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The reliability of piezoelectric transformers (PTs) is dependent upon the quality of fabrication technique as any heterogeneity, prestress, or misalignment can lead to spurious response. In this paper, unipoled multilayer PTs were investigated focusing on high-power composition and co-firing profile in order to provide low-temperature synthesized high-quality device measured in terms of efficiency and power density. The addition of 0.2 wt% CuO into Pb0.98Sr0.02(Mg1/3Nb2/3)0.06(Mn1/3Nb2/3)0.06(Zr0.48Ti0.52)0.88O3 (PMMnN-PZT) reduces the co-firing temperature from 1240 °C to 930 °C, which allows the use of Ag/Pd inner electrode instead of noble Pt inner electrode. Low-temperature synthesized material was found to exhibit excellent piezoelectric properties ( Qm = 1300 , kp= 0.47 , \tan \delta = 0.4 %, d_{33} = 218 pC/N, and T_{c}= 325$ °C). The performance of the PT co-fired with Ag/Pd electrode at 930 °C was similar to that co-fired at 1240 °C with Pt electrode (25% reduction in sintering temperature). Both high- and low-temperature synthesized PTs demonstrated 5-W output power with >90% efficiency and 11.5 W/cm3 power density. [ABSTRACT FROM AUTHOR]

A mathematical model for a thermoelectric generator (TEG) based on constitutive equations has been developed to analyze temperature dependent performance in terms of output power and efficiency. Temperature dependent material properties and thermal losses, which occur as conductive and radiative heat transfer, were considered in the finite element model. Effective material properties were invoked for understanding the influence of temperature dependence of material parameters and related adverse effects on the model TEG. It is shown that analytical equations with effective properties can provide excellent estimation of the performance of a TEG over a broad operating range. The model was simulated, analyzed and validated to examine the effects of different operating conditions and geometry that interact with thermal losses inside the TEG. We believe that this model will further expedite the optimization of TEGs being developed using new material compositions. [ABSTRACT FROM AUTHOR]

This paper is concerned with the development of a piezoelectric d15 shear-induced torsion actuator made of a lead-free piezoceramic material exhibiting giant piezoelectric shear stress coefficient (e15) and piezoelectric transverse shear actuation force comparable to that of lead-based shear-mode piezoceramics. The Mn-modified 0.93(Na0.5Bi0.5TiO3)-0.07BaTiO3 (NBT-BT-Mn) composition exhibited excellent properties as a torsional transducer with piezoelectric shear stress coefficient on the order of 11.6 C m-2. The torsional transducer, consisting of two oppositely polarized NBT-BT-Mn d15 mode piezoceramic shear patches, provided a rate of twist of 0.08 mm m-1 V-1 under quasi-static 150 V drive. The high value of piezoelectric shear d15 coefficient in NBT-BT-Mn sample further demonstrated its potential in practical applications. These results confirm that the lead-free piezoceramics can be as effective as their lead-based counterparts. [ABSTRACT FROM AUTHOR]

We demonstrate a microscale vibration energy harvester exhibiting an ultra-low resonance frequency and high power density. A spiral shaped microelectromechanical system (MEMS) energy harvester was designed to harvest ambient vibrations at a low frequency (<200 Hz) and acceleration (<0.25 g). High quality Pb(Zr0.48Ti0.52)O3 (PZT) film with 1.8 \mu \textm -thickness exhibiting remanent polarization of 36.2 \mu \textC /cm2 and longitudinal piezoelectric constant of 155 pm/V was synthesized to achieve high efficiency mechanical to electrical conversion. The experimental results demonstrate an ultra-low natural frequency of 48 Hz for MEMS harvester. This is one of the lowest resonance frequency reported for the piezoelectric MEMS energy harvester. Further, the position of the natural frequency was controlled by modulating the number of spiral turns and weight of the proof mass. The vibration mode shape and stress distribution were validated through a finite element analysis. The maximum output power of 23.3 nW was obtained from the five turns spiral MEMS energy harvester excited at 0.25 g acceleration and 68Hz. The normalized area and the volumetric energy density were measured to be 5.04\times 10^-4~ \mu \textW /mm ^2~\cdot ~\textg^2~\cdot Hz and 4.92\times 10^-2 ~ \mu \textW /mm ^3~\cdot ~\textg^2~\cdot Hz, respectively. [2017-0018] [ABSTRACT FROM PUBLISHER]

While piezoelectric- ferroelectric materials offer great potential for nonvolatile random access memory, most commonly implemented ferroelectrics contain lead which imposes a challenge in meeting environmental regulations. One promising candidate for lead-free, ferroelectric material based memory is ( 1 − x ) B a T i O 3 − x B a ( C u 1 / 3 N b 2 / 3 ) O 3 (BT-BCN), x = 0.025 . The samples studied here were grown on a Si substrate with an HfO 2 buffer layer, thereby preventing the interdiffusion of BT-BTCN into Si. This study provides further insight into the physical behavior of BT-BCN that will strengthen the foundation for developing switching devices. The sample thicknesses ranged from 1.5 to 120 nm, and piezoelectric force microscopy was employed in order to understand the local ferroelectric behaviors. Dielectric constant as a function of frequency demonstrated enhanced frequency dispersion indicating the polar nature of the composition. The relative permittivity was found to change significantly with varying bias voltage and exhibited a tunability of 82%. The difference in the peak position during up and down sweeps is due to the presence of the spontaneous polarization. Furthermore, reflectometry was performed to determine the refractive index of samples with differing thicknesses. Our results demonstrate that refractive indices are similar to that of barium titanate. This is a promising result indicating that improved ferroelectric properties are obtained without compromising the optical properties. [ABSTRACT FROM AUTHOR]

