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Rising demands in design of metamaterials requires better understanding of coupling phenomena in composite systems. Materials exhibiting product properties have effective magnitude of physical constants surpassing those of naturally existing materials. In this manuscript, we conduct numerical modeling of laminated terfenol-D/PZT/terfenol-D magnetoelectric composites with sandwich structure coupled through elastic interactions across the bonding layer. Developed magnetoelectric model couples the piezoelectric and magnetostriction constitutive equations with Langevin theory for simulating the saturated elastic response in composites. Simulated results were found to be in good agreement with the experimental results. Based upon the developed model we predict 17% improvement of magnetoelectric coefficient for sandwich structure through proper rotation of polarization in individual layers. [ABSTRACT FROM AUTHOR]

We report the success in fabricating clamped, “island,” and freestanding 10 μm thick piezoelectric films using aerosol deposition. The deposition was conducted at room temperature by impinging the piezoelectric particles flowing through the nozzle onto platinized silicon (Pt/Ti/SiO2/Si) substrate and crystallization was conducted by annealing at 700 °C. Freestanding films were synthesized by increasing the cooling rate from annealing temperature to room temperature which resulted in large internal stress between the substrate and film interface. Dielectric and ferroelectric characterizations showed enhanced ferroelectric performance of freestanding films as compared to continuous or clamped film which was associated to increased domain contribution due to decrease in degree of clamping as further confirmed by piezoforce microscopy. [ABSTRACT FROM AUTHOR]

By using coarse graining model, the dependence of magnetoelectric (ME) coupling on the mutual orientations of magnetic and electric fields with respect to the orientation of layers in polycrystalline multiferroic laminates is investigated. It is shown that the ME coefficient, described by polarization change in response to the applied magnetic field, is proportional to the trace of effective piezomagnetic strain tensor projected onto laminate interfaces. The piezomagnetic strain significantly depends on the orientation of applied magnetic fields. The results obtained here demonstrate that the magnetoelectric effect in layered composites can be significantly improved by optimizing the configuration of applied electric/magnetic fields. [ABSTRACT FROM AUTHOR]

This study reports the discovery of two perovskite materials Ba(Li[SUB1/4]Nb[SUB3/4])O[SUB3] (BLN) and Ba(Cu[SUB1/3]Nb[SUB2/3])O[SUB3] (BCN). BLN has a cubic symmetry at room temperature. The magnitude of dielectric constant at room temperature is of the order of 41. The dielectric spectrum of BLN exhibits a U shaped curve with a flat bottom. This flat region occurs in the temperature range of 200 - 300°C and the magnitude of dielectric constant in this region is 40 with a 0 ppm/°C temperature coefficient of permittivity. These characteristics appear to be very promising for microwave applications. BCN has a tetragonal structure at room temperature with a high tetragonality of 3.5%. The tetragonal symmetry is maintained until 600°C where the structure changes to cubic phase. Based upon the x-ray diffraction analysis, dielectric and electromechanical measurements of the BCN-PbTiO[SUB3] solid solutions it is predicted that BCN is a ferroelectric with high Curie temperature. [ABSTRACT FROM AUTHOR]

Perovskite ferroelectric xBiScO[sub 3]-yBiGaO[sub 3]-(1-x-y)PbTiO[sub 3] (BS-BG-PT) single crystals were successfully grown using the high temperature solution method. The dielectric constant (K) of tetragonal crystals at room temperature was determined to be 500-600 with dielectric loss tangents less than 0.3% at a frequency of ∼1 kHz. The Curie temperature T[sub c] was found to be around ∼420°C, with longitudinal piezoelectric coefficient of ∼300 pC/N for 〈001〉 oriented tetragonal crystals. The remnant polarization P[sub r] was 46 µC/cm² with a coercive field E[sub c] of 43 kV/cm at 1 Hz and dc field of 60 kV/cm. Based on dielectric and polarization measurements, it was found that the low frequency regime was dominated by a space charge conduction mechanism. A space charge model is developed which correlates the polarization with the dielectric relaxation. The relaxation time on the order of ∼2.2 ms was obtained in the BS-BG-PT single crystal using this model. [ABSTRACT FROM AUTHOR]

The functional form of the time decay of the remanent polarization under high-electrical drives, known as fatigue, has been derived for relaxor piezoelectric materials based on the hierarchical relaxation process, typical of disordered systems such as random-field and glassy states and is given in terms of normalized remanent polarization (&Pmacr;[sub r]) as &Pmacr;[sub r](t)=&Pmacr;[sub o]t[sup -x] exp[-c(t/τ)[sup β]]. This function was verified by fitting the dynamics of the fatigue behavior in 0.92Pb(Zn[sub 1/3]Nb[sub 2/3])O[sub 3]-0.08 PbTiO[sub 3] (PZN-PT) relaxor-based piezoelectric system. Mn modification of a PZN-PT single crystal improved the fatigue behavior by slowing down the relaxation processes and pinning the domain wall motion. [ABSTRACT FROM AUTHOR]

