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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]

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 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]

Piezoelectric materials enable the conversion of mechanical energy into electrical energy and vice-versa. Ultrahigh piezoelectricity has been only observed in single crystals. Realization of piezoelectric ceramics with longitudinal piezoelectric constant (d33) close to 2000 pC N-1, which combines single crystal-like high properties and ceramic-like cost effectiveness, large-scale manufacturing, and machinability will be a milestone in advancement of piezoelectric ceramic materials. Here, guided by phenomenological models and phase-field simulations that provide conditions for flattening the energy landscape of polarization, a synergistic design strategy is demonstrated that exploits compositionally driven local structural heterogeneity and microstructural grain orientation/texturing to provide record piezoelectricity in ceramics. This strategy is demonstrated on [001]PC-textured and Eu3+-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) ceramics that exhibit the highest piezoelectric coefficient (small-signal d33 of up to 1950 pC N-1 and large-signal d33* of ≈2100 pm V-1) among all the reported piezoelectric ceramics. Extensive characterization conducted using high-resolution microscopy and diffraction techniques in conjunction with the computational models reveals the underlying mechanisms governing the piezoelectric performance. Further, the impact of losses on the electromechanical coupling is identified, which plays major role in suppressing the percentage of piezoelectricity enhancement, and the fundamental understanding of loss in this study sheds light on further enhancement of piezoelectricity. These results on cost-effective and record performance piezoelectric ceramics will launch a new generation of piezoelectric applications. [ABSTRACT FROM AUTHOR]

We report an ultra-low start-up speed windmill that consists of a 72 mm diameter horizontal axis wind turbine rotor with 12 alternating polarity magnets around its periphery and a 60 mm × 20 mm × 0.7 mm piezoelectric bimorph element having a magnet at its tip. This wind turbine operates at very low Reynolds number of around 2×104, but still it has reasonably high power coefficient of about 11% at the optimal tip speed ratio of 0.7. It was found to produce peak electric power of 450 μW at the rated wind speed of 4.2 mph. An extremely low start-up wind speed of 2.4 mph was achieved by operating the bimorph in actuator mode. [ABSTRACT FROM AUTHOR]

The determination of complex elastic, piezoelectric, and dielectric coefficients of piezoelectric ceramics is important for precision engineering devices. Here, a novel method for determining the optimal material coefficients is presented. This method minimizes the average relative error in the values of conductance, susceptance, resistance, and reactance obtained from the 1-D model in the IEEE Standard (ANSI/IEEE Std 176-1987) and the experimental measurements of the first and second radial modes. Poisson’s ratio is assumed to be a complex number in addition to the elastic, piezoelectric, and dielectric coefficients in the present method. The global minimum of the average relative error is found by searching the minimum among all local minima of the average relative error, which are obtained with the Levenberg–Marquardt modification of Newton’s method from randomly chosen initial conditions. The optimal material coefficients of an APC 850 disk and an APC 855 disk are calculated with this method. The uncertainties in the optimal material coefficients are evaluated by calculating the minimum average relative error when the real or imaginary part of each coefficient is prescribed. [ABSTRACT FROM AUTHOR]

[001]-textured Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) ceramics were synthesized by using templated grain growth method. Significantly high [001] texture degree corresponding to 0.98 Lotgering factor was achieved at 1 vol. % BaTiO3 template. Electromechanical properties for [001]-textured PMN-PT ceramics with 1 vol. % BaTiO3 were found to be d33 = 1000 pC/N, d31 = 371 pC/N, &eh;r = 2591, and tanδ = ∼0.6%. Elastoelectric composite based modeling results showed that higher volume fraction of template reduces the overall dielectric constant and thus has adverse effect on the piezoelectric response. Clamping effect was modeled by deriving the changes in free energy as a function of applied electric field and microstructural boundary condition. [ABSTRACT FROM AUTHOR]

0.8 Pb(Zr0.52Ti0.48)O3-0.2 Pb(Zn1/3Nb2/3)O3 (PZT-PZN) and 2 mol% Mn-doped PZT-PZN ceramics were investigated to deterministically identify the presence and effect of the secondary phase in controlling electrical properties. On the basis of the X-ray diffraction and energy dispersive spectroscopy analysis, we show that secondary phase in Mn-doped PZT-PZN is not MnO2 precipitate, but it is related to the formation of ZnO. This result was found to be consistent with the grain growth observed in the Mn-doped sintered ceramics and changes in ferroelectric behavior. We propose that Mn3+ substitution on Ti and Zr site induces hardening effect, whereas Mn2+ substitution on Zn-site stabilizes the perovskite phase in synthesis of PZT-PZN. [ABSTRACT FROM AUTHOR]

