Large Pyroelectric Coefficient Research Articles

Pyroelectric Properties and Applications of Lithium Tantalate Crystals

Lithium tantalate crystals, as a type of pyroelectric material, stand out from many other pyroelectric materials due to the advantages of high Curie temperature, large pyroelectric coefficient, high figure of merits, and environmental friendliness. Due to the pyroelectric effect caused by their spontaneous polarization, lithium tantalate crystals have broad application prospects in wide spectral bandwidth and uncooled pyroelectric detectors. This article reviews the pyroelectric properties of lithium tantalate crystals and evaluates methods for pyroelectric properties, methods for modulating pyroelectric properties, and pyroelectric detectors and their applications. The prospects of lithium tantalate thin films, doped lithium tantalate crystals, and near stoichiometric lithium tantalate crystals as response components for pyroelectric detectors are also discussed.

Large Spontaneous Polarization Ferroelectric Property, Switchable Second-Harmonic Generation Responses, and Magnetism in an Fe-Based Compound.

Since the switchable spontaneous polarization of ferroelectric materials endows it with many useful properties such as a large pyroelectric coefficient, switchable spontaneous polarization, and semiconductor, it has a wide range of application prospects, and the research of high-performance molecular ferroelectric materials has become a hot spot. We obtained a 0D organic-inorganic hybrid ferroelectric [(CH3)3NCH2CH2CH3]2FeCl4 (1) with well-defined ferroelectric domains and excellent domain inversion and exhibited a relatively large spontaneous polarization (Ps = 9 μC/m-2) and a Curie temperature (Tc) of 394 K. Furthermore, compound 1 belongs to the non-centrosymmetrical space group Cmc21 and has a strong second-harmonic generation signal. Interestingly, we also performed magnetic tests on 1, which confirmed that it is a magnetic material. This work provides clues for exploring the application of high-performance molecular ferroelectric materials in future multifunctional smart devices.

Giant Near-Room-Temperature Pyroelectric Figures-of-Merit Originating from Unusual Dielectric Bistability of Two-Dimensional Perovskite Ferroelectric Crystals

Pyroelectric materials with the capability of converting temperature changes into electrical signals have been widely used as essential elements for assembling integrated smart electronic detectors. Regarding the conversion efficiency of the voltage output, however, it is significant but quite challenging to exploit new candidates with large pyroelectricity figures-of-merit (FOMs) at room temperature. Herein, we have acquired giant near-room-temperature pyroelectric FOMs in the two-dimensional (2D) perovskite-type improper ferroelectric crystals of (BA)2(EA)2Pb3I10 (1, where BA = n-butylammonium and EA = ethylammonium), for which the room-temperature voltage FOM (Fv = 1.06 × 10–2 cm2/μC) is about 10 times as large as that of the state-of-the-art inorganic oxides (often ∼0.1 × 10–2 cm2/μC), while the peak values near the Tc are almost 2–3 orders of magnitude higher than those of the typical oxide counterparts. Such ultrahigh FOMs are mainly due to their large pyroelectric coefficients and unusual bistability of dielectric behavior, that is, an extremely small-amplitude dielectric variation caused by dipole reorientations during the ferroelectric-to-antiferroelectric phase transition at ∼315 K. This achievement of ultrahigh pyroelectric FOMs in improper ferroelectrics is in sharp contrast to the proper counterparts. Moreover, the low-cost and facile integration of crystal-based devices favors their great potential as smart pyroelectric detectors. As far as we know, the findings of giant pyroelectricity FOMs are unprecedented in 2D hybrid perovskites, which probably recall their broader prospects toward high-performance electronic device application.

Large pyroelectricity via engineered ferroelectric‐relaxor phase boundary

Abstract With growing demand for high‐sensitivity infrared detectors in industrial temperature monitoring and medical systems, high‐performance pyroelectric materials are vitally required. In this work, large pyroelectric performance is achieved in (1 − x)Pb0.99Nb0.02[(Zr0.57Sn0.43)0.937Ti0.063]0.98O3–xBaTiO3 (1 − x)PNZST–xBT ceramics by tuning the ferroelectric (FE)‐relaxor phase boundary near room temperature. The FE‐ and ergodic‐relaxor phase boundaries are engineered by breaking the long‐range antiferroelectric order with the introduction of BaTiO3. It is found that the ceramics with x = 0.15 exhibit a large pyroelectric coefficient of 11.3 × 10–4 C m–2 K–1 and figures of merit of Fi = 20.1 × 10–10 m V–1, Fv = 3.44 × 10–2 m2 C–1, and Fd = 3.87 × 10–5 Pa–1/2 around room temperature due to engineered phase boundary. Our results provide the potential technological application for ultrasensitive infrared detector and scientific insights into pyroelectric ceramic design.

