High Pyroelectric Response Research Articles

Exploring Electro‐Thermal Interconversion in Oxide Superlattices Across Polarization Behavior Transition

AbstractDue to the great demand for global energy consumption, electro‐thermal energy interconversion has drawn great attention. Ferroelectrics as promising candidates realize energy conversion through pyroelectric and electrocaloric effects, but their efficiency is not sufficiently high. Herein, using phase‐field simulations, it is demonstrated that superlattices with polar topologies tend to have various polarization behaviors, and the antiferroelectric‐ to paraelectric‐like phase transition induces a large polarization change and thus a high pyroelectric response. In KNbO3/KTaO3 superlattices, the pyroelectric energy conversion has a scaled efficiency of 50% and the equivalent ZT of 7.2, and the electrocaloric cooling temperature reaches 40 K. The operation temperature can be tuned by changing the thickness of the superlattice. The results reveal that oxide superlattices are competitive in energy harvesting and conversion, thus creating new application prospects for polar topologies.

High pyroelectric response over a broad temperature range in NBT-BZT: SiO2 composites for energy harvesting

Pyroelectric energy harvesting is considered a highly promising technology for converting low-grade waste heat into electricity, but the practical applications of pyroelectric generators is limited by the their poor energy densities and instability. In this work, we construct SiO2 networks with low heat capacities in NBT-BZT ceramics. These networks improve the heat transfer (dT/dt) and broaden the pyroelectric temperature region of the composites by reducing heat absorption capacity, thereby leading to high pyroelectric energy density and stability. The temperature range of the NBT-BZT composite with 0.1 wt% SiO2 for pyroelectric coefficient higher than 20 × 10−4 C m−2 K−1 is increased to 20 °C, This increase results in the high thermostability of energy harvesting. In addition, the NBT-BZT: 0.1 wt% SiO2 composites show an optimized pyroelectric energy density of 110 u J cm-3, nearly three times that of the pure NBT-BZT ceramics. This work is beneficial for the application of high-performance pyroelectric materials for devices used in energy harvesting.

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.

Structural Transition and Electrical Properties of (1 − x)(Na0.4K0.1Bi0.5)TiO3-xSrTiO3 Lead-Free Piezoceramics

(1 − x)(Na0.4K0.1Bi0.5)TiO3-xSrTiO3 (NKBT-xST) ceramics with x = 0 mol.%, 3 mol.%, and 5 mol.% (0ST, 3ST, and 5ST) have been prepared by a conventional solid-state reaction method and their ferroelectric, electrostrictive, and pyroelectric properties investigated. Addition of ST considerably disrupted the long-range ferroelectric order of NKBT-xST ceramics, and the 5ST ceramic exhibited ergodic relaxor phase structure. T FR shifted to near or below room temperature for 5ST ceramic, accompanied by a significant decline of ferroelectricity and enhanced strain. As the temperature approached T FR, the NKBT-xST ceramics exhibited predominantly electrostrictive effect, and the 5ST ceramic presented relatively high electrostrictive coefficient Q 33 of 0.0193 m4/C2. High pyroelectric response was observed for 0ST, 3ST, and 5ST ceramics in the vicinity of T FR due to the large polarization release during the ferroelectric–relaxor structural transition. The 5ST ceramic exhibited high and frequency-insensitive (100 Hz to 10 kHz) room-temperature pyroelectric properties with pyroelectric coefficient p of 656 μC m−2 K−1 and figures of merit F i, F v, and F d reaching 233 pm/V, 0.013 m2/C, and 7.61 μPa−1/2, respectively, indicating that 5ST ceramic is a promising candidate to replace PZT-based ceramics.

