus strain. These field-induced strains have already been measured experimentally in pure and doped systems; however, no systematic optimization of the piezoelectric activity was performed, either experimentally or theoretically. In this screening study, we calculate the ultimate size of this effect for 58 dopants depending on the oxygen supply and the defect incorporation type: substitutional or interstitial. The largest piezoelectric strain values are achieved with Yb, Li, and Na in ZrO2 and exceed 40 pm V-1 or 0.8% maximal strain, which exceeds the best experimental findings by a factor of 2. Furthermore, we discovered that Mo, W, and Hg make the polar-orthorhombic phase in the ZrO2 bulk stable under certain circumstances, which would count in favor of these systems for the ceramic crystallization process. Our work guides the development of the performance of a promising material system by rational design of the essential mechanisms so as to apply it to unforeseen applications.

Iridium oxide top electrodes for piezo- and pyroelectric performance enhancements in lead zirconate titanate thin-film devices

Iridium oxide films of various morphologies are produced by manipulating the reactive gas flow rate in a reactive sputtering process. This study explores the benefits of using planar and nanostructured IrOx top electrodes for Pb(Zr0.52Ti0.48)O3 (PZT) devices employed in piezoelectric and pyroelectric applications in comparison with conventional platinum electrodes. For the first time, the Young’s modulus of a planar IrOx thin film was directly measured to be 300 ± 15 GPa. The piezoelectric performance of devices with planar IrOx showed up to 245% more strain compared to those capped with a Pt electrode. Nanostructured, 2D IrOx platelet networks are observed for films deposited with high oxygen flow rates. The compatibility with various cleanroom processes, such as liftoff, ultrasonic cleaning, and deposition on etched surfaces, is tested for the IrOx nanostructured layers. These films are shown to have low optical reflectivity while retaining good PZT thin-film capacitor polarization and dielectric permittivity. An improved pyroelectric energy harvesting figure of merit by a factor of 2.5× was observed for the IrOx compared to Pt films on the same PZT material.

High beta-phase processing of polyvinylidenefluoride for pyroelectric applications

It is well known that poly(vinylidene fluoride) (PVDF) crystallizes in semi polymorphic crystalline forms of α, β, γ,-phases. The piezo- as well as pyroelectric properties of PVDF is strongly dependent on its β-crystalline phase. These features make it suitable for sensors and battery applications. Thin films of PVDF are widely used in recent thermal camera sensors. In this study, optimum β-crystalline phase of PVDF thin film can be produced easily via a single-step process by crystallization from gel states in the presence of corona fields. FTIR- spectroscopy investigations indicate high volume fraction of β-phases for such films. The measured pyroelectric coefficient of 33 ± 2 C/m2K exhibits a comparable result with those reported from conventionally obtained β- phase PVDF foils which requires complex treatments.

Application study of Mn-doped PIN-PMN-PT relaxor ferroelectric crystal grown by Vertical Gradient Freeze method

A 3-inch Mn:PIN-36%PMN-32%PT (Generation III) relaxor ferroelectric crystal was grown using the Vertical Gradient Freeze method. Crystals of [1, 11] and [111] orientations were prepared and studied, evaluating their dielectric constants, piezoelectric coefficients, electromechanical coupling coefficients, loss tangents and pyroelectric coefficients. It is shown that in pyroelectric applications, [111]-poled crystals are particularly suitable for high performance sensors due to a relatively high pyroelectric coefficient, low loss tangent. In addition, the specific heat is lower as compared to LiTaO3. It is also shown that the alternating current (AC) poling has a more significant effect on the [001]-poled crystal than on the [011]- and [111]-poled crystals due to the lattice distortion induced by a strong electric field along the [001] direction.