Lead-Free BiFeO3 Thin Film: Ferroelectric and Pyroelectric Properties

The ferroelectric and pyroelectric properties of bismuth ferrite (BFO) epitaxial thin film have been investigated. The ferroelectric epitaxial thin layer has been deposited on strontium titanate (STO) (001) substrate by pulsed laser deposition, in a capacitor geometry using as top and bottom electrode a conductive oxide of strontium ruthenate (SRO). The structural characterizations performed by X-ray diffraction and atomic force microscopy demonstrate the epitaxial character of the ferroelectric thin film. The macroscopic ferroelectric characterization of BFO revealed a rectangular shape of a polarization-voltage loop with a remnant polarization of 30 μC/c m2 and a coercive electric field of 633 KV/cm at room temperature. Due to low leakage current, the BFO capacitor structure could be totally pooled despite large coercive fields. A strong variation of polarization is obtained in 80–400 K range which determines a large pyroelectric coefficient of about 10−4 C/m2 K deduced both by an indirect and also by a direct method.

Discovery of amantadine formate: Toward achieving ultrahigh pyroelectric performances in organics

Pyroelectrics are a class of polar compounds that output electrical signals upon changes in temperature. With the rapid development of flexible electronics, organic pyroelectrics are highly desired. However, most organics suffer from low pyroelectric coefficients or low working temperatures. To date, the realization of superior pyroelectric performance in all-organics has remained a challenge. Here, we report the discovery of amantadine formate, an all-organic pyroelectric with ultrahigh voltage figures of merit (Fv), surpassing those of all other known organics and commercial triglycine sulfate, LiTaO3 as well around room temperature. The key to the high Fv is attributed to large pyroelectric coefficients in a favorable temperature range resulting from a ferroelectric-paraelectric phase transition of second order at 327 K, small dielectric constant, and moderate heat capacity. In addition, amantadine formate is relatively lightweight, soft, transparent, low-cost, and non-toxic, adding value to its potential applications in flexible electronics. Our results demonstrate that a new type of pyroelectrics can exist in organic compounds.

Growth, Properties and Applications of Bi0.5Na0.5TiO3 Ferroelectric Nanomaterials.

The emerging demands for miniaturization of electronics has driven the research into various nanomaterials. Lead-free Bi0.5Na0.5TiO3 (BNT) ferroelectric nanomaterials have drawn great interest owing to their superiorities of large remanent polarization, high pyroelectric and piezoelectric coefficients, unique photovoltaic performance and excellent dielectric properties. As attractive multifunctional ferroelectrics, BNT nanomaterials are widely utilized in various fields, such as energy harvest, energy storage, catalysis as well as sensing. The growing desire for precisely controlling the properties of BNT nanomaterials has led to significant advancements in material design and preparation approaches. BNT ferroelectric nanomaterials exhibit significant potential in fabrication of electronic devices and degradation of waste water, which pushes forward the advancement of the Internet of things and sustainable human development. This article presents an overview of research progresses of BNT ferroelectric nanomaterials, including growth, properties and applications. In addition, future prospects are discussed.

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.

Universal Curie constant and pyroelectricity in doped ferroelectric HfO2 thin films

Abstract Pyroelectric coefficients are measured for Si, Sr, La, Al, and Gd doped HfO2 thin films as well as the solid-solution Hf0.5Zr0.5O2 composition from 280 to 440 K. Pyroelectric currents show sensitivity to the dopant used to stabilize ferroelectricity in HfO2. Large pyroelectric coefficients up to 70 μC cm−2 K−1 were measured in films with the largest remanent polarization magnitudes, La-doped HfO2 and Hf0.5Zr0.5O2. A temperature-driven ferroelectric to antiferroelectric-like transition influences the pyroelectric coefficient and is found only in Si-doped HfO2 thin films. The transition is shown to produce a decrease in the Curie constant with temperature and thus deviates from the Curie law, although most ferroelectric films reported here obey the Curie law. Independent measurements of the remanent polarization, relative permittivity, and pyroelectric coefficient are used to extract the Curie constants of the thin films. The fundamental thermodynamic relationship between the dielectric, ferroelectric, and pyroelectric properties of ferroelectric HfO2 thin films are established based on Landau theory with a universal Curie constant of 5.8 × 10−7 ± 0.46 × 10−7 K C V−1 m−1 (Landau coefficient, α0 = 1.72 × 106 ± 0.138 × 106 V m K−1 C−1) for ferroelectric HfO2 independent of doping concentration and dopant type. An electro-thermal coupling factor of 1.9 × 10−3 and a voltage responsivity figure of merit of 0.085 m2/C illustrate the promising potential of ferroelectric HfO2 thin films for use in embedded energy harvesting and infrared sensing circuits.

