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In the present work, a pebble bed thermal energy storage (PBTES) system is developed to utilize the waste energy from engine exhaust. The developed PBTES is integrated with an electric dynamometer coupled stationary Diesel engine for experimental investigation. The engine performance is compared with and without integration of the PBTES system. The 60-75% of energy can be stored in the fabricated system during the charging process at various load conditions. It is found that nearly 11-15% of engine fuel energy can be saved using this storage system considering the charging process. Heat recovery/discharging from PBTES shows that 6-8.5% of fuel primary energy can be saved. The system combined (engine+PBTES) efficiency varies from 11-38% at different load conditions. The highest exergy saved is obtained as 3.32% when a 3 kW load is applied. The developed system can be easily used for domestic or industrial use space heating or hot fluid requirements.

The effect of nonstoichiometry on the pyroelectric, electrocaloric and energy storage properties in 0.94NaxBiyTiO3–0.06BaTiO3 (y = 0.49, 0.50, 0.51: x = 0.50 and y = 0.50: x = 0.51) bulk ceramics is investigated. The depolarization temperature and ferroelectric-relaxor phase transition vary with stoichiometry. The electrocaloric temperature (∆T) and entropy (∆S) change were calculated by Maxwell relation at different temperatures and electric fields. The 0.94Na0.50Bi0.49TiO3–0.06BaTiO3 showed maximum ∆T and ∆S as 1.2 K and 1.9 J/kgK, respectively at room temperature and 5.5 MV/m. However, Bi sufficient or excess compositions have the large value of ∆T (0.76 K) and ∆S (0.96 J/kgK) in the higher temperature range ~ 397–426 K. The pyroelectric coefficient obtained for stoichiometric composition is 9.4 × 10−4 C/m2K and 87 × 10−4 C/m2K at room temperature and Td, which increases to 10.1 × 10−4 C/m2K and 105 × 10−4 C/m2K, respectively for nonstoichiometric sample. The various pyroelectric figures of merit are calculated for all compositions and found that results are comparable with the previously reported lead-free ceramics. The recoverable energy storage and efficiency are enhanced by 35% (428 to 579 kJ/m3) and 21% (45% to 66%), respectively, when a nonstoichiometric composition is used. Thus, nonstoichiometry is an effective tool to tune pyroelectric, electrocaloric and other properties for the required application.

In this work, a systematic approach of waste (thermal/mechanical) energy harvesting and storage potential is studied in Ba0.85Zr0.15TiO3 (BZT) ceramics. The effect of stress on energy storage density (harvesting/storage) and electrocaloric performance is also studied. For this purpose, polarization–electric field hysteresis loops were recorded at various temperatures and uniaxial compressive stress. The Olsen cycle and electro-mechanical cycle are used for direct waste heat or mechanical energy to electrical energy conversion. A thermal energy-harvesting density of 42 kJ/m3 per cycle was obtained when the Olsen cycle was operated between 296–343 K and 0.25–1.5 MV/m. The electro-mechanical cycle-based energy harvesting is estimated as 78 kJ/m3 under the applied stress of 5–160 MPa and the electric field of 0.25–1.5 MV/m. The energy storage density is found as 39 kJ/m3 at zero stress field and 343 K, which increases to 53 kJ/m3 under the biased stress of 80 MPa in a wide operating temperature range of 296–328 K. It is observed that the high energy storage is a result of the reduction of the hysteresis loss. The electrocaloric temperature is found as 0.16 K and 0.18 K under the 0 and 80 MPa stress fields, respectively. Overall, the reported findings will enrich our understanding of the stress effect on BZT materials, which offers high performance for energy harvesting and storage-based applications. Moreover, this work can be also helpful in improving the energy storage density and electrocaloric effect via stress confinement.

BaTiO3-based derivatives have been explored in recent times for potential applications in energy harvesting and ultrasonics. To this end, energy harvesting and conversion applications require an understanding of the conduction and loss mechanisms. The conduction mechanism in Ba0.9Ca0.1TiO3 (BCT) ceramics is studied using impedance spectroscopy at different temperatures. Impedance analysis suggests the presence of two types of relaxation processes corresponding to grain and grain boundary contributions. The relaxation mechanism follows non-Debye-type behavior. The high resistance of the grain (bulk) in the ferroelectric region does not contribute to the high losses; the losses probably result from the phase transition. In addition, BCT ceramics exhibit a negative temperature coefficient of resistance (NTCR). The open-circuit pyroelectric voltage shows a twofold increase compared to (Ca, Zr) modification in BaTiO3.