Polarization switching and dielectric temperature behavior have been investigated in 0.55Pb(Yb[sub 1/2]Nb[sub 1/2])O[sub 3]–0.45PbTiO[sub 3] (PYN–PT) single crystals. These compositions are of interest owing to their unusually high Curie temperature and high coercive fields. The dielectric permittivity was determined as function of temperature and the polarization was measured as a function of applied field for different drive frequencies. Analysis of the experimental results with a random-field model was found to show similar trends to recent reports for the Pb(Mg[sub 1/3]Nb[sub 2/3])O[sub 3] relaxor materials. The frequency dispersion of the maximum in dielectric spectra, T[sub max], was also analyzed with the Vogel–Fulcher relation yielding a high freezing temperature of 577 K. Polarization behavior was found to follow a stretched exponential time dependence and a fractal dimension of ∼2.2 was obtained. It is proposed that the polar cluster state in PYN-PT single crystals do not freeze in random orientations but rather arrange locally in preferred configurations. The fraction of the clusters decreases under increasing external field drive, resulting in the formation of the percolated network at higher fields. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this article, we report the dielectric and piezoelectric properties of Mn modified 0.92Pb(Zn[sub ⅓]Nb[sub ⅔])O[sub 3] - 0.08PbTiO[sub 3] (PZNT) single crystals. The crystals were grown by the modified-flux method. Mn substitution resulted in enhanced mechanical quality factor, Q[sub m], and a moderate increment in the rhombohedral to tetragonal phase transition temperature with increasing Mn composition. Investigation of the role of Mn in PZNT was performed on the basis of dielectric, piezoelectric and polarization versus electric hysteresis measurements. It was found that the improved Q[sub m] is obtained because of the induction of the "hard" characteristics into the PZNT single crystal. High Q[sub m] piezocrystals are being developed for high power applications. [ABSTRACT FROM AUTHOR]

Thermomagnetic energy harvesting technology has not received significant attention despite great potential for generating electricity from low thermal gradient near room temperature. This review summarizes the findings reported in literature covering the broad topical areas within thermomagnetic energy harvesting and provides perspective on the potential applications of this technology. The information has been organized chronologically in order to provide systematic understanding of the concepts and evolution of the device designs. Both, active and passive types of thermomagnetic energy harvesters have been included in the paper. The selection of suitable thermomagnetic material is key towards achieving an efficient energy generation device. Therefore, various material compositions have been discussed and their thermomagnetic behavior has been elucidated to provide guidance for their implementation in future devices. [ABSTRACT FROM AUTHOR]

Modeling thermoelectric generator (TEG) performances plays an important role in guiding the design of TEGs to achieve better efficiency. However, a rigorous 1-D TEG modeling performance has not yet been conducted, which prevents reliable prediction of TEG performance. In this work, a detailed 1-D model has been developed to take into account temperature-dependent thermoelectric material properties, heat loss due to radiation and conduction, and Thomson effect. A Lead Telluride (PbTe) TEG was chosen as a sample module and the modeling results agree very well with the experimental results, which proves how powerful the presented detailed 1-D model can be used to predict and validate TEG experimental results. TEG power and efficiency were found to have a respective decrease of 10% and 31% from the simplified model at a temperature gradient of 570 K. While heat loss attributable to conduction and radiation were found to be small, the Thomson effect, which is often neglected, was found to significantly reduce TEG performances. The deep analysis enabled by the new model provides useful guidelines to improve the performance of TEGs. [ABSTRACT FROM AUTHOR]

In this paper we report the dielectric and piezoelectric properties of Bi modified Ba1-xBixTiO3lead-free ceramics. These ceramic samples were synthesized by conventional solid state reaction method. The XRD spectra recorded at room temperature (RT) suggested decrease in the tetragonality (c/a) for Bi doped derivatives with the presence of minor rhombohedral phase for heavily doped specimens. The grain boundary pinning occurring in slightly Bi-doped derivative (x = 0.025) was found to reduce the grain size to submicron regime. However, for higher Bi doping the presence of liquid phase led to the grain coarsening. The doped derivatives exhibited shifting of the paraelectric-ferroelectric (PE-FE) phase transition towards RT with rather diffused Curie peak. The substitution of Bi3+(with different ionic radii and electronegativity) onA-site of ABO3structure resulted in regions with modified polar structure giving rise to diffusedPE-FEphase transition. The specimen with x = 0.025 exhibited enhanced planar electro-mechanical coupling constant (kp) ∼ 25% with longitudinal piezoelectric constant (d33) of ∼112pC/N. The sample with x = 0.025 also exhibited 0.085%electric-field induced strain along with the remnant polarization (2Pr) of ∼15μC/cm2and coercive field (2Ec) of ∼22kV/cm. The increasedEcwith reasonablePris an important material characteristics for the stable functionality of the memory devices. [ABSTRACT FROM PUBLISHER]

The shear mode piezoelectric properties of Pb(Mg1/3Nb2/3)O3-Pb(Zr,Ti)O3 (PMN-PZT) ceramic with 72% ⟨111⟩ texture were investigated. The piezoelectric anisotropic factor d 15/d 33 was as high as 8.5 in ⟨111⟩ textured ceramic as compared to 2.0 in random counterpart. The high d15/d33 indicates the "rotator" ferroelectric characteristics of PMN-PZT system and suggests that the large shear piezoelectric response contributes towards the high longitudinal piezoelectric response (d33) in non-polar direction (d33 = 1100 pC/N in ⟨001⟩ textured ceramic vs. d33 = 112 pC/N in ⟨111⟩ textured ceramic). [ABSTRACT FROM AUTHOR]