Gaussian soliton pairs in an unbiased photorefractive crystal due to the pyroelectric effect

The characteristics of the dynamical evolution of incoherently coupled Gaussian soliton pairs in unbiased photorefractive media forming solely due to the pyroelectric effect are studied for the first time. A parameter space spawning a large set of bright Gaussian soliton pairs in unbiased photorefractive crystals having a large pyroelectric coefficient has been found. These soliton pairs can exist if the light beams have similar polarization, equal wavelength and are mutually incoherent. A change in the temperature of the photorefractive crystal induces a temporary pyroelectric field resulting in the formation of a space-charge field. The existence curve for these soliton pairs is studied for different values of the temperature change. It is also established that both individual components of the soliton pair should have equal spatial widths for stable propagation. The whole parameter space in which these soliton pairs exist as a changeless entity has been investigated in terms of the spatial width of the soliton pair, their peak power, and the magnitude of temperature change of the crystal. The magnitude of the temperature change profoundly affects the evolution characteristics of these Gaussian soliton pairs. The stability of such soliton pairs has been demonstrated using the paraxial theory. Bistable states have been shown to exist in the system irrespective of the magnitude of the temperature change for the case when both components of the soliton pair have equal power. A lithium niobate (LN) crystal has been considered to illustrate the relevant results.

Pyroelectric Energy Conversion in Doped Hafnium Oxide (HfO2) Thin Films on Area‐Enhanced Substrates

Low‐grade heat sources are abundant yet challenging to use for energy harvesting. Herein, the pyroelectric effect in Si‐doped HfO2 thin films is used to demonstrate thermal‐electric energy conversion. The 20 nm thin films are grown on an area‐enhanced substrate via atomic layer deposition, which enhances the power output by a factor of 19 in comparison to planar materials. Ferroelectric and pyroelectric properties of the Si‐doped HfO2 are investigated, and a large pyroelectric coefficient of –1442 μC m−2 K−1 is measured. Wireless power distribution using an infrared laser and pyroelectric Si‐doped HfO2 receiver is demonstrated, where Brayton‐style thermodynamic cycles are used to enhance the efficiency compared with simple resistive harvesting. Thereby, energy conversion cycles at 5 Hz produce net powers of 0.75 μW cm−2. The operating conditions of the power‐beaming circuit are optimized, and the performance is found to be ultimately limited by the series resistance of the electrodes. The thermal efficiency of the HfO2‐based pyroelectric is analyzed relative to classical pyroelectrics, and the loss mechanisms are discussed.

Piezoelectric and pyroelectric properties of (001) oriented KNbO3 film

A phenomenological Landau-Devonshire theory is used to investigate the “misfit strain-temperature” phase diagram and physical properties of (001) oriented KNbO3 film. Three ferroelectric phases, such as c phase, aa phase, and γ phase, occur in the phase diagram. In-plane compressive misfit strain is beneficial to form c phase and tensile strain makes aa phase stable. Physical properties of KNbO3 film largely depend on misfit strain and electric field. At room temperature, γ phase of KNbO3 film with the tensile misfit strain has larger piezoelectric and pyroelectric coefficients than that of c phase with the compressive strain. Large piezoelectric and pyroelectric coefficients are 180 pm/V and 8.5 × 10−4 C/m2K respectively at the electric field of 100 KV/cm and misfit strain of 6.7 × 10−3, which are comparable with the experimental results of Pb(ZrxTi1−x)O3 film. Therefore, choosing the appropriate substrates can be used to improve the physical properties of KNbO3 film. In addition, the applied electric field decreases the dielectric, piezoelectric and pyroelectric properties of (001) oriented KNbO3 film.

