Search

Multiple caloric effects have been investigated for Fe-doped bulk (Ba0.865Ca0.135Zr0.1089Ti0.8811Fe0.01)O3 (BCZTO-Fe) ferroelectric ceramic. Indirect predictions were made using Maxwell's relations in conjunction with data from experimental observations. It was revealed that bulk BCZTO-Fe has huge untapped potential for solid-state refrigeration. A peak electrocaloric effect of 0.45 K (347 K) was predicted for 0–3 kV.mm−1 electric field, significantly higher than other BCZTO based materials. A maximum elastocaloric cooling of 1.4 K (298 K) was achieved for applied stress of 0–200 MPa. Finally, an unforeseen component of electric field driven caloric effect has been reported as inverse piezocaloric effect, with a maximum temperature change of 0.28 K (298 K).

The present work aims to investigate the phase transition, dispersion and diffusion behavior of nanocomposites of carbon nanotube (CNT) and straight chain alkanes. These materials are potential candidates for organic phase change materials(PCMs) and have attracted flurry of research recently. Accurate experimental evaluation of the mass, thermal and transport properties of such composites is both difficult as well as economically taxing. Additionally it is crucial to understand the factors that results in modification or enhancement of their characteristic at atomic or molecular level. Classical molecular dynamics approach has been extended to elucidate the same. Bulk atomistic models have been generated and subjected to rigorous multistage equilibration. To reaffirm the approach, both canonical and constant-temperature, constant- pressure ensembles were employed to simulate the models under consideration. Explicit determination of kinetic, potential, non-bond and total energy assisted in understanding the enhanced thermal and transport property of the nanocomposites from molecular point of view. Crucial parameters including mean square displacement and simulated self diffusion coefficient precisely define the balance of the thermodynamic and hydrodynamic interactions. Radial distribution function also reflected the density variation, strength and mobility of the nanocomposites. It is expected that CNT functionalization could improve the dispersion within n-alkane matrix. This would further ameliorate the mass and thermal properties of the composite. Additionally, the determined density was in good agreement with experimental data. Thus, molecular dynamics can be utilized as a high throughput technique for theoretical investigation of nanocomposites PCMs.

Elastocaloric effect has been experimentally demonstrated in bulk (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 polycrystalline ferroelectric material. Predictions were made using Maxwell's relationship for elastocaloric effect. A maximum elastocaloric effect of 1.55 K was observed for an initial material temperature of 340 K and applied compressive stress of 0–250 MPa (under a constant electric field of 2 MV m−1). The reported value is several times larger than the peak electrocaloric effect for the same material. The results indicate that ferroelectric materials possess a huge potential for elastocaloric refrigeration.

This paper examines the selection and performance evaluation of a variety of piezoelectric materials for cantilever-based sensor applications. The finite element analysis method is implemented to evaluate the relative importance of materials properties such as Young's Modulus (E), piezoelectric stress constants (e31), dielectric constant (ε) and Poisson's ratio (υ) for cantilever-based sensor applications. An analytic hierarchy process (AHP) is used to assign weights to the properties that are studied for the sensor structure under study. A technique for order preference by similarity to ideal solution (TOPSIS) is used to rank the performance of the piezoelectric materials in the context of sensor voltage outputs. The ranking achieved by the TOPSIS analysis is in good agreement with the results obtained from finite element method simulation. The numerical simulations show that K 0.5 Na 0.5 NbO 3– LiSbO 3 (KNN–LS) materials family is important for sensor application. Young's modulus (E) is most influencing material's property followed by piezoelectric constant (e31), dielectric constant (ε) and Poisson's ratio (υ) for cantilever-based piezoelectric sensor applications.

Ferroelectrics form an important class of materials and are employed for a variety of applications. However, specific applications dictate the need of tailored ferroelectric response. This creates a requirement to obtain ferroelectric materials with tunable properties. Generally, chemical modifications or domain engineering are employed to this effect. This study attempts to shed light on the use of compressive pre-stresses for tuning and enhancing the ferroelectric properties. For the purpose, polarization versus electric field hysteresis data for 68Pb(Mn1/3Nb2/3)O3-32PbTiO3 (PMN-PT) single crystals were obtained as a function of uniaxial compressive stresses and operating temperatures. These data were utilized to investigate the effects of mechanical confinement for four individual case studies of electrocaloric effect, electrical energy storage, pyroelectric, and piezoelectric effect. A significant improvement was obtained for all case studies. The adiabatic temperature change was improved by ≈80% (28 ...