A reduced concentration of ionic defects along with >99 % of the theoretical density has been achieved for KNaNbO ceramic by employing a twofold sintering technique. Lower concentration of ionic defects resulted in an order of magnitude improvement in the resistivity and hence enhanced poling of the ceramic at 100 °C. High density and improved poling of the ceramic resulted in a significant improvement in electromechanical properties while maintaining the high orthorhombic-tetragonal ( T) and Curie ( T) temperatures of KNaNbO (200 and 395 °C respectively). A comparison with the previous studies suggested that the piezoelectric properties of the ceramic synthesized in this study were similar to those synthesized using complex techniques such as spark plasma sintering and hot pressing. This is a significant advancement facilitating the possibility of transition of KNaNbO ceramic toward device application. [ABSTRACT FROM AUTHOR]

Obtaining accurate kinematic data of animals is essential for many biological studies and bio-inspired engineering. Many animals, however, are either too large or too delicate to transport to controlled environments where accurate kinematic data can be easily obtained. Often, in situ recordings are the only means available but are often subject to multi-axis motion and relative magnification changes with time leading to large discrepancies in the animal kinematics. Techniques to compensate for these artifacts were applied to a large jellyfish, Cyanea capillata, freely swimming in ocean waters. The bell kinematics were captured by digitizing exumbrella profiles for two full swimming cycles. Magnification was accounted for by tracking a reference point on the ocean floor and by observing the C. capillata exumbrella arclength in order to have a constant scale through the swimming cycles. A linear fit of the top bell section was used to find the body angle with respect to the camera coordinate system. Bell margin trajectories over two swimming cycles confirmed the accuracy of the correction techniques. The corrected profiles were filtered and interpolated to provide a set of time-dependent points along the bell. Discrete models of the exumbrella were used to analyze the bell kinematics. Exumbrella discretization was conducted using three different methods. Fourier series were fitted to the discretized models and subsequently used to analyze the bell kinematics of the C. capillata. The analysis showed that the bell did not deform uniformly over time with different segments lagging behind each other. Looping of the bell trajectory between contraction and relaxation was also present through most of the exumbrella. The bell margin had the largest looping with an outer path during contraction and inner path during relaxation. The subumbrella volume was approximated based on the exumbrella kinematics and was found to increase during contraction. [ABSTRACT FROM AUTHOR]

Abstract: Large Scale Wind Turbines (LSWTs) have been extensively examined for decades but only few studies have been conducted on the small scale wind turbines (SSWTs) especially for low wind speed applications. This study provides the theoretical and experimental results on a 40cm diameter small wind energy portable turbine (SWEPT) with rated wind speed of 4.0m/s. The wind tunnel experiments revealed that SWEPT has rated power output of 1W and is capable of producing power output up to 2.2W at wind speed of 5.5m/s. In comparison to the published literature, SWEPT is one of the most efficient wind turbines at the small scale (rotor diameter<50cm) and very low wind speed (<5m/s). SWEPT demonstrated a power coefficient of 32% and overall efficiency of 21% at its rated wind speed. We believe that the results reported in this study will be immediately applicable for developing power sources for the wireless sensor nodes used in structural health monitoring on bridges and highways and security systems in common household. [Copyright &y& Elsevier]

We report the structural, electrical, and magnetoelectric (ME) properties of cofired ME laminate composites synthesized using tape-casting approach. Compositions corresponding to 0.2Pb (Zn1/3Nb2/3)-0.8Pb(Zr0.5Ti0.5)O3 [PZNT] and (Ni0.6Cu0.2Zn0.2) Fe2O3 [NCZF] were used as piezoelectric and magnetostrictive phases, respectively. In order to reduce the sintering temperature of the ferrite layer, NZF was modified with Cu and thereafter the laminate composite was successfully sintered at 930°C. The interface between PZNT and NCZF was found to exhibit strong bonding with no structural defects, which was correlated with cross diffusion of ions. The laminate composite was found to exhibit the ME coefficient of 82 mV · (cm·Oe)-1 at Hdc = 67 Oe and was able to detect a small DC magnetic field of 1 μT under Hac = 1 Oe at 1 kHz. This sensitivity was attributed to the effectiveness of elastic coupling in the laminate structure. Fabrication of cofired laminate composites with high magnetic field sensitivity will lead to their wide-scale application. [ABSTRACT FROM AUTHOR]

Abstract: We report the synthesis technique for fabrication of fine Pb(Zr,Ti)O3 (PZT) fibers via combination of sol–gel route and pulling method. It was found that spinning characteristics of PZT gel fibers were dependent upon the hydrolysis and molarity of the solution. Long gel fibers (meter scale) were drawn by hand-pulling method from the spinnable PZT sol. The fibers were sintered at 950°C in air atmosphere and found to exhibit dense microstructure with electrical properties similar to that of bulk. High aspect ratio and homogeneous microstructure resulted in increased mechanical flexibility of sintered fibers. [Copyright &y& Elsevier]