The waste thermal/heat energy harvesting can contribute to more sustainable and efficient energy systems. The high energy harvesting and storage are indispensable with considering ferroelectric/antiferroelectric materials. In this work, Pb0.99Nb0.02[(Zr0.57Sn0.43)0.92Ti0.08]0.98O3 (PNZST) is studied for high energy density (harvesting and storage). The Olsen cycle is performed on the materials for direct thermal/waste heat to electrical energy conversion. A large energy harvesting density of 1.0 MJ/m3 per cycle was obtained at temperatures of 303 and 403 K, cycling the electric field between 1 and 9 kV/mm. An estimated high energy harvesting is a result of the polarization change due to the ferroelectric (rhombohedral) to antiferroelectric (tetragonal) phase transition. The high energy storage of 0.9 J/m3 and energy efficiency of 81% were obtained at 403 K under an electric field of 9 kV/mm. The results will enrich our understanding of PNZST materials that offer high-performance energy harvesting and storage-based applications. This work can also be helpful in improving energy harvesting density via phase transition behaviors.

This chapter discussed the object oriented finite element (OOF2)-based studies for ceramic composites. OOF2 is an effective method that uses an actual microstructure image of the material/composites for simulation. The effect of filler inclusions on the thermomechanical properties (coefficient of thermal expansion, thermal conductivity, Young’s modulus, stress and strain) is discussed. For this purpose, various ceramics composites (thermal barrier coating and ferroelectric based) are considered at homogeneous and heterogeneous temperature/stress conditions. The maximum stress is found at the interface of the filler/matrix due to their mismatch of thermal expansion coefficient. Further, residual and localized interface stress distributions are evaluated to analyze the composite’s failure behavior. The possible integration of OOF2 with other simulation techniques is also explored.

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.

In this study, the creep and fatigue characterization is performed for 0.5Ba(Zr[Formula: see text]Ti[Formula: see text]O[Formula: see text]0.5(Ba[Formula: see text]Ca[Formula: see text]TiO3 (BZT-BCT) bulk ferroelectric ceramics. A function generator is used to generate the required waveform of the voltage amplifier for fatigue and creep analysis. The evolution of polarization is studied for electrical creep. The effects of temperature and electric field on the electric displacement are studied. Hysteresis–butterfly loops are analyzed for fatigue tests for different thermal loads up to 106 cycles. It inheres that the material is stable below 75[Formula: see text]C and can withstand high cycle fatigue loads (25 Hz, ± 1.5 kV/mm).

This work deals with enhancing piezoelectric energy harvesting by incorporating different auxetic structures and varying geometrical parameters. A bimorph consisting of polyvinylidene fluoride as a piezoelectric layer and brass auxetic substrate (re-entrant, s-shape, and elliptical holes) are considered for analysis. A finite element method-based simulation is performed to find the best auxetic systems that provide higher power output. The environmental vibration is taken for energy harvesting; thus, the first resonance frequency is below 100 Hz. The maximum power of ∼0.52, ∼0.67, and ∼0.79 mW is estimated for piezoelectric energy harvesters (PEH’s) re-entrant, s-shape, and elliptical holes. The auxetic re-entrant, s-shape, and elliptical substrate-based PEHs show 200%, 300%, and 333% more power than the solid substrate (conventional design). However, the elliptical-based auxetic structure obtains a maximum power density of 0.004 66 mW/mm3. The stresses in all structures are within the permissible limit; hence, any design can be used for practical applications. All three auxetics have comparable geometrical dimensions and the same material is used; thus, auxetic behavior is independent of the material employed and depends on the structure’s shape. The estimated power is higher than that reported in the literature.