Structure analysis and systematical electric properties investigation of PSN–PMN–PT single crystal

A novel Pb(Sc1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PSN–PMN–PT) single crystal with large size ϕ25 mm × 40 mm was grown by the Bridgman technique. The crystal was cut along [100] orientation with composition of 6PSN–63PMN–31PT, and then its structure and electric properties were investigated systematically. Raman test demonstrates that the crystal is typical relaxor ferroelectrics with perovskite structure. At room temperature, [100]-oriented 6PSN–63PMN–31PT crystal shows the excellent electric properties, such as the dielectric constant er = 4793, the piezoelectric constant d33 = 1237 pC/N, and the remanent polarization Pr = 34.41 µC/cm2, respectively. It is more important that the large coercive field Ec = 8.17 kV/cm in [100]-oriented 6PSN–63PMN–31PT crystal is almost four times than that of PMN–PT, even higher than that of Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT) and Pb(Lu1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PLN–PMN–PT), indicating its potential application for high-power transducers. With elevating temperature, the [100]-oriented 6PSN–63PMN–31PT crystal shows the large pyroelectric coefficient p = 3.49 × 10−2 C/m2/K at phase transition temperature, and the related figures of merit (FOMs) for current responsivity Fi, for voltage responsivity Fv and for detectivity FD increase from 1.968 × 10−10 m/V, 0.00485 m2/C and 0.59 × 10−5 Pa−1/2 to 1.396 × 10−8 m/V, 0.054 m2/C, and 52.94 × 10−5 Pa−1/2, respectively. Furthermore, the thermal strain at heating process was analyzed for unpoled and poled crystal.

Enhanced energy storage and pyroelectric properties of highly (100)-oriented (Pb1−x−yLaxCay)Ti1−x/4O3 thin films derived at low temperature

Highly (100)-oriented (Pb1−x−yLaxCay)Ti1−x/4O3 (x=0.15, y=0.05; x=0.1, y=0.1; x=0.05, y=0.15) thin films were deposited on Pt/Ti/SiO2/Si substrates at a low temperature of 450 °C via a sol–gel route. It was found that all the (Pb1−x−yLaxCay)Ti1−x/4O3 thin films could be completely crystallized and the content of La/Ca showed a significant effect on the electrical properties of films. Among the three films, the (Pb1−x−yLaxCay)Ti1−x/4O3 (x=0.1, y=0.1) thin film exhibited the enhanced overall electrical properties, such as a low dielectric loss (tan⁡δ<0.08) and leakage current (J∼4.6×10−5 A/cm2), a high recoverable energy density (Wre ∼ 15 J/cm3), as well as a large pyroelectric coefficient (p ∼ 190 μC/m2K) and figure of merit (Fd′∼77 μC/m2K). The findings suggest that the fabricated thin films with a good (100) orientation can be an attractive candidate for applications in Si-based energy storage and pyroelectric devices.

High performance Bi0.5Na0.5TiO3-BiAlO3-K0.5Na0.5NbO3 lead-free pyroelectric ceramics for thermal detectors

Both high pyroelectric properties and good temperature stability of ferroelectric materials are desirable when used for applications in infrared thermal detectors. In this work, we report lead-free ternary 0.97(0.99Bi0.5Na0.5TiO3-0.01BiAlO3)-0.03K0.5Na0.5NbO3 (BNT-BA-KNN) ceramics, which not only exhibits a large pyroelectric coefficient (p ∼ 3.7 × 10−8 C cm−2 K−1) and figures of merit (Fi, Fv, and Fd) but also shows excellent thermal stable properties. At room temperature, Fi, Fv, and Fd are determined as high as 1.32 × 10−10 m/V, 2.89 × 10−2 m2/C, and 1.15 × 10−5 Pa−1/2 at 1 kHz and 1.32 × 10−10 m/V, 2.70 × 10−2 m2/C, and 1.09 × 10−5 Pa−1/2 at 20 Hz, respectively. During the temperature range of RT to 85 °C, the achieved p, Fi, Fv, and Fd do not vary too much. The high depolarization temperature and the undispersed ferroelectric-ergodic relaxor phase transition with a sharp pyroelectric coefficient peak value of ∼400 × 10−8 C cm−2 K−1 are suggested to be responsible for this thermal stability, which ensures reliable actual operation. The results reveal the BNT-BA-KNN ceramics as promising lead-free candidates for infrared thermal detector applications.