In this work, a comparison between the performance of two- and three-stage cascaded thermoelectric generator (TEG) devices is analyzed based on a prescribed maximum hot side temperature of 973 K, an imposed maximum heat input of 505 W, and a fixed cold side temperature of 473 K. Half-Heusler is used as a thermoelectric (TE) material in the top higher temperature stage and skutterudite as a TE in the bottom lower temperature stage for the two-stage structure. Lead telluride is added in the middle stage to form the three-stage structure. Based on the prescribed constraints, the two-stage cascaded TEG is found to produce a power output of 42 W with an efficiency of 8.3%. The three-stage cascaded TEG produces a power output of 51 W with an efficiency of 10.2%. The three-stage cascaded TEG produces 21% more power than the two-stage does; however, if the system complexity, mechanical robustness, manufacturability, and/or cost of three-stage cascaded TEG outweigh the 21% percent power production increase, the two-stage TEG could be preferable. [ABSTRACT FROM AUTHOR]

Mechanical energy harvesters are needed for diverse applications, including self-powered wireless sensors, structural and human health monitoring systems, and the extraction of energy from ocean waves. We report carbon nanotube yarn harvesters that electrochemically convert tensile or torsional mechanical energy into electrical energy without requiring an external bias voltage. Stretching coiled yarns generated 250 watts per kilogram of peak electrical power when cycled up to 30 hertz, as well as up to 41.2 joules per kilogram of electrical energy per mechanical cycle, when normalized to harvester yarn weight. These energy harvesters were used in the ocean to harvest wave energy, combined with thermally driven artificial muscles to convert temperature fluctuations to electrical energy, sewn into textiles for use as self-powered respiration sensors, and used to power a light-emitting diode and to charge a storage capacitor. [ABSTRACT FROM AUTHOR]

1D ferroelectric nanostructures are promising for enhanced ferroelectric and piezoelectric performance on the nanoscale, however, their synthesis at the wafer scale using industrially compatible processes is challenging. In order to advance the nanostructure-based electronics, it is imperative to develop a silicon-compatible growth technique yielding high volumetric density and an ordered arrangement. Here, a major breakthrough is provided in addressing this need and ordered and close-packed single crystalline ferroelectric nanorod arrays, of composition PbZr0.52Ti0.48O3 (PZT), grown on commercial grade 3 in. silicon wafer are demonstrated. PZT nanorods exhibit enhanced piezoelectric and ferroelectric performance compared to thin films of similar dimensions. Sandwich structured architecture utilizing 1D PZT nanorod arrays and 2D reduced graphene oxide thin film electrodes is fabricated to provide electrical connection. Combined, these results offer a clear pathway toward integration of ferroelectric nanodevices with commercial silicon electronics. [ABSTRACT FROM AUTHOR]

This letter presents a voltage-controlled capacitor that varies from 20% to 100% of the rated capacitance (1 μF) with a control voltage from half of the voltage rating to 0 V. Capacitance, self-resonant frequency, and equivalent series resistance were measured with respect to the control voltage. An equivalent circuit and a nonlinear model derived from relationship between permittivity and electric field were created and implemented in SPICE. A buck converter with input of 12 V, output of 5 V, and switching frequency of 500 kHz was built to demonstrate the change from 85% to 40% of the rated capacitance of the voltage-controlled capacitor. The error between the simulation and experiment was limited within 10%, which verifies the model. [ABSTRACT FROM AUTHOR]

Information about a special workshop/symposium held at the Amari Orchid Hotel, Pattaya, Thailand on December 9-10, 2012 is presented. Topics discussed at the event include the basics of ferroics and multiferroics, the concepts of biomultiferroics and the scientific networking in international research groups. Future conferences about the science behind our sensory systems are also tackled.

This paper is concerned with the development of a piezoelectricd15shear-induced torsion actuator made of a lead-free piezoceramic material exhibiting giant piezoelectric shear stress coefficient (e15) and piezoelectric transverse shear actuation force comparable to that of lead-based shear-mode piezoceramics. The Mn-modified 0.93(Na0.5Bi0.5TiO3)-0.07BaTiO3(NBT-BT-Mn) composition exhibited excellent properties as a torsional transducer with piezoelectric shear stress coefficient on the order of 11.6 C m–2. The torsional transducer, consisting of two oppositely polarized NBT-BT-Mnd15mode piezoceramic shear patches, provided a rate of twist of 0.08 mm m–1 V–1under quasi-static 150 V drive. The high value of piezoelectric sheard15coefficient in NBT-BT-Mn sample further demonstrated its potential in practical applications. These results confirm that the lead-free piezoceramics can be as effective as their lead-based counterparts. [ABSTRACT FROM AUTHOR]

Dye sensitized solar cell (DSSC) has attracted tremendous attention over last two decades and is currently regarded as a promising alternative to the conventional flexible photovoltaic (PV) market. Thin, light-weight and flexible DSSC module enables deployment on curved surfaces which significantly widens the application space. The critical challenge in advancing flexible DSSC technology remains in the up-scaling of module dimensions. Herein, we report advancement achieved in developing large-scale flexible DSSC modules of the dimensions 100 mm×100 mm with conversion efficiency of 3.27%. A facile binder-free TiO 2 paste was synthesized to fabricate firm TiO 2 photoanode on plastic substrate at low temperature. Cold isostatic press (CIP) technique was utilized to not only improve the quality of film but also to increase the thickness of TiO 2 film. Based on binder-free TiO 2 paste, flexible DSSC module with dimension of 100 mm×100 mm was fabricated and demonstrated for mobile phone charging application under indoor light condition. [ABSTRACT FROM AUTHOR]