The energy harvesting potential in bulk lead-free Ba0.85Ca0.15 Ti0.9−xSnxZr0.10O3 (BCT–BZT-Sn) ferroelectric ceramic has been investigated. All the compositions (x = 0.01, 0.02, 0.04, and 0.06) were fabricated by the solid-state reaction route and possessed a single-phase perovskite structure, whereas a small amount of secondary phase was observed in the x = 0.06 sample. The Olsen cycle was used to estimate the enhanced thermal energy harvesting performance over a wide range of temperatures and electric field strengths. The energy conversion density increases up to x = 0.02 and decreases thereafter owing to a reduction in the hysteresis loop area. The maximum energy conversion density for the BCT–BZT-Sn composition were found to be 306 kJ/m3, 332 kJ/m3, 226 kJ/m3 and 167.6 kJ/m3 for x = 0.01, 0.02, 0.04 and 0.06, respectively, for a temperature range of 303–373 K and an electric field of 1–29 kV/cm. These values are three times higher than that of the soft PbZrTiO3 which has an almost equivalent piezoelectric performance as Ba0.85Ca0.15Ti0.9Zr0.10O3 at room temperature. The obtained energy conversion is also higher than most other lead-based and lead-free ferroelectric bulk materials.

This work studies temperature dependent dynamics hysteresis scaling of Ba0.85Ca0.15Ti0.9–xSnxZr0.10O3 (BCT-BZT-Sn) bulk ferroelectric ceramics. The scaling relation are derived for coercive...

In this work, multi-layer ceramics (MLC) are fabricated for vibrational energy harvesting using 0.5 mol.% CuO added 0.69Pb(Zr0.47Ti0.53)O3-0.31Pb(Zn0.4Ni0.6)1/3Nb2/3O3 (0.5CPZT-PZNN). 0.5CPZT-PZNN has a high transduction coefficient of 20,367 m2/N with a high Curie temperature of 300°C. The effect of the number of layers (n-layers = 1, 3, 5 and 7) on the active power density is systematically investigated. MLC-based piezoelectric energy harvesting (PEH) can increase the active power output by approximately 2.5 times as compared to bulk PEH (n = 1). For the bulk ceramic, PEH active power density is found to be 21 mW/cm3 , whereas maximum active power density is obtained for n = 5 (49.7 mW/cm3). However, upon increasing layers (n = 7), active power density is decreased due to high capacitance. The result shows that the MLC-based PEH can increase output current/voltage and decrease the matching resistive load. In addition, effect of the load resistance on the voltage, current and active power density is also discussed. Finally, a comparison of various piezoelectric material based power output in MLC-system has been also presented.

Candle soot, traditionally considered as an unwanted source of air-pollution, has slowly been phased out by modern lighting techniques. However, a 2007 study by Liu and co-workers first brought to light the presence of fluorescent carbon nanoparticles (CNPs) in untreated candle-soot (CS). Subsequent studies revealed that these soot-generated CNPs can be refined and extracted for various applications including humidity sensing, trace element detection and biomedical to Li-ion batteries, supercapacitors, electrocatalysis and solar collector among others. There are over 100 published articles dealing with fabrication, extraction, treatment and application of CS derived CNPs. However, unlike traditional carbon-based nanostructures including graphene and fullerene, this field lacks the presence of a systematic endeavour to tap into the vast potential of candle-soot. Therefore, this article aims to present a focused review on the topic of CS derived CNPs and their potential applications. The paper starts with a brief introduction on the topic of candle-soot and its historic significance. This is followed by a description of the techniques used to extract, refine and functionalize these carbon particles. Thereafter the reported applications of candle-soot derived nanostructures and their comparative analysis with the current state-of-art are provided. Finally, a section discussing future scopes and challenges is presented followed by conclusions.

In the present work, the pyroelectric performance of [Bi0.48Na0.4032K0.0768]Sr0.04(Ti0.975Nb0.025)O3 (BNT-2.5Nb) ceramics is investigated. At room temperature, the value of pyroelectric coefficient found as 13.2 × 10−4 C/m2 K which is higher than many lead-free ferroelectric materials. Further, the pyroelectric figures of merit (FOMs) for detectivity (Fd), voltage responsivity (Fv), current responsivity (Fi), and energy harvesting (Fe*) are calculated. BNT-2.5Nb ceramics show pyroelectric open circuit voltage as 0.45 V when it was exposed to temporal temperature gradient. This work result indicates that the Nb-doping in Bi0.5Na0.5TiO3-based composition can be beneficial for lead-free pyroelectric device applications.