Tunable pyroelectricity, depolarization temperature and energy harvesting density in Pb(Lu0.5Nb0.5)O3-xPbTiO3 ceramics

The ferroelectric to antiferroelectric (FE-AFE) phase boundary design based on orthorhombic AFE phase and tetragonal FE phase is an effective method to develop high-performance pyroelectric materials due to the complete release of large electrical polarization in FE-AFE phase transition. Herein, we report the phase structure evolution in (1-x)Pb(Lu0.5Nb0.5)O3-xPbTiO3 (abbreviated as PLNT100x) ceramic system based on the relationship of tolerance factors versus electronegativity differences. The composition/temperature effects on FE-AFE phase transition behavior, pyroelectricity, depolarization temperature (Td) and energy harvesting performance were investigated systematically. Obviously, PLNT system displays superior pyroelectric characteristics as well as high Td. The maximum pyroelectric peak was 4.50 μC·cm−2·K − 1 over a wide temperature range from 28 °C to 167 °C. In addition, the obtained maximum pyroelectric energy harvesting density was 1.66 J/cm3 which was much higher than the currently reported values, indicating a potential candidate for pyroelectric energy conversion applications. Based on the modified Ginzburg−Landau−Devonshire (GLD) phenomenology, the composition/temperature driven phase transitions were discussed, and the temperature−electric field (T − E) phase diagram was accordance with actual phase diagram based on the experimental data.

Ferroelectric Oxide Thin Film with an Out-of-Plane Electrical Conductivity.

Ferroelectricity and electrical conductivity are two fundamentally incompatible properties that are difficult to simultaneously achieve in a material. Here, we combine these two contradictory properties by embedding conducting SrNbO3 micro/nanopillars into a ferroelectric SrNbO3.5 (i.e., Sr2Nb2O7) thin film. The high-Tc ferroelectric SrNbO3.5 thin film is epitaxially grown on a LaAlO3 substrate by pulsed laser deposition. The conducting SrNbO3 micro/nanopillars are introduced into the film via an electron-irradiation-induced SrNbO3.5-to-SrNbO3 phase transformation triggered by a focused electron beam. The sizes and distribution of the SrNbO3 micro/nanopillars can be accurately controlled through artificial manipulation of the electron-irradiation-induced SrNbO3.5-to-SrNbO3 phase transformation. The ferroelectric SrNbO3/SrNbO3.5 thin film with an in-plane polarization exhibits an electrical conductivity in the out-of-plane direction. Such conducting ferroelectric thin films may lead to the discovery of plentiful physical phenomena and have great potential for pyroelectric, photoelectric, and multiferroic applications.

Black aluminum-coated Pt/Pb(Zr0.56Ti0.44)O3/Pt thin film structures for pyroelectric energy harvesting from a light source

A black aluminum (B-Al) film was deposited onto the surface of a stack structure of platinum/Pb(ZrxTi1 − x)O3/platinum (Pt/PZT/Pt) to convert light into a heat variation and the heat variation into a polarization change. A comparison was performed between B-Al/Pt/PZT/Pt and conventional Pt/PZT/Pt structures. An absorbance higher than 95% was measured for the B-Al layer over a large range of wavelengths varying from 350 nm to 1000 nm. The theoretical model shows that heat diffusion was extremely fast through the layers, and the sample holder played a key role in the variation and stabilization of the system temperature. A doubled variation of the polarization was observed when the light was applied onto the surface of the stack structure with stable B-Al on the top. This behavior was interpreted by the larger temperature variations induced under the highly absorptive B-Al layers, in good correlation with the theoretical model prediction based on the heat fluxes in the structures. This result is very promising for possible pyroelectric energy harvesting applications.

On the potentialities of the Ba0.20Na0.80Ti0.20Nb0.80O3 lead-free composition for pyroelectric applications

Ba0.20Na0.80Ti0.20Nb0.80O3 ceramics were synthetized and their applicability as promising pyroelectric materials is discussed. Structural investigations show the existence of two polymorphic phases, cubic and tetragonal symmetries, that are pointed out as responsible for the high pyroelectric response observed close to room temperature. Dielectric and specific heat measurements clearly show a phase transition like region separating two different electric and thermal behaviors, attesting the existence of two distinct structural symmetries. The figures of merit comprising the main pyroelectric applications are reported and unambiguously indicate the high potentiality and applicability of the Ba0.20Na0.80Ti0.20Nb0.80O3 ceramics for pyroelectric detection-based technologies.