Abstract: Highly dense, 30μm-thick 0.95(K0.5Na0.5)NbO3–0.05BaTiO3 (KNN-BT) lead-free films were successfully fabricated on alumina substrate by aerosol deposition (AD) and the effect of Mn doping (0mol%, 0.5mol% and 1.0mol%) on the film properties was investigated. It was found that low field dielectric constant decreases by 36% for 0.5mol% Mn doping and 42% for 1mol% Mn doping. The loss factor was found to reduce by 19% for 0.5mol% Mn doping and 43% for 1mol% Mn doping. Based on the high field polarization–electric field measurement, we demonstrate that Mn induces hardening in KNN-BT thick films. The hardening is believed to be due to the pinning of the domains by dipolar defects at domain boundaries. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate synthesis, electrical and magnetic characterization of silicon carbo-nitride (SiCN) coated multiwalled carbon nanotubes in a core–shell structure. The core formed by a carbon nanotube had a diameter in the range of 10–100 nm. The shell was synthesized by pyrolysis of an SiCN precursor on the surface of carbon nanotubes. Electrical resistivity of an individual composite nanotube was measured to be ~2.55×103 Ω cm. The magnetic measurements performed by a superconducting quantum interference device on the composite nanotubes in the temperature range of 5–300 K show a reduced coercive field with increasing temperatures. The monolayer thick coating of an ultra high temperature multifunctional ceramic SiCN makes these composite nanotubes very promising for sensing applications in harsh environments. [Copyright &y& Elsevier]

The article discusses a study of the magnetoelectric (ME) effect of cofired magnetoelectric composites with partial texturing. ME effect refers to the induced electrical polarization under magnetic field or induced magnetization under electric field. It describes the process of enhancing the ME coefficient of sintered composite, as well as the process by which crystallographic texturing of piezoelectric phase can improve the piezoelectric and ferroelectric response. It cites the use of molten salt synthesis technique in fabricating the seed.

In this manuscript, we review the progress made in the synthesis of thick filmbased piezoelectric and magnetoelectric structures for harvesting energy from mechanical vibrations and magnetic field. Piezoelectric compositions in the system Pb(Zr,Ti)O3-Pb(Zn1/3Nb2/3)O3 (PZNT) have shown promise for providing enhanced efficiency due to higher energy density and thus form the base of transducers designed for capturing the mechanical energy. Laminate structures of PZNT with magnetostrictive ferrite materials provide large magnitudes of magnetoelectric coupling and are being targeted to capture the stray magnetic field energy. We analyze the models used to predict the performance of the energy harvesters and present a full system description. [ABSTRACT FROM AUTHOR]

We have developed a synthesis method of single-grain two-phase BaTiO3–(Mn0.5Zn0.5)Fe2O4 nanomaterials via a solid state reaction. The grains of BTO-rich samples were found to have a rod-like morphology with a high aspect ratio and a diameter of 200 nm, whereas the grains of MZF-rich samples had a tetrahedral/octahedral cross-section with a span of 200 nm. Such a synthesis of two-phase perovskite/spinel single-crystal grains with different grain geometries offers the potential to build new types of multiferroic materials. [ABSTRACT FROM AUTHOR]

This study investigates the variation of magnetoelectric (ME) coefficient as a function of the piezoelectric grain size in the composite system of 0.8 Pb(Zr0.52Ti0.48)O3–0.2 Ni0.8Zn0.2Fe2O4. It was found that as the piezoelectric-phase grain size increases the overall resistivity, piezoelectric, dielectric, and ferroelectric property of the composite increases and saturates above 600 nm. Below 200 nm average grain size, piezoelectric and dielectric properties decrease rapidly. The ferroelectric Curie temperature was found to decrease from 377 to 356 °C as the average grain size decreases from 830 to 111 nm. ME coefficient of the composite showed a rapid change below grain size of 200 nm and was found to saturate above 600 nm to a value of 155 mV/cm.Oe. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article about magnetoelectric composites, which appeared in the previous issue.

Dielectric and electromechanical losses play a critical role in the performance of the transducer in high power conditions. In this study, we report a systematic study on the effect of Mn-doping on the losses in the Pb(Zr x Ti1− x )O3–Pb(Zn1/3Nb2/3)O3 (PZT–PZN) system. Two types of sintering conditions were employed to synthesize ceramics with varying grain sizes. The Zr/Ti ratio in the PZT system was fixed at 52/48 corresponding to morphotropic phase boundary (MPB) and Mn concentration was varied from 0 to 0.9 wt%. The results show that the composition 0.9PZT–0.1PZN + 0.5 wt% Mn provides optimized magnitude for the dielectric, piezoelectric, and loss properties. [ABSTRACT FROM AUTHOR]

This study investigates multiple levels of impedance-matching methods for piezoelectric energy harvesting in order to enhance the conversion of mechanical to electrical energy. First, the transduction rate was improved by using a high piezoelectric voltage constant (g) ceramic material having a magnitude of g33 = 40 × 10-3 V m/N. Second, a transducer structure, cymbal, was optimized and fabricated to match the mechanical impedance of vibration source to that of the piezoelectric transducer. The cymbal transducer was found to exhibit ~40 times higher effective strain coefficient than the piezoelectric ceramics. Third, the electrical impedance matching for the energy harvesting circuit was considered to allow the transfer of generated power to a storage media. It was found that, by using the 10-layer ceramics instead of the single layer, the output current can be increased by 10 times, and the output load can be reduced by 40 times. Furthermore, by using the multilayer ceramics the output power was found to increase by 100%. A direct current (DC)-DC buck converter was fabricated to transfer the accumulated electrical energy in a capacitor to n lower output load. The converter was optimized such that it required less than 5 mW for operation. [ABSTRACT FROM AUTHOR]