This study demonstrates the modulation of off-resonance magnetoelectric ( ME) response of the Pb(Zr,Ti)O3 ( PZT)/ Metglas (Fe BSi) bilayered composite by laser annealing. A continuous-wave 532 nm Nd: YAG laser with varying fluences (210-390 J/mm2) was utilized to anneal the 2 μm thick PZT film deposited using granule spray in vacuum ( GSV) technique on magnetostrictive amorphous Metglas foil. It was found that the dielectric and ferroelectric properties of the PZT film are strongly affected by the exposure to laser fluence. The ME voltage coefficient of PZT/Metglas increased with the fluence up to 345 J/mm2, reaching a high value of 880 mV/cm·Oe. The electrical and ME properties were correlated with the changes observed in crystallinity and grain size of the PZT film as well as with the alterations in microstructure and magnetic behavior of Metglas. Our results demonstrate that enhanced ME coupling can be realized in PZT/Metglas film composites by controlling the laser fluence. [ABSTRACT FROM AUTHOR]

Piezoelectric ceramics with combinatory soft and hard characteristics are highly desired for high-power applications. However, it remains grand challenge to achieve simultaneous presence of hard (e.g. high coercive field, E c ; high mechanical quality factor, Q m) and soft (e.g. high piezoelectric constant, d ; high electromechanical coupling factor, k) piezoelectric properties in piezoelectric ceramics since the mechanism controlling the hard behavior (pinned domain walls) will significantly reduce the soft behavior. Here, we address this grand challenge and demonstrate <001> textured MnO 2 and CuO co-doped Pb(In 1/2 Nb 1/2)O 3 - Pb(Mg 1/3 Nb 2/3)O 3 -PbTiO 3 (PIN-PMN-PT) ceramics exhibiting ultrahigh combined soft and hard piezoelectric properties (d 33 = 713 pC N−1, k 31 = 0.52, Q m ≈950, E c = 9.6 kV cm−1, tan δ = 0.45%). The outstanding electromechanical properties are explained by considering composition/phase selection, crystallographic anisotropy and defect engineering. Phase-field model in conjunction with high resolution electron microscopy and diffraction techniques is utilized to delineate the contributions arising from intrinsic piezoelectric response, domain dynamics, and local structural heterogeneity. These results will have significant impact in the development of high-power transducers and actuators. [Display omitted] [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including measuring and modeling of ferroic materials as well as multiferroics, role of interfaces, domains and microstructure and microwave interaction with the brain tissue.

Mode shapes in the design of mechanical energy harvesters, as a means of performance increase, have been largely overlooked. Currently, the vast majority of energy harvester designs employ some variation of a single-degree-of-freedom cantilever, and the mode shapes of such beams are well known. This is especially true for the first bending mode, which is almost exclusively the chosen vibration mode for energy harvesting. Two-dimensional beam shapes (those which curve, meander, spiral, etc., in a plane) have recently gained research interest, as they offer freedom to modify the vibration characteristics of the harvester beam for achieving higher power density. In this study, the second bending mode shape of the "Elephant" two-dimensional beam shape is examined, and its interaction with the first bending mode is evaluated. A combinatory mode shape created by using mass loading structural modification to lower the second bending modal frequency was found to interact with the first bending mode. This is possible since the first two bending modes do not share common areas of displacement. The combined mode shape is shown to produce the most power of any of the considered mode shapes. [ABSTRACT FROM AUTHOR]

This paper describes the fabrication and performance results of a magnetoelectric macro fiber composite (ME MFC). The magnetoelectric composite was fabricated by bonding a magnetostrictive layer to a piezoelectric layer using a novel approach of low temperature transient liquid phase (LTTLP) bonding. The composite was diced into 150 micron wide fibers and bonded to a custom designed copper flexible circuit using a spin coated low viscosity room temperature curing epoxy. ME MFC’s with varying ferrite thicknesses of 0.6 mm and 0.5 mm were fabricated and characterized for energy harvesting. The composite with 0.6 mm ferrite thickness achieved an open circuit voltage of 101 mV (ME voltage coefficient of 6740 mV/cmOe) and peak power of 3.1 nW across 356 kΩ matching load at 264 Hz. [ABSTRACT FROM AUTHOR]

The (1− x)BiFeO3- xBaTiO3 (with x = 0.1, 0.2, 0.3, and 0.4) ceramics were fabricated successfully by solid-state reaction method. Single-phase perovskite was obtained in all ceramics, as confirmed by XRD technique. It was observed that 0.7BiFeO3-0.3BaTiO3 was the morphotropic phase boundary ( MPB) between rhombohedral and cubic phases, as also revealed from ferroelectric and magnetic properties. The simulated and experimental X-Ray Absorption Spectroscopy ( XAS) study revealed that BT in 0.75BF-0.25BT is possibly taken a rhombohedral structure. Furthermore, the rounded ferroelectric hysteresis loops observed for 0.9BiFeO3-0.1BaTiO3 and 0.8BiFeO3-0.2BaTiO3 compositions could be attributed to their microstructure and surface charge effects and electron transfer between Fe3+ and Fe2+ ions. It was also found that high dielectric constant of 0.9BiFeO3-0.1BaTiO3 composition was a result of grain and grain-boundary effects, as observed in SEM micrographs. In addition, a strong signature of dielectric relaxation behavior was observed in this ceramic system with the activation energy 0.467 eV obtained from the Arrhenius' law. Finally, the local structure investigation with XAS technique provided additional information to better understand the electric and magnetic properties in the BF- BT ceramic system. [ABSTRACT FROM AUTHOR]