Temperature dependent dynamic hysteresis of 0.715Bi0.5Na0.5TiO3-0.065BaTiO3-0.22SrTiO3 (BNT-BT-ST) bulk ferroelectric ceramic was systematically studied. The scaling relations were estimated for corrective electric field remnant polarization and hysteresis loop area as a function of temperature It was observed that and for a constant magnitude of electric field To understand the domain dynamics, back-switching polarization as a function of is also predicted. The relation between back-switching polarization and temperature is estimated by well described Arrhenius law to evaluate the average activation energy. It also depends on the applied electric field; the relation fits well to a simple exponential decay function. The saturation polarization as a function of was also evaluated to estimate the electrocaloric effect. It was found that electrocaloric effect and heat extract capacity in BNT-BT-ST ceramic is of a similar order to that observed in most other lead-free bulk ferroelectric ceramics. It can be said that BNT-BT-ST is also a promising material for solid state refrigeration. These results can be helpful to understand the temperature dependent hysteresis behavior and polarization switching in lead-free ferroelectric ceramics.

Correction for ‘Pyroelectric materials and devices for energy harvesting applications’ by C. R. Bowen et al., Energy Environ. Sci., 2014, 7, 3836–3856.

Capacitors form an indispensable part of many modern electrical and electronic devices. An ideal capacitor is expected to possess high power and energy density along with enhanced energy recovery characteristics. Anti-ferroelectric materials form a suitable candidate for ceramic-based capacitor applications, owing to their low loss and high energy density. However, these materials show ample room for improvement through physical means. In this regard, the present work deals with mechanical tuning of the energy storage density and recoverable efficiency in known anti-ferroelectric materials. For this study, various configurations of (Pb1?xLax)(Zr0.90Ti0.10)1?x/4O3 (PLZTx) ceramics have been investigated. Both mechanical confinement and temperature applications have been shown to improve the performance characteristics of all selected compositions. This behavior has been explained on the basis of competing ferroelectric and ferroelastic domain rotations. The application of suitable stress/temperature reduces hysteresis losses and delays anti-ferroelectric???ferroelectric phase transformation, which increases the electrical energy storage capacity of these materials. Mechanical confinement was observed to provide an increase in energy storage density and efficiency by approximately 38% and 25%, respectively, for the PLZT4 composition. The highest recoverable energy density of 698 m J cm?3 was achieved under compressive stress of a 100 MPa and 60 kV cm?1 applied electric field.

This work emphasis on the competence of (100)-oriented PMN–PT buffer layered (0.68PbMg1/3Nb2/3O3–0.32PbTiO3 with Pb(Zr0.3Ti0.7)O3/PbOx buffer layer) and (001)-oriented PMN–PT (0.67PbMg1/3Nb2/3O3–0.33PbTiO3) for low grade thermal energy harvesting using Olsen cycle. Our analysis (based on well-reported experiments in literature) reveals that these films show colossal energy harnessing possibility. Both the films are found to have maximum harnessable energy densities (PMN–PT buffer layered: 8 MJ/m3; PMN–PT: 6.5 MJ/m3) in identical ambient conditions of 30–150°C and 0–600 kV/cm. This energy harnessing plausibility is found to be nearly five times higher than the previously reported values to date.

This work emphasis on the competence of (100)-oriented PMN–PT buffer layered (0.68 PbMg 1/3 Nb 2/3 O 3–0.32 PbTiO 3 with Pb ( Zr 0.3 Ti 0.7) O 3/ PbO x buffer layer) and (001)-oriented PMN–PT (0.67 PbMg 1/3 Nb 2/3 O 3–0.33 PbTiO 3) for low grade thermal energy harvesting using Olsen cycle. Our analysis (based on well-reported experiments in literature) reveals that these films show colossal energy harnessing possibility. Both the films are found to have maximum harnessable energy densities (PMN–PT buffer layered: 8 MJ/m3; PMN–PT: 6.5 MJ/m3) in identical ambient conditions of 30–150°C and 0–600 kV/cm. This energy harnessing plausibility is found to be nearly five times higher than the previously reported values to date.

With the advent of modern power electronics, embedded circuits and non-conventional energy harvesting, the need for high performance capacitors is bound to become indispensible. The current state-of-art employs ferroelectric ceramics and linear dielectrics for solid state capacitance. However, lead-free ferroelectric ceramics propose to offer significant improvement in the field of electrical energy storage owing to their high discharge efficiency and energy storage density. In this regards, the authors have investigated the effects of compressive stress as a means of improving the energy storage density of lead-free ferroelectric ceramics. The energy storage density of 0.91(Bi0.5Na0.5)TiO3-0.07BaTiO3-0.02(K0.5Na0.5)NbO3 ferroelectric bulk ceramic was analyzed as a function of varying levels of compressive stress and operational temperature .It was observed that a peak energy density of 387 mJ.cm-3 was obtained at 100 MPa applied stress (25oC). While a maximum energy density of 568 mJ.cm-3 was obtained for the same stress at 80oC. These values are indicative of a significant, 25% and 84%, improvement in the value of stored energy compared to an unloaded material. Additionally, material's discharge efficiency has also been discussed as a function of operational parameters. The observed phenomenon has been explained on the basis of field induced structural transition and competitive domain switching theory.