Electromagnetic actuators have been commonly deployed in robotics technology for obtaining expressions and other motion. However, the current technology is unable to meet the requirement of space limitation and at the same time provide high displacement and force (22–25 mm and force 2–7 N). The loss of space due to bulky motors prohibits the possibility of installing processing and control cards inside the skull of humanoid robot which is required to realize a smart expressive face. Our study shows the feasibility of utilizing piezoelectric ultrasonic motors and fiber matrix composites as an alternative to electromagnetics. The results are very promising and clearly demonstrate the promise of piezoelectric technology. A sample skin was developed from artificial room temperature vulcanized silicone material with piezoelectric unimorphs embedded inside it. For actuation, ultrasonic motors were implemented to drive anchor points of our humanoid robot-Albert to demonstrate facial expressions like opening and closing of eyes, smiling and squinting. Characterization of macro fiber composite for both sensing and actuation was also conducted and results are highly encouraging. [ABSTRACT FROM AUTHOR]

The density of hollow particle (microballoon) filled composites called syntactic foams can be varied by two methods. The first method is the variation in microballoon volume fraction and the second method is the variation in the microballoon wall thickness, while keeping their volume fraction the same. A comparison of compressive properties of syntactic foams having microballoons of four different wall thicknesses in five volume fraction each is presented here. It is found that the compressive strength and modulus vary linearly with respect to the foam density. Dielectric constant, dielectric loss and electrical impedance are measured for four syntactic foam compositions with respect to temperature and frequency. Dielectric constant and loss are found to decrease with increase in frequency and with decrease in temperature in the range of 40–140°C. [ABSTRACT FROM AUTHOR]

This study reports a high-energy density piezoelectric polycrystalline ceramic composition in the system Pb(Zr1− xTi x)O3–Pb[(Zn1− yNi y)1/3Nb2/3]O3 (PZT–PZNN). Two different Zr/Ti ratios in the PZT system were investigated: 52/48 corresponding to morphotropic phase boundary (MPB) and 56/44 corresponding to the tetragonal phase. The compositions investigated in this study are represented as: 0.9Pb(Zr0.52Ti0.48)O3–0.1Pb(Zn1/3Nb2/3)O3 [0.9PZT (52:48)–0.1PZN]+ y wt% MnCO3, where y varies from 0 to 0.9 wt% and 0.9Pb(Zr0.56Ti0.44)O3–0.1Pb[(Zn0.8Ni0.2)1/3Nb2/3]O3 [0.9PZT (56:44)–0.1PZNN] + y mol% MnO2, where y varies from 1 to 3 mol%. A high-energy density material is characterized by the large magnitude of the product of the piezoelectric voltage constant ( g) and the piezoelectric strain constant ( d) given as ( dg). The condition for obtaining large magnitude of dg was derived to be as | d|=ℇn, where ℇ is the permittivity of the material and n is a material constant having a lower limit of 0.5. The d33. g33 value of the samples having composition 0.9 PZT (56:44)–0.1 PZNN+2 mol% MnO2 (sintered in two steps at 1100°–1000°C) was found to be 18456.2 × 10−15 m2/N, which, to the knowledge of the authors, is the highest value reported for polycrystalline ceramics. This composition was also found to exhibit a high magnitude of g33 as 83.1 V·(m·N)−1, corresponding to the magnitude of n as 1.126. [ABSTRACT FROM AUTHOR]

In this paper, aging temperature and time dependence of ferroelectric, ferromagnetic, and magnetoelectric properties of lead zirconate titanate and nickel ferrite composite (1– x) Pb(Zr0.52Ti0.48)O3– x NiFe1.9Mn0.1O4 (PZT–NFM, x=0.03, 0.05, 0.1) are reported. The magnetoelectric composites of different compositions were fabricated by using a process based on the controlled precipitation route. The processing is a combination of conventional mixed oxide sintering and thermal treatment. The thermal treatment consists of annealing at a high temperature (800°C for 10 h), followed by aging in the range of 300–400°C for 3–15 h. X-ray diffractometry patterns show variation in the amount of spinel phase with different aging temperature and time. Scanning electron microscopy investigation showed that the annealing and aging treatment increases the homogeneity of NFM in the PZT matrix. The magnitude of piezoelectric constant ( d33), piezoelectric voltage constant ( g33), and the dielectric constant exhibited significant variation in magnitude with aging time and temperature. Aging at 400°C for 5 h exhibited a maximum magnitude of d33 and g33 and minimum magnitude of dielectric constant. The magnitude of the magnetoelectric (ME) voltage coefficient (d E/d H) for 0.9PZT–0.1NFM samples sintered at 1125 °C was found to be of the order of 78 mV/cm Oe. This magnitude increased to 140 mV/cm Oe after annealing and aging at 300°C for 5 h. This significant enhancement in the magnetoelectric coefficient is probably due to the homogenization and precipitation of the spinel (NFM) phase in the perovskite matrix. [ABSTRACT FROM AUTHOR]

In this paper, the ferroelectric, ferromagnetic and magnetoelectric properties of lead zirconate titanate and nickel ferrite composite (1 - x) Pb(Zr 0.52 Ti 0.48 )O 3 -x NiFe 1.9 Mn 0.1 O 4 (PZT–NFM, x = 0.03, 0.05, 0.1) are reported. The magnetoelectric composites were fabricated using the process based on controlled precipitation route, a combination of conventional mixed oxide sintering and thermal treatment. The thermal treatment constituted of annealing at high temperature close to the calcination temperature followed by aging at lower temperatures. The phase diagram for the system PZT–NFM was not investigated in this study but an estimation of the phase fields for the PZT-rich end was conducted using the X-ray diffraction. Microstructure of the fabricated samples was analyzed using the X-ray mapping in SEM. The density of the composites sintered in the temperature range of 1100–1125°C was in the range of 7.2–7.8 gm/cm 3 , increasing with NFM content. The magnitude of piezoelectric constant (d 33 ) and the piezoelectric voltage constant decreased with increasing NFM content. The magnitude of magnetoelectric (ME) voltage coefficient (dE/dH) increased with increasing NFM content. The 0.9 PZT–0.1 NFM samples sintered at 1125°C exhibited ME coefficient of 78 mV/cm · Oe. This magnitude increased to 105 mV/cm · Oe after the thermal treatment (annealing and aging). It is expected that this enhancement is due to the change in the size of the NFM phase. [ABSTRACT FROM AUTHOR]