In this article, we focus on cement-binded Ba0.85Sr0.15Zr0.1Ti0.9O3 ceramics for pyroelectric applications. It was prepared with the Ba0.85Sr0.15Zr0.1Ti0.9O3-to-cement ratios of 85%:15% and 80%:20% by weight. In order to improve the effectiveness of thermal-to-electric energy conversion, the synchronized switch harvesting on inductor technique is experimentally tested on cement composites. Our experimental findings reveal that this concept based on synchronized switch harvesting on inductor can significantly increase the amount of power extracted from pyroelectric materials. Furthermore, the optimized power across 15% and 20% cement composites were found to be 7.2 and 6 nW, respectively, in series synchronized switch harvesting on inductor and 8.5 and 7 nW, respectively, in parallel synchronized switch harvesting on inductor. These values are significantly higher when compared with non-switched circuit for pyroelectric applications. Although, from the obtained results for the prepared composites, the power output is less when compared with pure Ba0.85Sr0.15Zr0.1Ti0.9O3, they have some advantages: these composites can be made without any sintering process and are compatible for structural applications.

PbVO3 features giant tetragonal distortion (c/a = 1.23) and spontaneous polarization (Ps = 101 μC/cm2) originating from the ordering of dxy orbital of V4+ with single d electrons. A dedicated study of Cr-substituted PbVO3 prepared by high-pressure synthesis afforded a well-defined variation in c/a ratio. Ensuing changes in atomic structure were correlated to ferroelastic domain switching and a temperature-induced structural transition to a cubic phase accompanied with an insulator-to-metal transition and a negative thermal expansion.

Ferroelectric materials have great potential use for solid-state refrigeration. However, their working temperature is restricted to Curie temperature; the working temperature can be increased by the new component of strain gradient-driven caloric effect or flexocaloric effect (FCE). The FCE relies on the inhomogeneous strain of the crystal lattice to induce polarization in centrosymmetric crystals (flexoelectricity). The strain gradient-induced polarization is defined by flexoelectric polarization coefficient and is utilized to estimate the FCE. As the FCE is a relatively new phenomenon, several ways can be used to calculate it. Different methods of flexocaloric quantification in ferroelectric materials (Pb(Mg1/3Nb2/3)O3 and Ba0.67Sr0.33TiO3) are discussed in the present work. The FCE can be obtained based on the measured properties and combination between the polarization and strain. This allows one to study the actual or net flexocaloric behavior in the material. It was found that the quantification of temperature change varies according to the method used for estimation. The experimental confirmation is required for validation of the proposed methods of estimation. Further, this work also discusses the possibility of other ways that are untouched by the research community. The analysis indicates a substantial untapped potential for solid-state refrigeration and warrants further research.

In the present work, pyroelectric energy harvesting potential in 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Sr0.3)TiO3 (BZT-BST) ceramics is studied. The pyroelectric coefficient was obtained by the Byer–Roundy method. The pyroelectric figures of merit for energy harvesting applications are also estimated. The pyroelectric performance in terms of measuring voltage is obtained by subjecting the material to thermal fluctuations. To increase the energy harvesting potential from waste thermal/heat energy to electrical energy, the synchronized switch harvesting on inductor (SSHI) method is used. The SSHI technique findings reveal that this concept can considerably enhance the amount of power extracted from the pyroelectric materials.

This work contributes towards the analysis of the pyroelectric behaviour of lead-free pyroelectric 0.5Ba (Zr0.2Ti0.8)O3-0.5(Ba0.7Sr0.3)TiO3 (BZT-BST) ceramics. The pyroelectric coefficient (3.4×10−4 Cm−2 K−1 at 303 K) was obtained by the Byer-Roundy method. The pyroelectric figures of merit for current, voltage, detectivity and energy harvesting applications are discussed with respect to possible optimization of these parameters.All the above mentioned figures of merit are dependent on the permittivity and dielectric loss. Hence, impedance analysis was conducted to identify the dominant contributions in permittivity and dielectric loss. The activation energies for bulk and grain boundary are ~1.0 eV and ~1.2 eV, respectively, which indicates presence of mobile oxygen vacancies. The contribution of these processes to the dielectric loss in the temperature range of interest (300–340 K) is, however, very low. The permittivity and the dielectric loss are dominated by a strictly dielectric response resulting from the phase transition in the respective temperature range.