Water-soluble and fluorescent Graphene oxide (GO) is biocompatible, easy, and economical to synthesize. Interestingly, GO is also capable of quenching fluorescence. On the basis of its fluorescence and quenching abilities, GO has been reported to serve as an energy acceptor in a fluorescence resonance energy transfer (FRET) sensor. GO-based FRET biosensors have been widely reported for sensing of proteins, nucleic acid, ATP (Adenosine triphosphate), etc. GO complexes with fluorescent dyes and enzymes have been used to sense metal ions. Graphene derivatives have been used for sensing endocrine-disrupting chemicals like bisphenols and chlorophenols with high sensitivity and good reproducibility. On this basis, a novel GO based fluorescent sensor has been successfully designed to detect estriol with remarkable selectivity and sensitivity. Estriol is one of the three estrogens in women and is considered to be medically important. Estriol content of maternal urine or plasma acts as an important screening marke...

Energy harvesting is one of the emerging applications of piezoelectric materials. In order to replace conventional lead-based materials with lead-free materials, it is important to evaluate their performance for such applications. In the present study, finite element method-based simulation shows mean power density produced from ( K 0.475 Na 0.475 Li 0.05)( Nb 0.92 Ta 0.05 Sb 0.03) O 3 add with 0.4 wt.% CeO 2 and 0.4 wt.% MnO 2 (KNLNTS) bimorph is 96.64% of lead zirconate titanate ( Pb [ Zr x Ti 1-x] O 3) (PZT) ceramics. Load resistance (R), length of proof mass (Lm) and thickness of host layer (th) are optimized (using genetic algorithm) for maximum power density and tuning the operating frequency range which is near to natural frequency of the structure. The lead-free piezoelectric material KNLNTS has comparable results to that of PZT for piezoelectric energy harvester in the ambient frequency range of 90 Hz to 110 Hz. Results show that KNLNTS ceramics can be potentially used in energy harvesting devices.

Ferroelectric materials are used in a number of applications ranging from simple sensors and actuators to ferroelectric random access memories (FRAMs), transducers, health monitoring system and microelectronics. The multiphysical coupling ability possessed by these materials has been established to be useful for energy harvesting applications. However, conventional energy harvesting techniques employing ferroelectric materials possess low energy density. This has prevented the successful commercialization of ferroelectric based energy harvesting systems. In this context, the present study aims at proposing a novel approach for enhanced energy harvesting using commercially available ferroelectric materials. This technique was simulated to be used for two commercially available piezoelectric materials namely PKI-552 and APCI-840, soft and hard lead-zirconate-titanate (PZT) pervoskite ceramics, respectively. It was observed that a maximum energy density of 348 kJm−3cycle−1 can be obtained for cycle parameters of (0–1 ton compressive stress and 1–25 kV.cm−1 electric field) using APCI-840. The reported energy density is several hundred times larger than the maximum energy density reported in the literature for vibration harvesting systems.

Object oriented finite element analysis (OOF2) is used to estimate the thermal and mechanical properties of WC– Al 2 O 3 composites. In the present work, five compositions of 10%, 20%, 30%, 40% and 50% Al 2 O 3 (by volume) are studied. Young's modulus, thermal conductivity and thermal expansion coefficient are estimated using OOF2 and compared with other known analytical methods. Stress and strain contours are plotted to study the thermal and mechanical behavior of composites. It is found that the stresses are largely concentrated at the interfaces of the WC– Al 2 O 3 phases.

Ferroelectric materials are widely employed as piezoelectric materials for numerous energy harvesting systems. However, conventional systems employing direct piezoelectric effect for vibrational energy harvesting suffer from low energy density and high actuation frequency requirements. In this regards, the authors have presented a new technique for giant mechanical energy conversion using ferroelectric/antiferroelectric materials in a cyclic manner. The proposed method will allow for large electromechanical energy conversion in a wide frequency domain. The cycle was simulated for polycrystalline Pb0.99Nb0.02[(Zr0.57Sn0.43)0.94Ti0.06]0.98O3 (PNZST) antiferroelectric bulk ceramic. It was observed that for cycle parameters of (20 to 60 kV·cm−1 and 0 to 250 MPa), a harvesting energy density of 689 kJ·m−3·cycle−1 can be obtained for uniaxial compressive stress. While an energy density of 919 kJ·m−3·cycle−1 can be obtained for radial compressive stress with cycle parameters of (20 to 60 kV·cm−1 and 0 to 360 MPa). This is several orders of magnitude larger than the highest energy density reported in the literature.