• Decoupled backpack generates energy from the pack-mass suspended only on springs. • Power and efficiency derivation for semi-coupled, decoupled and coupled backpacks. • Coupled and semi-coupled harvester response is verified using Simulink models. • Experimental coupled backpack harvesters indicated high normalized force. • Efficiency of semi-coupled and decoupled backpacks is higher than coupled backpack. Harvesting energy from human motion has the potential to power wearable sensors and low power portable systems. Here, a backpack harvester that generates electrical energy by suspending the pack-mass only on springs is demonstrated. In this mechanism, the relative motion between a fixed frame (relative to the body) and a suspended frame winds a torsional spring that serves as a mechanical reservoir in one-half of the oscillation cycle (one walking step). In the second half cycle, the stored energy is released to the generator. This approach eliminates the damping force from the generator on the human bearing the load. As the load is suspended on springs and does not directly drive the generator, the proposed system results in a decoupled harvester. Experimental results demonstrate that the output power generated from the decoupled harvester is 65% of that obtained from a semi-coupled harvester with 52% smaller backpack displacements and oscillatory forces. The decoupled and semi-coupled backpack harvesters achieved 53% and 45% efficiency at 1.4 m/s walking speed compared to 34% efficiency in a fully coupled harvester. This demonstrates significant advancement towards developing decoupled backpack energy harvesters that suspend pack-mass only on springs. [ABSTRACT FROM AUTHOR]

A highly dense, 4 lm-thick Pb(Zr,Ti)O3 (PZT) film is deposited on amorphous magnetostrictive Metglas foil (FeBSi) by granule spray in vacuum process at room temperature, followed by its localized annealing with a continuous-wave 560 nm ytterbium fiber laser radiation. This longerwavelength laser radiation is able to anneal the whole of thick PZT film layer without any deteriorative effects, such as chemical reaction and/or atomic diffusion, at the interface and crystallization of amorphous Metglas substrate. Greatly enhanced dielectric and ferroelectric properties of the annealed PZT are attributed to its better crystallinity and grain growth induced by laser irradiation. As a result, a colossal off-resonance magnetoelectric (ME) voltage coefficient that is two orders of magnitude larger than previously reported output from PZT/Metglas film-composites is achieved. The present work addresses the problems involved in the fabrication of PZT/Metglas filmcomposites and opens up emerging possibilities in employing piezoelectric materials with low thermal budget substrates (suitable for integrated electronics) and designing laminate composites for ME based devices. [ABSTRACT FROM AUTHOR]

In this paper, we discuss how the material parameters of piezoelectric phase affect the magnetoelectric properties of the laminate composite especially focusing on the role of loss factors and electromechanical resonance of piezoelectric phase. By analyzing experimental results of magnetoelectric laminate composite consisting of Pb(Zr,Ti)O3-based piezoelectric layer and Metglas ferromagnetic layers, we demonstrate that the losses of piezoelectric materials play an important role in controlling the magnetoelectric sensitivity of the laminate composite. Further, we show that direct magnetoelectric effect is maximized at anti-resonance frequency while the converse magnetoelectric effect is maximized at resonance frequency of the laminate composite. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the laser Doppler vibrometry based measurement of the magnetostriction in magnetic thin films. Using this method, the strain induced by an AC magnetic field in the polycrystalline cobalt ferrite and nickel ferrite thin films grown on silicon and platinized silicon substrates was measured under a DC magnetic bias. The experimental setup and the derivation of the magnetostriction constant from the experimentally measured deflection values are discussed. The magnetostriction values derived using force and bending moment balances were compared with that derived from an industry standard relationship. In addition, we corroborate our approach by comparing the values derived from bending theory calculations of magnetically induced torque to those from measurements using Vibrating Sample Magnetometer (VSM). At high DC magnetic field bias, the magnitude of magnetization calculated from the measured magnetostriction was found to match the measured magnetization by VSM. [Copyright &y& Elsevier]

We report a simple, eco-friendly facile wet chemical nitrate precursor route for the synthesis of pristine and nickel-containing nanocrystalline (∼44 nm) α-Fe2O3. Thermal analysis of the dried (∼70 °C) presumed oxalate powder, Fe2(C2O4)3 · 4H2O (also confirmed by X-ray diffraction), revealed two-step formation of the oxide; slower reaction as Fe2(C2O4)3 · 4H2O↓ → 4H2O↑ + 2CO2↑ + 2FeC2O4↓ and faster as 2FeC2O4 → Fe2O3↓ + CO2↑ + 3CO↑. The incorporation of nickel resulted in progressive increase of cell parameters and exhibited decrease in estimated direct and indirect band gap values. The direct band gap values were in close correlation with emission transitions. The direct nature and narrowing of band gap with nickel addition ensures the higher absorbance values and wider spectrum of absorbance; indicating the enhanced semiconducting properties for applications such as solar cells, photocatalytic activity, etc. Regarding magnetic properties, the saturation magnetization increased progressively with nickel content while coercivity reduced up to 2 wt% of Ni content and increased afterward. The resistivity values with nickel incorporation decreased, when substituted at Fe3+ sites. [ABSTRACT FROM AUTHOR]

• Large, thin, and light-weight thermoacoustic projectors benefit from encapsulation • Plate-cavity coupling modifies vibration modes of the plate • Modified vibration profile is favorable for plane-wave radiation of the sound • Proper choice of cavity and plate geometry provides a desirable performance • Increase of acoustic stiffness of the entrained gas increases the bandwidth of device • Coupling of internal pressure with modified modes provides a high performance The problem of coupled panel-cavity vibrations is addressed by studying the resonance modes in high power, low frequency, encapsulated thermoacoustic sound projectors using scanning laser vibrometry and sound pressure measurements. We fabricated and analyzed the performance of large area thermoacoustic sound projectors based on freestanding carbon nanotube sheets, encapsulated between a heat sink and various rigid vibrating plates. For thin, simply-supported vibrating plates we observed a strong deviation of resonance frequency and sound intensity from theoretical prediction for in vacuo plates. The domination of symmetric, odd modes for thin plates, with substantially improved sound radiation, is attributed to the coupled panel-cavity modes produced by harmonically varying pressure within the cavity. The observed modified mode shapes result from a minimum energy principle, wherein the potential energy stored in the entrained gas is minimized by reducing the overall change of the cavity gas volume. The effect of plate and cavity thickness on thermoacoustic projector performance in air is described for various devices. The optimized ultralight, low volume sound projectors can generate a remarkably high sound pressure level in air of over 120 dB re 20 μPa @ 1 m in a frequency range of 500 - 3000 Hz. [Display omitted] [ABSTRACT FROM AUTHOR]