New lead-free tetragonal perovskites Na1/2Bi1/2VO3 and K1/2Bi1/2VO3 were synthesized under high pressure (6 GPa) and high temperature (1473 K), based on the design of materials optimizing the lone pair effect of the A-site ion and utilizing the Jahn–Teller effect in the B-site V4+. The magnitudes of the c/a ratio and spontaneous polarization, PS, were 1.085 and 108 μC/cm2, respectively (73 μC/cm2 by the point charge model), for Na1/2Bi1/2VO3 and 1.054 and 92 μC/cm2, respectively (56 μC/cm2 by the point charge model), for K1/2Bi1/2VO3, which are comparable to the well-known lead-based ferroelectric PbTiO3. This approach can guide the design of new lead-free ferroelectric and piezoelectric materials.

(1-x)(Ba0.9Ca0.1)TiO3-xBa(Sn0.2Ti0.8)O3 ceramics x = 0, 0.4, 0.5 and 0.6 were synthesized. With Sn addition, orthorhombic to tetragonal transition temperature increased to higher temperature side and tetragonal to cubic transition temperature reduced towards room temperature for x = 0.4 and x = 0.5 and all phase transitions merged into one for x = 0.6. Multiple heating-cooling cycles' measurement of pyroelectric current was carried out over an excursion of temperature relevant to the pyroelectric applications. The pyroelectric coefficient increased from 1 × 10−4C/m2.K (x = 0) to 2.05 × 10−4C/m2.K (x = 0.4) sample at 303 K. Such enhancements could prove to be advantageous in deriving pyroelectric figures of merit. © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

We have synthesized Ba0.85Ca0.15Zr0.10Ti0.88Sn0.02O3 (BCZT-Sn)-cement composites. They were prepared as BCZT-Sn to cement ratios of 90–10% and 85–15% by weight. The larger fraction of BCZT-Sn ceramic was used to minimize the losses in the composites. The open circuit voltage was found to be 0.75 V, 0.56 V and 0.4 V for pure, 10% and 15% cement composites, respectively. The voltage and current were also measured across resistances of 1 and 3 MΩ, and the obtained voltages were lower for composites compared to pure BCZT-Sn. Nonetheless, they remain promising candidates over traditional pyroelectric materials for device applications owing to their advantages, such as (1) these composites can be made without any sintering process and (2) they can be made in any shape and size. We also studied relative permittivity, which influences performance of pyroelectric devices.

The review describes the development and advancement of thermoelectric based dehumidifier systems. Thermoelectric cooling in thermoelectric dehumidifiers has various advantages over conventional techniques, such as lightweight, compact size, noise-free (no moving part), and eco-friendly operation. The review initially describes the basic principle and different techniques used for dehumidification. Then, thermoelectric dehumidifiers are introduced and their governing parameters are discussed. Further, thermoelectric dehumidifier-based prototypes are reviewed and discussed over their design and performance. The patents and commercialized products developed on thermoelectric dehumidifiers were also briefly discussed and compared. Lastly, this review states the challenges for the more efficient and large-scale operation of thermoelectric-based dehumidifiers and simplifies ways for further improvement. Thus, the study illustrates the current status of thermoelectric dehumidifiers and provides futuristic scopes for their development.

Present work shows waste energy (thermal/mechanical) harvesting and storage capacity in bulk lead-free ferroelectric 0.6Ba(Zr0.2Ti0.8)O3–0.4(Ba0.7Ca0.3)TiO3 (0.6BZT-0.4BCT) ceramics. The thermal energy harvesting is obtained by employing the Olsen cycle under different stress biasing, whereas mechanical energy harvesting calculated using the thermo-mechanical cycle at various temperature biasing. To estimate the energy harvesting polarization-electric field loops were measured as a function of stress and temperatures. The maximum thermal energy harvesting is obtained equal to 158 kJ/m3 when the Olsen cycle operated as 25–81 °C (at contact stress of 5 MPa) and 0.25–2 kV/mm. On the other hand, maximum mechanical energy harvesting is calculated as 158 kJ/m3 when the cycle operated as 5–160 MPa (at a constant temperature of 25 °C) and 0.25–2 kV/mm. It is found that the stress and temperature biasing are not beneficial for thermal and mechanical energy harvesting. Further, a hybrid cycle, where both stress and temperature are varied, is also studied to obtain enhanced energy harvesting. The improved energy conversion potential is equal to 221 kJ/m3 when the cycle operated as 25–81 °C, 5–160 MPa and 0.25–2 kV/mm. The energy storage density varies from 43 to 66 kJ/m3 (increase in temperature: 25–81 °C) and 43–80 kJ/m3 (increase in stress: 5–160 MPa). Also, the pre-stress can be easily implemented on the materials, which improves energy storage density almost 100% by stress induced domain switching. The results show that stress confinement can be used to enhance energy storage effectively.