Bending type actuators providing high displacement (&nvsim;1 mm) with low blocking force (&nvsim;0.5 N) and the stack actuators providing low displacement (&nvsim;1 μm) with high blocking force (&nvsim;1 kN) represent the extreme ends of the current piezoelectric actuation technology. In the intermediate range there is deficiency of the actuator designs that provide high displacement with high blocking force in the frequency range of few kilohertz. This study addresses this issue and describes an actuator design “Piezo-Bow” which exhibits high displacement with high blocking force at low frequencies. The structure consist of a piezoelectric bar poled along the length with metal caps attached to the two major faces of the bar bounded by steel blocks. The piezoelectric bar is multilayered for operating at low voltages. The dimensions of the structure were optimized by FEM simulation in order to realize the resonance frequency near 2 kHz. It was observed that by changing the actuator parameters, cavity depth and cap thickness the resonance frequency can be shifted to desired frequency range. Based on the FEM analysis the optimized actuator design was fabricated. A PZT based composition corresponding to 0.98Pb(Zr 0.52 Ti 0.48 )O 3 +0.01Nb 2 O 5 + 0.01PbO was synthesized to fabricate the active actuation component. The fabricated actuator was characterized for impedance, piezoelectric constant and displacement. The experimental results were found to be consistent with the FEM analysis. [ABSTRACT FROM AUTHOR]

This study describes a multilayer piezoelectric voltage and power transformer that has one direction poling, operates in a wide-frequency range and delivers both step-up and step-down voltages by inverting the electrical connections. In this design, the input and output electrodes are on the same side of the disk and are isolated from each other by a fixed isolation gap. The electrode pattern is a ring/dot structure such that it uses radial mode for both input and output part that are built-in on the same ceramic disk. A prototype transformer was fabricated of size 15 × 2.78 mm² having mass of 3.8 gm. In the step-down configuration at the constant output power of 6 W, the transformer characteristics across a 100 Ω load were found to be efficiency = 92%, gain = 0.21 input voltage = 110 Vrms, and temperature rise = 20°C from the room temperature. In the step-up configuration at the constant output power of 5 W, the transformer characteristics across a 5 kΩ load were found to be efficiency = 97%, gain = 9.5, input voltage = 16 Vrms, and temperature rise = 8°C from the room temperature. A detailed equivalent circuit analysis of the transformer was done, and the results were found to be in excellent agreement with the experimental results. [ABSTRACT FROM AUTHOR]

This study describes a multilayer piezoelectric voltage and power transformer that has one direction poling, operates in a wide-frequency range and delivers both step-up and step-down voltages by inverting the electrical connections. In this design, the input and output electrodes are on the same side of the disk and are isolated from each other by a fixed isolation gap. The electrode pattern is a ring/dot structure such that it uses radial mode for both input and output part that are built-in on the same ceramic disk. A prototype transformer was fabricated of size 15 x 2.78 mm2 having mass of 3.8 gm. In the step-down con- figuration at the constant output power of 6 W, the transformer characteristics across a 100 11 load were found to be efficiency = 92%, gain = 0.21 input voltage = 110 Vrms, and temperature rise = 20°C from the room temperature. In the step-up configuration at the constant output power of 5 W, the transformer characteristics across a 5 kΩ load were found to be efficiency = 97%, gain = 9.5, input volt- age = 16 Vrms, and temperature rise = 8°C from the room temperature. A detailed equivalent circuit analysis of the transformer was done, and the results were found to be in excellent agreement with the experimental results. [ABSTRACT FROM AUTHOR]

This study reports the mechanism for the enhancement of resistivity in the (Ba x Sr 1 - x )(Cu 1/3 Nb 2/3 )O 3 system. In previous investigations, it has been found that the resistivity of this system decreases significantly with increasing temperature and applied electric field which inhibits the measurement of dielectric properties. The decrement in the resistivity was associated with the eutectic transformation from cuprous to cupric oxide, which occurs in the vicinity of 1075°C at a partial pressure of 0.21 atm of O 2 during sintering. It was found that by decreasing the sintering temperature to 975°C by addition of ZnO and B 2 O 3 , the resistivity of the system increases by 2 orders of magnitude. The stability under the applied field and temperature is also enhanced permitting the dielectric measurement. The dielectric constant and loss measurement as a function of temperature confirmed that this system has high Curie temperature of more than 600°C. [ABSTRACT FROM AUTHOR]

Pb(Zr,Ti)O3-Pb(Mn⅓Nb⅔)O3 (PZT-PMnN) system has been studied for high-power piezoelectric applications. This study investigates this system to find out the composition with high-power density piezoelectric characteristics and low temperature coefficient of resonance frequency (TCF). It was found that the composition 0.9PZT-0.1PMnN (Zr/Ti = 0.51/0.49) modified with 6 mol% Sr exhibits a TCF of -8 ppm/°C (-20 to +80°C). Further, the dielectric and piezoelectric properties of this composition are as follows: kp = 0.53; Qm = 800; d33 = 274; E33/F0 = 1290 and tan δ = 1.1%, which shows the suitability of this composition for ultrasonic devices used under fluctuating thermal environment. [ABSTRACT FROM AUTHOR]