We demonstrate a 33-mode piezoelectric structure with zigzag shape for high sensitivity magnetoelectric laminates. In contrast to the 33-mode macro fiber composite (MFC), this zigzag shape piezoelectric layer excludes epoxy bonding layer between the electrode and piezoelectric materials, thereby, significantly improving the polarization degree, electromechanical coupling, and the stability of loss characteristics. The polarization degree was monitored from the change in phase angle near resonance, and the loss stability was determined from the changes in dielectric loss and rate of capacitance variation defined by (C - Cf)/Cf, where C is capacitance at a given frequency and Cf is capacitance at 100 Hz. Magnetoelectric composite with zigzag patterned piezoelectric layer was found to exhibit giant magnetoelectric response both in low frequency off-resonance region (6.75Vcm-1 Oe-1 at 1 kHz) and at anti-resonance frequency (357Vcm-1 Oe-1). [ABSTRACT FROM AUTHOR]

〈001〉pc textured K0.5Na0.5NbO3 (KNN) ceramic was found to exhibit a 65% improvement in the longitudinal piezoelectric response as compared to its random counterpart. Piezoresponse force microscopy study revealed the existence of larger 180° and non-180° domains for textured ceramic as compared to the random ceramic. Improvement in piezoresponse by the development of 〈001〉pc texture is discussed in terms of the crystallographic nature of KNN and domain morphology. A comparative analysis performed with a rhombohedral composition suggested that the improvement in longitudinal piezoresponse of polycrystalline ceramics by the development of 〈001〉pc texture is determined by the crystal structure. [ABSTRACT FROM AUTHOR]

Abstract: This paper provides the correlation between the compositions of a given thin film to its optical dispersion properties. Gladstone–Dale (G–D) relationships have been used in optical mineralogy to relate density of crystalline compounds to their average refractive index. We purport to use a ‘reverse’ G–D approach and determine the composition of multi-component thin films from their optical properties. As a model system, we focus on complex perovskite ferroelectric thin film and apply the derived relationships to determine the stoichiometry. The wavelength dispersion of refractive index and extinction coefficient of various Pb(Zr,Ti)O3 (PZT) thin films was measured using Variable Angle Spectroscopic Ellipsometry. Elemental compositions were measured using Energy Dispersive X-ray analysis and Electron Probe Micro Analysis. Wemple–DiDomenico, Jackson–Amer, Tauc and Urbach optical relationships and related parameters were used to extract correlations to elemental content. Both theoretical and semi-empirical approaches to calculate the electronic polarizability of PZT were employed and their variation with elemental content was computed. Perovskite tolerance and octahedral factors were also analyzed against the optical and polarizability parameters. Lastly, these factors and relationships were combined to realize a model for predicting the elemental content of a thin film system. [Copyright &y& Elsevier]

In this preliminary study, we report the mechanical and dielectric properties of polyvinyl alcohol (PVA)-ferritin hydrogel. This material was found to exhibit close resemblance toAurelia aurita(jellyfish) mesoglea in terms of stiffness modulus and water content. Systematic experiments were conducted on natural jellyfish to identify its compression modulus a function of deformation. In compressive testingAurelia auritamesoglea was found to exhibit nonlinear modulus in the range of −10 kPa to 70 kPa depending upon the compressive strain (0–50% strain). The negative stiffness is an artifact of tensile force experienced by the specimen at the beginning of the test due to surface tension. PVA hydrogels with 60% water to dimethyl sulfoxide (DMSO) ratio without ferritin particle (H60) and PVA hydrogels with 80% water to DMSO ratio with ferritin particle (F80) provided a good alternative to natural jellyfish mesoglea exhibiting shear modulus of 33.06 Pa and 39.99 Pa respectively as compared to 4.75 Pa forAurelia auritamesoglea. This is a significantly better match compared to the 1041.67 Pa shear modulus of Ecoflex, a soft polymer material commonly used in biomimetic robotics. A Mooney Rivlin model suggests that H60 and F80 compositions are about 6.9 times and 8.4 times stiffer than naturalAurelia aurtiamesoglea whereas Ecoflex is 219 times as stiff. Nanocomposite hydrogel consisting of PVA matrix and ferritin nanoparticles were found to exhibit higher durability over regular PVA hydrogels and had more consistent properties due to increased cross-linking at ferritin nanoparticle sites. The ferritin nanoparticles were found to act as springs, increasing the modulus by increasing the surface area of the cross-linked polymer chains and disrupting long linear chain patterns of the polymer. NaturalAurelia auritawas found to have water content of 96.3% with a standard deviation of 0.57% as compared to 85% water content of PVA-ferritin hydrogels. Use of this material in the design of biomimetic unmanned underwater vehicles is expected to reduce the power consumption, increase swimming efficiency, and better replicate the rowing kinematics of naturally occurringAurelia aurita. [ABSTRACT FROM AUTHOR]