This article presents electrocaloric effect in BaxSr1-xTiO3 ferroelectric ceramics using an indirect approach based on Maxwell’s relations. The peak electrocaloric performance is found to be an adiabatic temperature change of 0.67, 0.83, and 0.61 K and isothermal entropy change of 0.9, 1, and 0.7 J/kg.K for x = 0.7, 0.8, and 0.9, respectively, under an electric field of 33 kV/cm. The electrocaloric coefficient of performance (COP) of materials were also estimated as 17, 5.47, and 5.68 when x = 0.7, 0.8, and 0.9, respectively, in BaxSr1-xTiO3 at 33 kV/cm (303 K). Further, the ferroelectric hysteresis parameters scaling relations of coercive field (E c) and remnant polarization (P r) as a function of temperature have been estimated. The back switching polarization (P bc) as a function of temperature (T) was estimated by the Arrhenius law in order to understand the domain dynamics, and the average activation energy was evaluated.

When employed appropriately, ferroelectric materials present themselves as one of the most efficient means of waste (thermal/mechanical) energy scavenging. A large conversion potential can be obtained when appropriate materials are combined with high-field actuation (Ericsson cycle). However, waste energy rarely presents itself in an isolated form (heat or vibration). There is also a distinct lack of systems capable of simultaneous thermomechanical energy conversion, especially in the low-frequency range. In this regard a systematic approach to the concept of combined energy harvesting and storage potential of a singular material system is presented. Polarization versus electric field hysteresis loops were gathered as a function of temperature, uniaxial compressive stress, and electric field. Thereafter, a theoretical assessment was made to the effect of the biased and unbiased energy conversion potential of 0.50Ba(Zr0.2Ti0.8)O3– 0.50(Ba0.7Ca0.3)TiO3 bulk lead-free ferroelectric material. Maximum energy conversion potentials of 150 and 210 kJm@3 were obtained for thermal (5 MPa, 24–96 8C) and mechanical cycles (24 8C, 5–160 MPa), respectively. A slightly improved performance of 220 kJm@3 was obtained under simultaneous depolarization, despite performance degradation through individual biasing. However, the energy-storage density improved by 100% (80 kJm@3) and 50% (60 kJm@3), respectively, when operated under elevated stress (60 MPa) and temperature (90 8C). Results are indicative of a singular material system that could be used for combined thermomechanical energy conversion and on-board storage capacity.

In the present work, the pyroelectric properties of Sn-doped BaTiO3 (BaTi1-xSnxO3) were investigated. A significant increase in pyroelectric coefficient was observed for x = 0.05 composition and found to be 10 × 10−4 C/m2 K at 350 K. Further, the pyroelectric figure of merits (FOMs) for current responsivity (Fi), voltage responsivity (Fv), and energy harvesting (Fe and Fe∗) were calculated for all investigated samples. A large improvement in FOMs was achieved for x = 0.05 compared with undoped ceramic. BaTi1-xSnxO3 (x = 0.05) was subjected to further pyroelectric analysis revealing an open-circuit voltage of 0.6 V when it was exposed to temporal temperature gradient. The voltage and current were also measured across resistances 100 kΩ, 1 MΩ, and 5 MΩ. The results reveal that BaTi0.95Sn0.05O3 will be one of the potential lead-free pyroelectric materials.

The 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 Cm^-2K^-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.

Flexoelectric effect is acquiring increased attention owing to its potential advantages towards sensor/transducer applications. Flexoelectricity can be employed to raise the functional working temperature of most ferroelectric devices beyond Curie temperature. Few recent studies have claimed significant (flexoelectric) piezoelectric performance above Curie temperature. However, little effort has been made to develop the pyroelectric capabilities of such materials. This paper aims to highlight the pyro-paraelectric (pyroelectric above Curie temperature) attributes of multiple ferroelectric systems, under the influence of inhomogeneous strain. Furthermore, cantilever shaped system is optimised for enhanced pyroelectric performance to generate a large output signal, in a wide temperature range.