<001>-textured 0.675Pb(Mg1/3Nb2/3)O3-0.325PbTiO3 (PMN -32.5PT) ceramics were synthesized through templated grain growth method using BaTiO3 (BT) platelets as templates. A systematic investigation was conducted on delineating the texture development and microstructure evolution as a function of heat-treatment conditions. It was found that BT has very good stability in PbO-rich PMN-PT environment. A high texture degree of 90% was achieved using 5 vol% BT. Dielectric, ferroelectric, and piezoelectric properties were measured to understand the influence of sintering time, texture degree, and BT heterogeneity on the electrical characteristics. It was found that with increasing sintering time and texture degree, the piezoelectric constant d33 increases while the dielectric constant decreases, resulting in about 50% improvement of g33 as compared with random ceramics. Unipolar strain-field measurements of textured ceramics exhibited 0.27% strain at 30 kV/cm. The changes in large-signal response of textured ceramics were more obvious than small-signal measurement, indicating that <001> crystallographic texture enhances the piezoelectric response due to favorable domain configuration. Using the textured sample, a magnetoelectric laminate was fabricated and characterized for low magnetic-field sensitivity. [ABSTRACT FROM AUTHOR]

This study provides comprehensive analysis of the structure-performance relationships in cantilever-type piezoelectric energy harvesters. It provides full understanding of the effect of all the practical global control variables on the harvester performance. The control variables considered for the analysis were material parameters, areal and volumetric dimensions, and configuration of the inactive and active layers. Experimentally, the output power density of the harvester was maximum when the shape of the beam was close to a square for a constant bending stiffness and a fixed beam area. Through analytical modeling of the effective stiffness for the piezoelectric bimorph, the conditions for enhancing the bending stiffness within the same beam volume as that of a conventional bimorph were identified. The harvester configuration with beam aspect ratio of 0.86 utilizing distributed inactive layers exhibited an giant output power of 52.5mW and power density of 28.5mWcm-3 at 30 Hz under 6.9ms-2 excitation. The analysis further indicates that the trend in the output power with varying damping ratio is dissimilar to that of the efficiency. In order to realize best performance, the harvester should be designed with respect to maximizing the magnitude of output power. [ABSTRACT FROM AUTHOR]

Crystallographic grain-oriented ceramics (also referred to as textured ceramics) are known to exhibit a high soft piezoelectric response. However, the role of texturing in hard piezoelectric materials is not well understood and it has been difficult to obtain a balance of hard and soft properties in the same material. Here, we investigate the hard and soft piezoelectric behavior of [001]PC-textured 0.05Pb(Mn1/3Sb2/3)O3-0.95[0.4Pb(Mg1/3Nb2/3)O3-0.25PbZrO3-0.35PbTiO3] (PMnS-PMN-PZT) ceramics to illustrate the influence of texturing degree. The results demonstrate that textured PMnS-PMN-PZT ceramics exhibit a 170% higher longitudinal mode piezoelectric coefficient (d33) with only 16% reduction in the mechanical quality factor (Qm). Random PMnS-PMN-PZT ceramics were found to exhibit a d33 of 259 pC/N and a Qm of 982, while textured ceramics sintered at the same temperature demonstrated a d33 of 445 and a Qm of 824. Electric field dependent x-ray diffraction is utilized to confirm the existence of internal bias generated from defect dipoles, providing the signature for hard behavior. Temperature dependent measurement of d33 and Qm for textured PMnS-PMN-PZT ceramics indicated high stability up to 120 °C. [ABSTRACT FROM AUTHOR]

We present a general rule for the perovskite oxide ceramics: “A large piezoelectric constant in ABO3 perovskite ceramics can be obtained by tuning the weight ratio of A and B sites, WA/WB or WB/WA, to 3. Piezoelectric constant decreases significantly when WA/WB or WB/WA is in the range of 0.5–2.0, termed as forbidden zone.” A comparative analysis was conducted for broad range of materials demonstrating the applicability of proposed rule. Further based on this rule optimized compositions in BaTiO3 and alkali niobate based systems were developed. Polycrystalline ceramics in modified BaTiO3 system were found to exhibit longitudinal piezoelectric coefficient (d33) of 330 pC/N, while alkali niobate ceramics showed d33 of 294 pC/N. [ABSTRACT FROM AUTHOR]

In this study, we present a broadband magnetoelectric (ME) sensor design comprising of Metglas and piezoelectric ceramic laminate composite. A systematic study was conducted to elucidate the role of various composite variables toward the ME response [longitudinal-transverse (LT) mode] over the applied range of magnetic dc bias. The broadband behavior was characterized by flat ME responses over a wide range of magnetic dc bias at frequency of 1 kHz. The variation in ME coefficient as a function of magnetic dc bias was found to be significantly dependent on the size and shape of the laminate composites, the number of Metglas layers, and composite structure of sandwich versus unimorph. By adjusting these variables, we were able to achieve near-flat ME response over a magnetic bias range of 90–220 Oe. ME coefficient was also measured as a function of frequency, and at electromechanical resonance the peak value was found to be almost independent of applied magnetic bias in the range of 90–220 Oe. [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]

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]

〈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: 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]

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.