Gelatinous zooplankton populations are well known for their ability to take over perturbed ecosystems. The ability of these animals to outcompete and functionally replace fish that exhibit an effective visual predatory mode is counterintuitive because jellyfish are described as inefficient swimmers that must rely on direct contact with prey to feed. We show that jellyfish exhibit a unique mechanism of passive energy recapture, which is exploited to allow them to travel 30% further each swimming cycle, thereby reducing metabolic energy demand by swimming muscles. By accounting for large interspecific differences in net metabolic rates, we demonstrate, contrary to prevailing views, that the jellyfish (Aurelia aurita) is one of the most energetically efficient propulsors on the planet, exhibiting a cost of transport (joules per kilogram per meter) lower than other metazoans. We estimate that reduced metabolic demand by passive energy recapture improves the cost of transport by 48%, allowing jellyfish to achieve the large sizes required for sufficient prey encounters. Pressure calculations, using both computational fluid dynamics and a newly developed method from empirical velocity field measurements, demonstrate that this extra thrust results from positive pressure created by a vortex ring underneath the bell during the refilling phase of swimming. These results demonstrate a physical basis for the ecological success of medusan swimmers despite their simple body plan. Results from this study also have implications for bioinspired design, where low-energy propulsion is required. [ABSTRACT FROM AUTHOR]

In this study, we report an optical crystallographic study of KxNa1−xNbO3 (x = 0.4, 0.5 and 0.6) single crystals in the temperature range of 30–600 °C. At room temperature, these three compositions were found to exhibit monoclinic MC, monoclinic MA/MB and orthorhombic symmetries respectively. All the compositions showed a transformation to tetragonal and to cubic symmetries around 200 °C and 400 °C respectively. In the tetragonal phase field (200–400 °C), coexistence of a lower symmetry phase was also evident. In the paraelectric regime (400–600 °C), all crystals exhibited non-zero birefringence, suggestive of deviation from ideal cubic symmetry m3̅m. Furthermore, crystals of the morphotropic phase boundary composition (x = 0.5) were found to have very small and organized domains, as compared to the other two compositions. [ABSTRACT FROM AUTHOR]

Grain orientation, BaTiO3 heterogeneous template content, and electrode materials are expected to play an important role in controlling the polarization fatigue behavior of <001> textured Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics. A comparative analysis with randomly oriented ceramics showed that <001> grain orientation/texture exhibits improved fatigue characteristics due to the reduced switching activation energy and high domain mobility. The hypothesis was validated from the systematic characterization of polarization-electric field behavior and domain wall density. The defect accumulation at the grain boundary and clamping effect arising from the presence of BaTiO3 heterogeneous template in the final microstructure was found to be the main cause for polarization degradation in textured ceramic. [ABSTRACT FROM AUTHOR]

The influence of alternating (ac) and direct current (dc) fields on the structural and dielectric properties of [001]PC textured Na0.5Bi0.5TiO3-7%BaTiO3 (NBT-7%BT) ceramics has been investigated. X-ray diffraction measurements revealed that the depolarization at temperature Td in poled samples resulted from a tetragonal → pseudo-cubic transition on heating. Moderate ac drive and dc bias had opposite influences on Td: ac drive decreased the Td, whereas dc bias increased it. These investigations suggested an effective method to expand the working temperature range of NBT-x%BT textured ceramics to a high temperature. [ABSTRACT FROM AUTHOR]

The novel Cu- and Mn-doped and Cu/Mn codoped 0.75BiFeO-0.25BaTiO magnetoelectric ceramics were successfully prepared by a solid-state reaction method. The dielectric, ferroelectric, ferromagnetic, and magnetoelectric properties were determined and all the results suggested that Cu and Mn dopants occupied different B-site lattices in the 0.75BiFeO-0.25BaTiO structure. To identify the preferential sites of Cu and Mn in the lattice, Synchrotron X-ray Absorption Spectroscopy (SXAS) measurements were carried out. A combination of both measured and simulated XAS results with a linear combination fitting (LCF) revealed that in Cu- and Mn-doped 0.75BiFeO-0.25BaTiO ceramics both Mn and Cu substituted at Fe-site and Ti-site with slightly different proportion. On the other hand, both dopants were found to occupied different sites in Cu/Mn codoped 0.75BiFeO-0.25BaTiO ceramics. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate self-biased magnetoelectric effect in homogenous two-phase magnetostrictive-piezoelectric laminates. Our results illustrate the method for tuning the magnitude of self-bias effect and provide understanding behind the hysteretic changes. We model this phenomenon by considering the magnetization hysteresis with shape-induced demagnetization effect. The self-biased response was found to be directly related to the nature of magnetization and can be tuned by variation in demagnetization state and the resultant differential magnetic flux distribution. These results present significant advancement toward development of AC magnetic field sensor and magnetoelectric composite based on-chip devices by eliminating the need for DC bias. [ABSTRACT FROM AUTHOR]

Flexible bell margins are characteristic components of rowing medusan morphologies and are expected to contribute towards their high propulsive efficiency. However, the mechanistic basis of thrust augmentation by flexible propulsors remained unresolved, so the impact of bell margin flexibility on medusan swimming has also remained unresolved. We used biomimetic robotic jellyfish vehicles to elucidate that propulsive thrust enhancement by flexible medusan bell margins relies upon fluid dynamic interactions between entrained flows at the inflexion point of the exumbrella and flows expelled from under the bell. Coalescence of flows from these two regions resulted in enhanced fluid circulation and, therefore, thrust augmentation for flexible margins of both medusan vehicles and living medusae. Using particle image velocimetry (PIV) data we estimated pressure fields to demonstrate a mechanistic basis of enhanced flows associated with the flexible bell margin. Performance of vehicles with flexible margins was further enhanced by vortex interactions that occur during bell expansion. Hydrodynamic and performance similarities between robotic vehicles and live animals demonstrated that the propulsive advantages of flexible margins found in nature can be emulated by human-engineered propulsors. Although medusae are simple animal models for description of this process, these results may contribute towards understanding the performance of flexible margins among other animal lineages. [ABSTRACT FROM AUTHOR]