Ferroelectric materials are being actively explored for next-generation solid-state cooling technology. Even though bulk materials possess an advantage in terms of overall heat extraction capacity, their performance is limited due to low adiabatic temperature change. In this regard, the present article explores enhanced cooling capacity of bulk polycrystalline Pb0.99Nb0.02(Zr0.95Ti0.05)0.08O3 (PNZT) through external-field mediation and coupled caloric effects. Barocaloric (BC) and electrocaloric (EC) effects were indirectly estimated using polarization versus electric field (P-E) loops (under varying pressure and temperature). It was observed that under applied pressure of 325 MPa, ∆TEC could be improved from 1 K to 4.5 K. Similarly, a peak unbiased ∆TBC of 1.5 K could be enhanced to 5.3 K under an electric field of 5 MV.m−1. These figures correspond to an improvement of ~400% over the unbiased values. The results are indicative of the potential of multicaloric cooling capacity of bulk ferroelectric materials. This article is protected by copyright. All rights reserved.

In the present study, 3BaO-3TiO2-B2O3 (BTBO) glass-added 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (BNT-BT) ferroelectric ceramics were synthesized using a conventional solid-state reaction methodology. The electrocaloric effect on glass-added ceramics was calculated using Maxwell relations. The maximum adiabatic temperature changes of 0.21, 0.25, and 0.14 K were obtained at 40 kV/cm for 2, 4, and 6% glass addition which are significantly higher than those of the pure sample (0.08 K) under study. The results reveal that glass addition up to 4% resulted in enhanced electrocaloric response. Further, the effect of glass addition on the dielectric properties was investigated. The dielectric constant decreases with glass addition compared with pure BNT-BT at 303 K.

Solid state refrigeration based on ferroelectric materials can potentially be competing in not-in-kind refrigeration technology. However, their functionality is currently limited to Curie temperatures. Through this article, authors have attempted to describe an unexplored component of the stress-driven caloric effect, obtainable beyond the Curie point. The phenomenon, termed as the flexocaloric effect (FCE), relies on inhomogeneous straining of the crystal lattice to induce polarization in centrosymmetric crystals (flexoelectricity). For this study, a truncated pyramid geometry was selected, and the dependence of sample height on caloric capacity was studied. A peak temperature change of 1.75 K (313 K) was estimated for Ba0.67Sr0.33TiO3 (BST) ceramics employing a truncated pyramid configuration.

In this work, zinc oxide (ZnO) nanowire is proposed for elastocaloric application which has been overlooked until now. The elastocaloric effect ([Formula: see text]CE) is calculated by Maxwell relation. The large elastocaloric temperature and entropy change evaluated as 17 K and 28 J/kgK, respectively, at 300 K correspond to the stress of 12 GPa or strain of 5.5% by the simulation data. The elastocaloric temperature can be increased to 22 K under the operating tempering of 600 K. However, [Formula: see text]CE estimated from the experimental data is found as 2.6 K at 300 K, which corresponds to stress of 6 GPa. These results are expected to significantly expand the knowledge of ZnO nanomaterials as a potential candidate for [Formula: see text]CE. The results are based on the indirect approximation; hence, a direct measurement is needed to verify the obtained results.

Flexocaloric and elastocaloric effect are investigated in a 0.66Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 single crystal. The maximum flexocaloric temperature (0.43 K) and entropy (0.38 J/kg K) change are obtained at Curie temperature under a strain gradient of 5000 m−1. A peak elastocaloric temperature (1.45 K) and entropy (1.33 J/kg K) change due to strain gradient is evaluated at the Curie temperature under the applied stress of 250 MPa. 0.66Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 encompasses an enormous elastic contribution to the flexocaloric effect instead of the polarization at similar stress level. The formulation used for caloric calculation is based on strong approximation and available data; therefore, further research is warranted to validate this work.

In this work, effect of sintering temperature (1400–1500°C) and dwell time (3–6hr) on the ferroelectric properties are investigated for Ba0.85Ca0.075Sr0.075Ti0.90Zr0.10O3 (BCSTZO) ceramics. The fer...