We report the presence of an intermediate ferroelectric orthorhombic FE o phase in oriented 0.92Pb(Zn 1/3 Nb 2/3 )O 3 -0.08PbTiO 3 single crystals. High field-long time poling was done in order to stabilize the inherent symmetry of the crystal. Pyroelectric and dielectric measurements were conducted on <001>, <011> and <111> oriented crystals. Pyroelectric and dielectric peaks corresponding to a ferroelectric rhombohedral FE r to FE o phase transition was observed for <111> oriented piezocrystals at ∼80°C. [ABSTRACT FROM AUTHOR]

This paper reports the uniaxial and hydrostatic pressure dependence of the electromechanical property of the 0.68 Pb(Mg 1/3 Nb 2/3 )O 3 -0.32PbTiO 3 (PMNT), single crystals. A significant decrease was observed in the mechanical quality factor ( Q m ) under both uniaxial and hydrostatic pressures. This decrease was most dramatic under uniaxial conditions. The decrement in the magnitude of the Q m with pressure can be attributed to the stress induced transformation into ferroelectric tetragonal state whose c -axis is oriented at 90° from the direction of the applied stress and increased polar fluctuations within the poled piezoelectric state. The low value of Q m under uniaxial conditions may present a significant thermal stability problem under moderate drive levels. [ABSTRACT FROM AUTHOR]

Studies the effect of magnetostrictive layer on the magnetoelectric response of magnetoelectric laminate composites made from lead zirconate titanate and Terfenol-D.

In this letter, we report the dielectric and ferroelectric (FE) characteristics of potassium sodium niobate (K0.5Na0.5NbO3) single crystals grown by flux method. Orientation analysis of as-grown cubical-shaped crystals was conducted by electron backscattered diffraction technique revealing the <100> crystallographic orientation of two opposing major faces. Annealed crystals were found to exhibit FE orthorhombic to FE tetragonal transition temperature of 200 °C and Curie temperature of 407 °C. Poled <100> oriented crystals had longitudinal piezoelectric constant of 148 pC/N. Dielectric measurement as a function of temperature was conducted to determine the second order parameter in Gibbs free energy expansion. Dynamic hysteresis analysis on these crystals showed the power law relations to be of the form ∝f0.47Eo-0.85Eo1.45f0.14 and ∝f0.04Eo below and above the coercive field. [ABSTRACT FROM AUTHOR]

In this letter, we analyze the direct and converse effect in laminate composites of magnetostrictive and piezoelectric materials. Our results deterministically show that direct magnetoelectric (ME) effect is maximized at antiresonance frequency while the converse ME effect is maximized at resonance frequency of the laminate composite. We explain this phenomenon by using piezoelectric constitutive equations and combining it with resonance boundary conditions. The dominant factor controlling the position of peak ME coefficient was found to be frequency dependent capacitance of piezoelectric layer. This study will provide guidance toward the development of magnetic field sensors based on direct effect and communication components based on converse effect. [ABSTRACT FROM AUTHOR]

Quantitative relationships between processing, microstructure, and properties in textured ferroelectric polycrystals and the underlying responsible mechanisms are investigated by phase field modeling and computer simulation. This study focuses on three important aspects of textured ferroelectric ceramics: (i) grain microstructure evolution during templated grain growth processing, (ii) crystallographic texture development as a function of volume fraction and seed size of the templates, and (iii) dielectric and piezoelectric properties of the obtained template-matrix composites of textured polycrystals. Findings on the first two aspects are presented here, while an accompanying paper of this work reports findings on the third aspect. In this paper, grain microstructure evolution in the polycrystalline matrix with different template volume fractions and seed sizes is simulated. To quantitatively characterize the crystallographic texture development during templated grain growth processing, a numerical algorithm is developed to compute the diffraction peak intensities and Lotgering factor of the simulated polycrystals during grain microstructure evolution. This novel approach provides a direct link between phase field simulation and diffraction experiment. This computational study clarifies the effects of the template volume fraction and template seed size on the final grain microstructure and texture. It is found that, while the degree of crystallographic texture generally increases with increasing template volume fraction, it is the average distance between template seeds that plays an important role. This finding suggests that reducing the template seed size and shortening the seed distance is an effective way to achieve higher texture at a lower template volume fraction, which is highly desired for enhancing the piezoelectric properties of ferroelectric polycrystals. The computational results are compared with complementary experiments, where good agreement is obtained. [ABSTRACT FROM AUTHOR]

In this letter the authors report the ferroelectric and magnetoelectric (ME) properties of the cofired bilayer composite targeting low cost lead-free magnetic field sensor. The ME response was characterized as a function of the magnetic field direction and as a function of the dc bias. It was found that when the ac magnetic field is applied at 90° to the ferroelectric polarization axis of the sample, a ME response of 72 mV/cm Oe was obtained without any dc bias. The magnitude of the ME coefficient reached the saturation at dc bias of 1000 Oe having magnitude of 152 mV/cm Oe. The scanning electron microscopy analysis showed the presence of clear interface boundary between the strained BaTiO3/(Ni0.8Zn0.2)Fe2O4 region. [ABSTRACT FROM AUTHOR]