Abstract: The high vibration levels inside a tire have the potential to generate electrical power using vibration based energy harvesting techniques. In this paper, the feasibility of using an inertial vibrating energy harvester unit to power a sensor module inside the tire is assessed. The harvester unit is adapted to the tire vibration spectra and the superimposed acceleration signal. First prototypes demonstrate power generation capabilities sufficient enough to transmit tire sensor data multiple times per minute. To optimize the harvester performance with changing dominant tire vibration frequencies, a novel artificial neural network (ANN) based closed loop system capable of ensuring broad band operations has been proposed. By presenting a batteryless power supply unit, the proposed system addresses one of the key challenges in the realization of the intelligent tire concept. [Copyright &y& Elsevier]

Abstract: High energy density piezoelectric ceramics, 0.8[Pb(Zr0.52Ti0.48)O3]–0.2[Pb(Zn1/3Nb2/3)O3 +2mol%MnO2 (PZZNT), were synthesized and their mechanical behavior was investigated by conducting tensile, bending and fracture toughness tests. Direct tensile testing of ceramics was achieved by optimizing the sample dimensions and by identifying the proper gripping method. Through these investigations, elastic modulus was calculated in the linear region of the stress–strain curves from both bending and tensile tests. The average magnitude of modulus was found to be 54±7GPa and 66±4GPa for tensile and bending test respectively. Fracture toughness was measured to be in the range of 1.07–1.20MPa√m. [Copyright &y& Elsevier]

This letter provides a comparative description of the properties of textured and randomly oriented poly-crystalline lead-free piezoelectric 0.93(Na0.5Bi0.5TiO3)-0.07BaTiO3 (NBT-BT) ceramics. A high longitudinal piezoelectric constant of (d33) ∼ 322 pC/N was obtained in (001)PC textured NBT-7BT ceramics, which is almost ∼2× times the d33 coefficient reported for randomly oriented ceramics of the same composition. In situ neutron diffraction experiments revealed that characteristically different structural responses are induced in textured and randomly oriented NBT-BT ceramics upon application of electric fields (E), which are likely related to the varying coherence lengths of polar nanoregions and internal stresses induced by domain switching. [ABSTRACT FROM AUTHOR]

This study reports the magnetoelectric (ME) response of lead-free particulate composites given as (1− x)[0.948 K0.5Na0.5NbO3-0.052 LiSbO3]- xNi0.8Zn0.2Fe2O4 (KNNLS-NZF) and bimorph laminates given as KNNLS-NZF/Ni/KNNLS-NZF. The particulate ME composites were found to exhibit island-matrix microstructure as confirmed by scanning electron microscopy and elemental mapping. Detailed investigations were conducted on optimization of the magnitude of magnetic and piezoelectric properties by varying the sintering condition and NZF mole fraction. It was found that longitudinal piezoelectric strain coefficient d33 and electromechanical coupling factor kp decreased with increasing NZF concentration. On the other hand, the magnitude of saturation magnetization Ms, remnant magnetization Mr, magnetic permeability μ, and magnetostriction λ was found to increase with increasing NZF fraction. The composition 0.7 KNNLS-0.3 NZF sintered at 1060°C was found to exhibit d33 of 73 pC/N, Ms of 19 emu/g, and maximum ME coefficient αE of 20.14 mV/cm·Oe under Hac=1 Oe at 1 kHz. The bimorph laminates were fabricated by embedding Ni plate between (1− x)KNNLS- xNZF disks with varying electrical connections to achieve radial and bending modes. The radial mode laminates were found to exhibit typical ME response without any self-bias effect with maximum αE of 261.3 mV/cm·Oe and high DC magnetic field sensitivity of 1 μT at 1 kHz. The bending mode laminates were found to exhibit self-biased ME response whose magnitude and shape was dependent upon the NZF concentration. [ABSTRACT FROM AUTHOR]

Piezoelectric sensors have been previously used for continuous structural health monitoring using impedance spectroscopy. However, three important issues still remain to be investigated for efficient design of such sensors, namely (i) the effect of sensor geometry on sensitivity of impedance based damage detection, (ii) the selection of frequency band for continuous health monitoring, and (iii) identification of damage quantification metric. In this study, we address these issues and report the results on aluminum beam subjected to mechanical fatigue. A commercially available Materials Testing Machine was used in order to perform a load controlled fatigue test (250–1350 lbs @ 20 cycles/sec) on a notched aluminum beam. Sensor geometry was optimized with the help of damage index metric based health monitoring. Next, optimized geometry was selected to further study the selection of frequency band with a new approach based on number of peaks in the impedance signature under identical testing conditions. The results of this study provide a benchmark for designing the sensors for structural health monitoring. [ABSTRACT FROM AUTHOR]

Advancement in internet, automation and data communication has led to massive growth in global knowledge-base over the past few decades. It has opened the possibility of developing global research laboratories where experiments and measurement systems can be shared in real time. The global magnetoelectric measurement system (GMMS) developed in this paper allows remote measurement of magnetoelectric properties of single phase and composite samples with ultra-high sensitivity, reducing the operation time from 2–3 hours to approximately 15 minutes. A secure website was developed to (i) create the internet-based control of the measurement system, (ii) compile, email and download the experimental results and (iii) video conferencing between the users. The magnetoelectric measurement system includes an electromagnetic coil to generate DC magnetic field up to 1.5 T, a Helmholtz coil, function generator, high power supply, and a translational stage with a 2 DOF gripper which allows measurements from L-T to T-T mode. [ABSTRACT FROM AUTHOR]