In this manuscript, we investigate the sintering behavior of (K,Na)NbO3 (KNN)-based ceramics covering unmodified KNN, (K,Na,Li)NbO3 (KNLN), and KNLN– xBaTiO3 (KNLN–BT) systems. Three stages of sintering were identified using detailed temperature and time dependent microscopy. The first stage corresponds to rearrangement of random shape particle to form stack of plate type particles. The second stage is characterized by rapid grain growth promoted by formation of liquid phase. The liquid phase was identified to be Na-deficient composition. In the final stage of sintering, densification slows and microstructural coarsening becomes the dominant process. The fraction control of liquid phase was an important factor to obtain dense and uniform microstructure by completely filling the voids between the plate-shaped particle stacks. [ABSTRACT FROM AUTHOR]

(Na0.5K0.5)NbO3 ceramics require sintering below 1,000oC to avoid the problem of Na-volatilization which results in lower resistivity. In this study we report the effect of CuO on the sintering behavior of (Na0.5K0.5)NbO3 ceramics. It was found that (Na0.5K0.5)NbO3+ 1.5 mol% CuO ceramics sintered at 950 °C for 2 hr exhibit excellent piezoelectric properties of d33 = 100 pC/N, kp = 0.36, and Qm = 1200. The remanent polarization and coercive field of this composition were of the order of 21.94 μ C/cm2 and 1.2 kV/mm. These results are very promising for the hard lead free piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

Hard piezoelectrics with high dielectric and piezoelectric constants are used for high-power applications. However, the sintering temperature of these ceramics is high, around 1200°C, restricting the usage of cheap base metal electrodes in fabrication of multi-layer components. This study investigates the effect of CuO and ZnO on the sintering temperature of a hard piezoelectric, APC 841, which is a MnO2- and Nb2O5-modified PZT. The addition of CuO decreased the sintering temperature through the formation of a liquid phase. However, the piezoelectric properties of the CuO-added ceramics sintered at ≤950°C were lower than the desired values. The addition of ZnO resulted in a significant improvement in the piezoelectric properties. This enhancement was attributed to the formation of a homogeneous microstructure with large grains. The APC 841+0.2 wt% CuO+1.1 wt% ZnO ceramics sintered at 950°C showed excellent piezoelectric and dielectric properties with values of kp=0.532, Qm=750, d33=351 pC/N, ℇ33/ℇo=1337, and Tc=280°C. [ABSTRACT FROM AUTHOR]

This study demonstrates the integrated approach based upon texturing and acceptor doping for realizing a high-power piezoelectric ceramic with combined soft and hard properties. The textured Mn-doped 0.24 Pb(In 1/2 Nb 1/2)O 3 -0.42 Pb(Mg 1/3 Nb 2/3)O 3 -0.34 PbTiO 3 (PIN-PMN-PT) ceramic exhibits enhanced piezoelectric coefficient d 33 and electromechanical coupling factor k 31 in comparison with random counterpart. This enhanced piezoelectric response originates from the combined intrinsic high piezoelectric properties of <001>-oriented grains, and reduced energy barrier for polarization rotation in textured ceramics. The BaTiO 3 (BT) template in textured ceramics increases the tetragonality degree which results in improved coercive field E c but decreased mechanical quality factor Q m in comparison with random counterpart. The decreased Q m values of textured ceramics are related to the crystallographic dependence of Q m and the enhanced domain mobility due to the existence of small size domains. The textured ceramic with 2 vol.% BT content exhibited an excellent combination of soft and hard piezoelectric properties, measured to be: d 33 = 517 pC/N, Q m = 1147, E c = 10.0 kV/cm, and tan δ = 0.49%, which is highly promising for high power piezoelectric applications. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The ferroelectric, ferromagnetic, and magnetoelectric properties of (1-x) Pb(Zr0.52Ti0.48)O3–xNiFe1.9Mn0.1O4 (PZT-NFM) ceramic composites were found to be dependent upon postsinter annealing and aging. It was found on annealing and aging that (i) the size and density of the NFM phase is reduced, (ii) the PZT lattice constants changed from (a=3.87 Å, c=4.07 Å) to (a=4.07 Å, c=4.09 Å), (iii) the ferroelectric and ferromagnetic Curie temperatures decreased by 8 and 33 °C, respectively, and (iv) the magnetoelectric coefficient increased by ∼50%. [ABSTRACT FROM AUTHOR]

Abstract: Highly dense magnetoelectric composite films with 10μm-thick of high piezoelectric voltage coefficient material, 0.9Pb(Zr57Ti43)O3–0.1Pb(Mn1/3Nb2/3)O3 (PZT–PMnN) and magnetostrictive material, Ni0.8Zn0.2Fe2O4 (NZF), were fabricated on a platinized Si substrate using aerosol deposition (AD). With increasing magnetic NZF content, dielectric and ferroelectric properties were gradually decreased while magnetizations were improved. The 20% NZF added composite thick film were found to exhibit the maximum ME coefficient. This optimal NZF content is the same as that of bulk ME composite materials. It is noticeable that AD can control the content ratio of ME composite films by controlling the powder composition. The fabricated ME composite films have high ME voltage coefficient coupling because of high density without severe inter-reactions of two phases. [Copyright &y& Elsevier]