Effects of electric field induced polarization on dielectric tunability and pyroelectric coefficient

ABSTRACTBased on the Devonshire theory, a ratio of two thermodynamic parameters, a polarization – temperature coefficient, is found as the crucial for pyroelectric and dielectric tunability effects. Smaller ratio corresponds to larger degree of shift of dielectric peak and larger E-induced polarization. The materials will have higher temperature-stable dielectric tunability suitable for microwave devices. Larger ratio corresponds to larger change of electric hysteresis loop in shape and size with decreasing temperature from the Curie point. The materials will have larger pyroelectric coefficient. An experimental law that pyroelectric coefficient over square root of dielectric constant is a constant is derived.

X-ray source on the basis of the piroelectric crystal Sr0.61Ba0.39Nb2O6

The properties of X-ray source based on Sr0.61Ba0.39Nb2O6 crystals (SBN-61) having a large pyroelectric coefficient γ = 85 nC/(cm2K) was studied. When the crystal was heated to 60 ° C, X-rays from a tungsten target with energy of 8.4 keV were detected. The maximum energy of the electron beam was 52 keV. The visualization of the electron beam with a grid electrode and a fluorescent screen showed that the electron beam was inhomogeneous in the polar plane of the crystal and varied during heating.The radiation intensity was unstable in time. The work of the X-ray source was limited to electrical breakdowns between the polar faces of the crystal. When the crystal was cooled, there was no X-ray emission, which could be due to the depolarization of the crystal by the total electric field or as a result of electrical breakdowns. The crystals SBN-61 and LiNbO3 are compared.

Tunable Pyroelectricity around the Ferroelectric/Antiferroelectric Transition

AbstractThe pyroelectric performance of Pb0.99Nb0.02[(Zr0.57Sn0.43)0.92Ti0.08]0.98O3 ceramics was quantified by dielectric, polarization, and specific heat capacity measurements. The tunability of pyroelectric properties upon electric field application was studied as a function of temperature. The large pyroelectric coefficient of 0.28 C m−2 K−1 was associated with the ferroelectric (FE)–antiferroelectric (AFE) phase transition. The pyroelectric coefficient can be tuned over a broad temperature range of almost 40 K above the zero electric field phase transition. Electrical and thermal measurements were used to estimate various pyroelectric figures of merit. Pyroelectric figures of merit are almost three order of magnitude higher than those previously reported in FE materials. The large pyroelectric properties indicate that the investigated material is a promising candidate for many pyroelectric applications.

A Game Changer: A Multifunctional Perovskite Exhibiting Giant Ferroelectricity and Narrow Bandgap with Potential Application in a Truly Monolithic Multienergy Harvester or Sensor.

An ABO3 -type perovskite solid-solution, (K0.5 Na0.5 )NbO3 (KNN) doped with 2 mol% Ba(Ni0.5 Nb0.5 )O3-δ (BNNO) is reported. Such a composition yields a much narrower bandgap (≈1.6 eV) compared to the parental composition-pure KNN-and other widely used piezoelectric and pyroelectric materials (e.g., Pb(Zr,Ti)O3 , BaTiO3 ). Meanwhile, it exhibits the same large piezoelectric coefficient as that of KNN (≈100 pC N-1 ) and a much larger pyroelectric coefficient (≈130 µC m-2 K-1 ) compared to the previously reported narrow-bandgap material (KNbO3 )1-x -BNNOx . The unique combination of these excellent ferroelectric and optical properties opens the door to the development of multisource energy harvesting or multifunctional sensing devices for the simultaneous and efficient conversion of solar, thermal, and kinetic energies into electricity in a single material. Individual and comprehensive characterizations of the optical, ferroelectric, piezoelectric, pyroelectric, and photovoltaic properties are investigated with single and coexisting energy sources. No degrading interaction between ferroelectric and photovoltaic behaviors is observed. This composition may fundamentally change the working principles of state-of-the-art hybrid energy harvesters and sensors, and thus significantly increases the unit-volume energy conversion efficiency and reliability of energy harvesters in ambient environments.

PLZT microfibers volume gradients and anisotropy

ABSTRACTElectrocaloric materials for a new generation of cooling elements utilize the temperature dependence of spontaneous polarization in crystalline materials to harvest waste heat. From published results in particular (Pb0.93La0.07)(Zr0.65Ti0.35)O3 composition, have the largest pyroelectric coefficient. The most effective form for such applications is micro-fiber form, due to small heat capacitance allowing quick response time, even for nano second laser excitation. The presented work provides a consistent set of examinations of structural, ferroelectric and piezoelectric properties of damaged ceramics in fiber form and its comparative analysis to bulk to get practical knowledge of the processes occurring during fiber manufacture, to effectively prevent its destruction.