This work propounds the competence of epitaxial multiferroic thin-film heterostructures for low-grade thermal energy harvesting using Olsen cycle and ultra-high density capacitor applications. Our investigation (based on well-reported experiments in the literature) reveals that this class of materials shows a giant energy storage density as well as colossal energy harnessing possibilities. Indeed, the energy storage capability of these films is found to be 1.6 times the already existing giant value (alkali free glasses: 35 MJ m−3). On the other hand, the energy harnessing plausibility is found to be four orders of magnitude higher than the reported values to date.

This article demonstrates the colossal energy harvesting capability of a lead-free (Bi0.5Na0.5)0.915-(Bi0.5K0.5)0.05Ba0.02Sr0.015TiO3 ceramic using the Olsen cycle. The maximum harvestable energy density estimated for this system is found to be 1523 J/L (1523 kJ/m3) where the results are presented for extreme ambient conditions of 20–160 °C and electric fields of 0.1–4 MV/m. This estimated energy density is 1.7 times higher than the maximum reported to date for the lanthanum-doped lead zirconate titanate (thin film) system. Moreover, this study introduces a generalized and effective solid state refrigeration cycle in contrast to the ferroelectric Ericson refrigeration cycle. The cycle is based on a temperature induced polarization change on application of an unipolar electric field to ferroelectric ceramics.

X-ray powder diffraction along with differential thermal analysis carried out on the as-quenched samples in the 3BaO–3TiO2–B2O3 system confirmed their amorphous and glassy nature, respectively. The dielectric constants in the 1 kHz–1 MHz frequency range were measured as a function of temperature (323–748 K). The dielectric constant and loss were found to be frequency independent in the 323–473 K temperature range. The temperature coefficient of dielectric constant was estimated using Havinga’s formula and found to be 16 ppm K−1. The electrical relaxation was rationalized using the electric modulus formalism. The dielectric constant and loss were 17±0.5 and 0.005±0.001, respectively at 323 K in the 1 kHz–1 MHz frequency range which may be of considerable interest to capacitor industry.

The online version of the original article can be found at http://dx.doi.org/10.1007/s12034-009-0056-2

Transparent SrLiB9O15 (SLBO) glasses were fabricated via the conventional melt-quenching technique. X-ray powder diffraction and differential thermal analysis carried out on the as-quenched samples confirmed their amorphous and glassy nature, respectively. The dielectric constants in the 100 Hz to 10 MHz frequency range for SLBO glasses were measured as a function of temperature (300–1023 K). The dielectric relaxation characteristics were rationalized using the electric modulus formalism. The electrode polarization effect was subtracted from the low-frequency dielectric constant to have an insight into the intrinsic dielectric behavior of SLBO glasses. The imaginary part of electric modulus spectra was modeled using an approximate solution of Kohlrausch–Williams–Watts relation. The dielectric constant for the as-quenched glass increased with increasing temperature and exhibited anomalies in the vicinity of the glass transition and crystallization temperatures.

Transparent $BaNaB_{9}O_{15} (BNBO)$ glasses were fabricated via the conventional melt-quenching technique. X-ray powder diffraction combined with differential scanning calorimetric studies carried out on as-quenched samples confirmed their amorphous and glassy nature, respectively. The dielectric constants in the 1 kHz–10MHz frequency range for BNBO glasses were determined as a function of the temperature (300–1023 K). The dielectric constant for the as-quenched glass increased with increasing temperature, exhibiting anomalies in the vicinity of the glass transition and crystallization temperatures. The frequency dependent characteristics of conductivity and dielectric constant were analysed using a derivative solution of Jonscher’s power law.

This paper has considered the selection of the optimal processing parameter (sintering temperature) leading to best possible properties of K0.5Na0.5NbO3 (KNN) for electromechanical applications. Vital piezoelectric properties for such applications include the piezoelectric coupling coefficient (kp), piezoelectric coefficient (d31), Curie temperature (Tc), remanent polarization (Pr), coercive field (Ec), density (ρ), elastic compliance ( S 11 E and S 12 E ) and dielectric loss (tan δ). The weights and priority of these physical properties for KNN are calculated using the modified digital logic (MDL) method. The priority order of these properties used for the selection of optimal processing parameters is as d 31 > tan δ > S 11 E = S 12 E > T c = P r > ρ > k p > E c . The weights obtained using MDL are further incorporated with analytic hierarchy process (AHP) and VlseKriterijumska Optimisacija I Kompromisno Resenje (VIKOR) in order to determine the optimal sintering temperature for KNN. Both methods suggest that 1080 °C and 1120 °C are the most and least desirable sintering temperatures, respectively. Finally, sensitivity analysis is performed for the robustness of our results and prediction of most influential parameter in terms of sensitivity. tan δ is found to be the most sensitive property for alteration in the present ranking.