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Applications of Ferroelectrics, 2004. ISAF-04. 2004 14th IEEE International Symposium on

Date 23-27 Aug. 2004

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Displaying Results 1 - 25 of 95
  • The nature of large dielectric constant of relaxors

    Page(s): 143 - 148
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    Relaxors are used as non-hysteresis (electrostrictive) actuator materials applied in micromechanics and as microdrivers for microwave mechanically tunable filters and phase shifters. Displacement produced by the actuator is determined by the value of relaxor dielectric permittivity (ε). To estimate the limitations in the operation speed of relaxor-based electronic devices, the frequency dispersion of relaxor ε is studied in wide frequency range. It is assumed that dominating contribution to the relaxor material ε is electromechanical coupling of polar clusters. So the response speed of relaxor-based devices is determined by the sound speed in the relaxor material. View full abstract»

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  • Deposition of PZT thin films by hybrid process comprising sol-gel method and laser ablation for microscanners

    Page(s): 169 - 172
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    Lead zirconate titanate (Pb(Zr0.52Ti0.48)O3: PZT) thin films were prepared on Pt/Ti/SiO2/Si substrates by hybrid processing: sol-gel method and laser ablation. The preferred orientation of the PZT films obtained by the hybrid process can be controlled using the seed layer obtained by the sol-gel method. The remnant polarization and the coercive field of this film were 28.6 μC/cm2 and 58.0 kV/cm, while the dielectric constant and loss values measured at 1 kHz were approximately 1050 and 0.045, respectively. The devices of micro mirrors were successfully fabricated through the PZT film deposition, lithography cyclotron resonance (ECR), reactive ion etching (RIE) and inductively coupled plasma (ICP) releasing processes. The scanning angle was about 6±2 degrees by resonating two beams with AC 5 Vp-p at the resonance frequency of 1975 Hz. The results indicated that the piezoelectric PZT films deposited by the hybrid process have sufficient actuation capability for MEMS application. View full abstract»

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  • High temperature electrostrictive ceramics for a Venus ultrasonic rock sampling tool

    Page(s): 130 - 133
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    NASA's intended mission to Venus (the Venus In-situ Explorer) will require unprecedented advances in robotic technology suited for high temperatures and extreme environments. This paper addresses development of an ultrasonic rock drilling-coring-abrading tool to quickly sample Venus surface material for chemical analysis. The key innovation behind this device is a BiScO3-PbTiO3 piezoelectric ceramic that has been modified to have high resistivity up to 500°C. This material was found to have very good piezoelectric properties to the depoling temperature of 420°C, and at 450°C it functioned as an electrostrictor with an induced piezoelectric coefficient of ∼ 450 pC/N under a 7 kV/cm DC bias. View full abstract»

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  • Conversion of 45° rotated X-cut KNbO3 plates to Y-cut plates by compression

    Page(s): 98 - 101
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    Potassium niobate (KNbO3) single crystals with a pseudo-cubic structure exhibit very high piezoelectric coupling factors for thickness-extensional modes and surface acoustic waves, kt and kSAW. To obtain a better understanding of domain-behavior with a stress, conversion of high-kt 45° rotated X-cut plates of KNbO3 to high-kSAW Y-cut plates was attempted by applying a compressive force obliquely to the major surface of the plates. The X-ray diffraction analysis indicated that 90% of the 45° rotated X-cut plate were converted. The admittance response of the resulting plate was very close to that of a single-domain Y-cut plate. The domain evolution during application of a stress was observed and video-recorded using a developed system consisting of a polarizing microscope equipped with a stress application tool and a video camera. This observation showed that the conversion was occurred by a pressure of 6.6 MPa. View full abstract»

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  • Harmonic analysis of the polarization hysteresis loops for aged PZT

    Page(s): 213 - 216
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    Lead zirconate titanate (PZT) suffers aging, which cause its properties to deteriorate. Understanding the aging of PZT is critical to the design of devices. This work used harmonic analysis to study polarization hysteresis loops (PE-loop) of aged PZT. The results indicated that harmonics 1-5 have unique effect on the shape of PE-loops. The changing of these amplitudes and phase angles of these harmonics during aging period caused PE-loops to alter their shapes with time. View full abstract»