Effects of glass additions on high pyroelectric response of low-temperature sintered Pb0.87Ba0.1La0.02(Zr0.7Sn0.24Ti0.06)O3 antiferroelectric ceramics

To find a solution to the problem that antiferroelectric materials could not be used in thick-film based uncooled infrared detectors because of their high sintering temperature, Pb0.87Ba0.1La0.02(Zr0.7Sn0.24Ti0.06)O3+6wt%PbO antiferroelectric ceramics were first prepared at 1000°C by using 0.8PbO–0.2B2O3 glass as a sintering aid. The results showed that the addition of 0.8PbO–0.2B2O3 sintering aids was beneficial for reducing the sintering temperature without deteriorating the electric properties when the content of glass was practical. The ceramics containing 1wt% 0.8PbO–0.2B2O3 sintering aids demonstrated optimal electrical field induced pyroelectric properties. The largest pyroelectric coefficient of 6100μC/m2K and figure of merit of 17×10−5Pa−0.5 were obtained in Pb0.87Ba0.1La0.02(Zr0.7Sn0.24Ti0.06)O3+6wt%PbO antiferroelectric ceramics with 1wt% glass doping, which can be comparable to that of conventional phase transition materials at a high temperature sintering. The large pyroelectric coefficient and figure of merit of low temperature sintered antiferroelectric ceramics provide a basis for antiferroelectric materials used in thick-film based infrared detectors.

High pyroelectric response of low-temperature sintered Pb0.87Ba0.1La0.02(Zr0.7Sn0.24Ti0.06)O3 antiferroelectric ceramics

Pb0.87Ba0.1La0.02(Zr0.7Sn0.24Ti0.06)O3 antiferroelectric ceramics with high pyroelectric response were first prepared at a temperature as low as 1000°C using PbO–B2O3 glass. The result showed that suitable PbO content in PbO–B2O3 glass was good for the improvement of electrical properties of antiferroelectric ceramics. Besides, it was observed that with the increase of sintering time, the AFE phase was gradual instable, which was attributed that B3+ with small ions radius replacing Ti4+ with large ions radius caused the increase of tolerance factor of antiferroelectric ceramics, and the dielectric peak became steep due to the decrease of glass content with small dielectric constant. Further, The maximum pyroelectric coefficient of 9050μC/m2K and maximum figure of merit of 20.7×10−5Pa−0.5 were obtained in Pb0.87Ba0.1La0.02(Zr0.7Sn0.24Ti0.06)O3 antiferroelectric ceramics with 1wt% 0.8PbO–0.2B2O3 glass sintered at 1000°C for 12h, which are comparable with that of phase transition pyroelectric materials BST and BZT sintered at as high as 1300°C. Our results open up the way to low-temperature sintering of PZST based antiferroelectric ceramics with high pyroelectric response and provide a basis for antiferroelectric materials used in thick-film based uncooled infrared detector.

High pyroelectric response of lead zirconate stannate titanate based antiferroelectric ceramics with low Curie temperature

With a view to solve the problem that the Curie temperature of antiferroelectric ceramics was higher than the use temperature of uncooled infrared detectors, four groups of samples with different Ba content were prepared by conventional solid state reaction process, and the effects of Ba2+ content on the ferroelectric, dielectric and electric field-induced pyroelectric properties of four groups of samples were studied. The results indicated four groups of samples showed different dielectric properties which were attributed that the first and the fourth group of samples were in FE phase and the second and the third group of samples were in AFE phase. Large pyroelectric coefficient can be obtained in all four groups of specimens near room temperature by appropriate Ba doping. The maximum pyroelectric coefficient of 13,800μC/m2K and figure of merit of 16.5×10−5Pa−0.5 at room temperature were obtained in (Pb0.97−xBaxLa0.02) (Zr0.7Ti0.05Sn0.25)O3 antiferroelectric ceramics with 0.138mol Ba content.

Dielectric and pyroelectric properties of nylon 5,7 as a function of molecular orientation

Abstract Nylon 5,7 has been made in film form with two different molecular orientations. X-ray studies show that the H-bonds in rolled and annealed Nylon 5,7 are oriented approximately perpendicular to the film surface. Because of this, the film has a low dielectric response and reasonably high pyroelectric response. In gold nucleated, directionally crystallized Nylon 5,7 the H-bonds are oriented parallel to the film surface. Such films have a high dielectric response and low pyroelectric response. This can be understood in the light of the proposed model of H-bond twinning. The disappearance of the alpha relaxation in film A was ascribed to pinning of the amorphous phase since the oriented film was annealed under tension. High temperature dielectric loss of film A follows Jonscher's power law with n close to 1 showing that it is probably due to ionic conduction. Dielectric loss in film B gives an n value of 0.30 in the temperature range of 130–160°C, indicating that much of the loss is not due to ionic c...