Lead-free 0.95(K0.6Na0.4)NbO3-0.05(Bi0.5Na0.5)ZrO3 ceramic for high temperature dielectric, ferroelectric and piezoelectric applications

Environment-friendly 0.95(K0.6Na0.4)NbO3-0.05(Bi0.5Na0.5)ZrO3(KNN-BNZ) ceramic have been prepared via high energy ball-milling followed by sintering. The effect of sintering temperature on the structural and piezoelectric properties has been studied and optimization of sintering temperature was carried out. X-ray diffraction (XRD) reveals the coexistence of tetragonal and rhombohedral phases for all the samples sintered at different temperatures. The ceramic sample sintered at 1150 °C showed high piezoelectric charge coefficient (d33 = 340 pC/N) with uniform and dense grains. Relaxor type ferroelectric behaviour with Curie phase temperature around 347 °C (at 1 kHz) was obtained. Well saturated and fatigue resistant P-E hysteresis loops with a remnant polarization (Pr) of 19.58 μC/cm2 and a coercive field (Ec) of 14.24 kV/cm were obtained at room temperature. A high value of pyroelectric coefficient (p ∼1855.1 μC m−2oC−1) was obtained in the temperature range 90–150 °C suitable for pyroelectric applications. Further, piezoelectric generator was fabricated using KNN-BNZ ceramic. An open circuit voltage of ∼6.2 V was generated from the device under periodic compressive force of 2 kgf. Thus, 0.95(K0.6Na0.4)NbO3-0.05(Bi0.5Na0.5)ZrO3 ceramic can serve as promising material for various electromechanical, ferroelectric and pyroelectric based devices.

Large Area Thick Films of PVDF‐TrFE and Relaxor‐Ceramics for Piezo‐ and Pyroelectric Applications

AbstractWearable electronics, sensors, and energy harvesting devices are gaining an ever increasing importance in consumer products. Their success is, however, contingent on the availability of flexible and cost‐effective functional materials. The present paper presents an up‐scaled processing route for 0–3 thick film composites of the ferroelectric polymer polyvinylidenefluoride‐trifluoroethylene and a relaxor ceramic. Different compositions are investigated for pyro‐ and piezoelectric applications. Various samples are produced via tape casting and spin‐coating as freestanding and supported films of up to 600 × 200 mm² and on 150 mm silicon wafers, respectively. The samples are characterized in terms of thickness and roughness reproducibility, mechanical properties, and impedance. It is shown that good reproducibility and quality of the films can be realized. Depending on the application targeted (pyroelectric or piezoelectric), specific compositions together with the suitable poling process are presented. For instance, a composite with 24 vol% ceramic shows highest pyroelectric properties together with lowest piezoelectric thickness coefficient (d33) when poled for pyroelectric applications. On the other hand, a composite with 50 vol% ceramic exhibits a d33 of 100 pm V−1 that is unsurpassed for this type of composites. These properties are advantageous in a large variety of applications, including wearable devices.

Enhanced ferroelectric properties and crystal structure of TGS0.74P0.26 single crystals

The single crystals of triglycine sulpho phosphate (TGS0.74P0.26) were grown by slow evaporation method with 0.6 M of phosphoric acid in the growth solution. The crystal structure of the grown crystal is refined with 0.74 sulphur and 0.26 phosphorous occupancy with the formula of TGS0.74P0.26 using single crystal x-ray diffraction analysis. The dielectric, ferroelectric and pyroelectric properties of the TGS0.74P0.26 single crystals were investigated. The coercive field (Ec) and internal bias field (Ib) values are 8 kV/cm and 1.4 kV/cm, respectively and these values are found increased compared to the pure TGS and also low dielectric loss was observed. The pyroelectric coefficient of TGS0.74P0.26 crystal is 0.023 µC/cm2/°C and the pyroelectric figure of merit for current, voltage and detectivity are Fi = 105 pm/V, Fv = 0.055 m2/C and Fd = 22 µPa−1/2 respectively. Enhanced ferroelectric properties were observed when compared to the pure TGS crystals. The figure of merit for the detectivity (Fd) shows higher values when compared with that of the well-known materials such as PZT (11.5 µPa−1/2) and other lead free materials such as SBN (7.21 µPa−1/2) and CSBN (12 µPa−1/2). With these excellent properties, the TGS0.74P0.26 single crystal can be a promising material for the pyroelectric detector applications.