This letter reports a high energy density piezoelectric material in the system given as: Pb[(Zr0.52Ti0.48)O3]1-x[(Zn1/3Nb2/3)O3]x+yMnCO3, where x=0.1 and y varies from 0.5 to 0.9 wt %. A piezoelectric material with high energy density is characterized by a high product of piezoelectric voltage constant (g) and piezoelectric strain constant (d). The condition for obtaining large magnitude of g constant was derived to be as |d|=[variant_greek_epsilon]n, where [variant_greek_epsilon] is the permittivity of the material and n is constant having lower bound of 0.5. It was found that for all practical polycrystalline piezoelectric ceramic materials the magnitude of n lies in the range of 1.1–1.30 and as the magnitude of n decreases towards unity a giant enhancement in the magnitude of g was obtained. A two step sintering process was developed to optimize a polycrystalline ceramic composition with low magnitude of n. For the optimized composition the value of g33 and d33 was found to be 55.56×10-3 m2/C and 291×10-12 C/N, respectively, yielding the magnitude product d33·g33 as ∼16168×10-15 m2/N which is significantly higher than the reported values in literature. The magnitude of n for this composition was calculated to be 1.151. This material is extremely promising for immediate applications in the sensing and energy harvesting. [ABSTRACT FROM AUTHOR]

This letter reports a theoretical model for determination of generated electric power from piezoelectric bimorph transducers in low frequency range far from the piezoelectric resonance. The model is divided into two parts. In the first part the open circuit voltage response of the transducer under the ac stress is computed based on the bending beam theory for bimorph. In the second part, this open circuit voltage acts as the input to the equivalent circuit of the capacitor connected across a pure resistive load. The results of the theoretical model were verified by comparing it with the measured response of a prototype windmill. The prototype piezoelectric windmill consisting of ten piezoelectric bimorph transducers was operated in the wind speed of 1–12 mph. A power of 7.5 mW at the wind speed of 10 mph was measured across a matching load of 6.7 kΩ. The theoretical model was found to give very accurate prediction of the generated power and matching load and an excellent matching was found with the experimental results. [ABSTRACT FROM AUTHOR]

This letter reports a Pb(Zr[sub 0.5]Ti[sub 0.5])O[sub 3] (PZT) based composition, which provides high piezoelectric and electromechanical properties. The general form of the composition is Pb(Zn[sub 1/3]Nb[sub 2/3])[sub x](B[sub 1/3][sup I[sup ′]]B[sub 2/3][sup II[sup ′]])[sub y](Zr[sub 0.5]Ti[sub 0.5])[sub 1-x-y]O[sub 3]+0.5 wt % MnO[sub 2] (x+y=0.2). Four compositions corresponding to the earlier formulation were studied. For the composition corresponding to y=0, the radial mode coupling factor (k[sub p]) of 0.58, longitudinal mode piezoelectric constant (d[sub 33]) of 277 pC/N, dielectric constant ([variant_greek_epsilon][sub 33]/[variant_greek_epsilon][sub 0]) of 946, and mechanical quality factor (Q[sub m]) of 1402 are obtained. X-ray diffraction, dielectric, and polarization-electric field measurements were done to investigate the origin for this high performance. It was found that high soft properties are obtained due to the shifting of PZT composition towards morphotropic phase boundary and high hard properties are obtained due to the generation of dipolar defects which pin the polarization. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

High-T[sub m] relaxer materials are being developed for high-temperature high-power density electretransductien applications and high-temperature capacitors in automobile applications. A relaxer ferreelectric material of composition 0.3BiScO[sub 3]-0.6PbTiO[sub 3]-0.1Pb(Mn[sub l/3]Nb[sub 2/3]) O[sub 3] having a very high dielectric maximum of ∼350 °C is reported. The relaxer behavior is confirmed by studying polarization relaxation and frequency and temperature dependent dielectric behavior. The dielectric constant in the low-temperature region of 10 °C< T< 150 °C is found to be independent of the frequency with a temperature gradient of δε/δT= 2.5/°C. The room-temperature magnitude of dielectric constant is ∼600. [ABSTRACT FROM AUTHOR]

The dielectric and electrically induced strain characteristics of Fe-substituted Pb(Zn[sub 1/3] Nb[sub 2/3])O[sub 3]-PbTiO[sub 3] single crystals have been investigated. These investigations have shown that Fe substitution results in: (i) a lowering of the field level required to obtain large strains, (ii) an increased squareness in the ε-E response indicative of "hard" piezoelectric properties, and (iii) enhanced linearity in the region where saturation is approached at high field levels. Interestingly, the hard characteristics occur along with an enhanced stability of an intermediate ferroelectric orthorhombic state. [ABSTRACT FROM AUTHOR]

The dielectric properties of (1-χ)Pb(Mg[sub 1/3]Nb[sub 2/3])O[sub 3] - (χ)PbTiO[sub 3] (PMN-PT) crystals have been investigated over a temperature range of 4 to 450 K at various frequencies. At low temperatures, an unusual frequency dependent plateau region in the absorption was observed between 75 and 175 K. At both higher and lower temperatures, the absorption was frequency independent. Analysis of the relaxation time constant revealed power-law divergence, typical of fractal behavior in disordered magnetic systems. The results demonstrate the importance of structural irregularities on the dielectric loss mechanism in poled oriented PMN-PT crystals. [ABSTRACT FROM AUTHOR]