Abstract: We report the effect of top electrode diameter size in aerosol deposited Pb(Zr0.52Ti0.48)O3 thick films (~10μm-thick) with Pt top and bottom electrode. Dielectric and ferroelectric results showed that top electrode diameter of 0.5–1mm provides reasonable performance with 1mm being the most suitable dimension in wide range of AC electric field and frequency. The results were discussed based on the surface microstructure and Debye relaxation. The dielectric analysis showed that the properties variation was mainly due to average grain size and defect density. Debye relaxation modeling exhibited that the result is because of materials characteristic not measurement artifact. We believe the results of this study will find immediate application in design of aerosol deposition process. [Copyright &y& Elsevier]

Magnetoelectric (ME) composites that simultaneously exhibit ferroelectricity and ferromagnetism have recently gained significant attention as evident by the increasing number of publications. These research activities are direct results of the fact that multiferroic magnetoelectrics offer significant technological promise for multiple devices. Appropriate choice of phases with co-firing capability, magnetostriction and piezoelectric coefficient, such as Ni-PZT and NZFO-PZT, has resulted in fabrication of prototype components that promise transition. In this manuscript, we report the properties of Ni-PZT and NZFO-PZT composites in terms of ME voltage coefficients as a function of frequency and magnetic DC bias. In order to overcome the problem of toxicity of lead, we have conducted experiments with Pb-free piezoelectric compositions. Results are presented on the magnetoelectric performance of Ni-NKN, Ni-NBTBT and NZFO-NKN, NZFO-NBTBT systems illustrating their importance as an environmentally friendly alternative. [ABSTRACT FROM AUTHOR]

Multimodal energy harvester comprising of magnetostrictive and electromagnetic system was designed and analyzed with overall shape and size similar to AA battery. In the proposed design, magnetostrictive plates were mounted on the base and top cap of the harvester. The cylindrical shell housed a magnetic levitation cavity where center magnet was suspended between the top and bottom magnet attached to the base and top cover. This design allows the system to harvest energy from magnetostrictive material through Villari effect and from the oscillating permanent magnet within a hollow cavity through Faraday's effect. By specifying generator geometry and estimating system parameters, theoretical output power for the proposed design was determined for two different center magnet geometry. The output power and voltage was analyzed using the analytical and FEM modeling to identify the overall response of the multimodal structure. [ABSTRACT FROM AUTHOR]

We report the success in synthesis of BaTiO3 (BTO) coating on acid-treated functionalized multiwall carbon nanotubes (MWCNTs). Functionalization treatment, coating temperature, and coating time were optimized in order to obtain the dense coating of BTO. Contact angle measurements were conducted on MWCNT surface to quantify the effectiveness of functionalization and were correlated with percentage coating. Coating thickness in the range of 5-15 nm was confirmed by using high-resolution transmission electron microscopy. X-ray photoelectron spectroscopy was used to confirm the formation of BTO perovskite phase. Microstructural characterization and elemental analysis were performed using scanning electron microscopy and energy-dispersive spectroscopy to confirm the homogeneous coating with high yield. Possible application of these fully coated MWCNTs can be in flexible pressure sensors. [ABSTRACT FROM AUTHOR]

The article discusses the impact of elemental diffusion on temperature coefficient piezoelectric aspects in KNN-base lead-free composite materials. Compared to lead-free compositions, based ceramics are considered as one of the potential candidate because of their piezoelectric properties and high Curie temperature. Schematic diagrams of microstructure formation in a island-matrix and b layered structure are presented.

We report the synthesis and characterization of BaTiO3 (BT)-based high dielectric compositions that are promising for Y5V-type multilayer ceramic capacitors. A solid solution with a nominal composition (1− x)BaTiO3– xBa(Cu1/3Nb2/3)O3 (BCN) ( x=0, 0.025) was synthesized by conventional mixed oxide route, followed by compositional modification with varying concentration of Sn, as given by the formulation: 0.975 BaTi1− ySn yO3–0.025 Ba(Cu1/3Nb2/3)O3 ( y=0.05, 0.06, 0.075, 0.1). Room-temperature (RT) X-ray diffraction patterns showed a decrease in the tetragonality of BT after modifying with BCN (BTBCN). Modifications with Sn lead to a further decrement in tetragonality and the RT structure became cubic at 6.0 at.% doping level. The decrement in tetragonality was accompanied by lowering of Curie temperature ( Tc). BTBCN doped with 6 and 7.5 at.% Sn were found to exhibit diffuse phase transition accompanied by a high dielectric constant ≥7000, a low loss tangent ≤1% and a grain size in the submicrometer regime (≤1 μm). [ABSTRACT FROM AUTHOR]

The article presents a study that examined the synthesis of manganese ferrite (MnFe2O4) nanoparticles by applying a solvothermal method. The nanoparticles were synthesized to investigate potential types of magnetic field sensors that utilize thermal detection to quantify the changes in external magnetic field. X-ray diffraction was applied to in the structural phase analysis of the particles.

We report the dielectric and ferroelectric behavior of thick films, ∼10 µm, synthesized by aerosol deposition. The base composition of the films was selected to be 0.9Pb(Zr0.52Ti0.48)O3-0.1Pb(Zn1/3Nb2/3)O3 (PZT-PZN), which was modified with Mn to 0.9Pb(Zr0.52Ti0.48)O3-0.1Pb(Zn1/3Nb2/3) O3-0.52 wt% MnO2 (PZT-PZN-Mn) in order to induce hardening. The polarization dynamics of the synthesized films was modeled using the theory developed for magnetic glassy systems. It was found that the substitution of Mn significantly (1) enhances the relaxation time, (2) reduces the magnitude of dielectric constant and dielectric loss, and (3) enhances the internal bias field. The results indicate the presence of domain wall pinning by the formation of defect dipoles. [ABSTRACT FROM AUTHOR]