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  • Characterization and modeling of local electromechanical response in stress-biased piezoelectric actuators

    Page(s): 56 - 59
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    Numerous investigators have explored the factors that contribute to the high electromechanical performance of stress-biased actuators with particular attention being given to the importance of the extrinsic (domain wall translation) response mechanism. Based on the variation in lateral stress through the thickness of the piezoelectric layer within these devices, it has been suggested that the piezoelectric coefficient varies as a function of position within the layer, though no direct evidence has been previously presented. In this study, the results of Moire interferometry investigations of local strains within these devices are reviewed. The technique permits effective depth-profiling of local deformations at reasonably high (0.25 μm) resolution. A least squares regression analysis approach was used in conjunction with classical laminate theory and free edge effects to fit this experimental data to depth-dependent piezoelectric response. As expected, higher d-coefficients were predicted for the upper free surface of the device compared to the interface with the stainless steel substrate. The predicted values were in general agreement with expectation and are further considered from the perspective of recent reports in the literature regarding multi-axial loading effects on the electromechanical properties of lead zirconate titanate-based piezoelectric ceramics. View full abstract»

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  • The electrical characteristics of the (Ba0.7Sr0.3)(Ti0.9Zr0.1)O3 thin film using oxygen plasma surface treatment

    Page(s): 173 - 176
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    In this work, the effects of plasma surface treatment, using oxygen gas, of Ba0.7Sr0.3Ti0.9Zr0.1O3 (BSTZ) film on the electrical characteristic of a Al/BSTZ/Pt capacitor structure were investigated in detail. Experiment results showed that the leakage current density of the BSTZ thin film within oxygen plasma treatment was decreased as much as three times in magnitude, as compared to that of the BSTZ film without oxygen plasma treatment. In addition, the dielectric constant of BSTZ film was increased from 190 to 260 within oxygen plasma treatment. These results clearly indicated that the electrical characteristics of BSTZ film were improved effectively within oxygen plasma surface treatment. View full abstract»

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  • Templated grain growth (TGG) of PMN-PT textured components using SrTiO3 templates

    Page(s): 270 - 273
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    Tapes of PMN-PT containing 5 to 10 volume % of SrTiO3 seeds were cast and subjected to heat treatments of 1250°C in either air or oxygen atmospheres for 10 hours in order to texture the samples and enhance the (h00) peaks of PMN-PT. Lead-based additives such as lead oxide (PbO) and lead carbonate (PbCO3) were introduced to create a liquid phase during heat treatment of the samples. The effects of sintering atmosphere, sintering time, and addition of lead-based additives were studied to determine which factors resulted in the highest degree of texturing. SEM studies revealed that the grown PMN-PT regions from the SrTiO3 seeds were approximately 40-60 μm in length after proper heat treatment. XRD studies showed an enhancement in the (100) and [200] crystallographic orientations of PMN-PT. Calculated Lotgering factor (f) values indicated that the samples fabricated with 1 wt.% PbO at 1250°C for 10 hours in an oxygen atmosphere were textured up to ∼50%. View full abstract»

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  • Modelling of the poling process in functionally graded materials

    Page(s): 118 - 121
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    Materials, containing an one- or multidimensional gradient of structural or chemical properties, connected with a changing of the material properties, are called functionally graded materials (FGM). They have a high potential in a wide range of applications, for instance to improve the interface between two different materials. Moreover, new functions of materials can be created by them. Piezoelectric FGM can be used in actuator or ultrasonic applications. It is known that FGM ultrasonic transducers show a broader frequency bandwidth. There are different ways and technologies to prepare ceramics with a functional gradient. One possibility is the preparation of ceramics with a gradient of the chemical composition along the thickness direction. The chemical gradient will be transformed into a gradient of the electromechanical properties by a poling process. Usually, there is a very inhomogeneous distribution of the poling field inside the graded material due to a corresponding gradient of the dielectric coefficient. Or et al. have shown that the electric field distribution is not constant in time and depends on the electric conductivity of the used materials. Their model describes the poling process of two layer system using a modified tanh function for the ferroelectric hysteresis loop. We enhanced this model by implementation of the Preisach model, an established approach of hysteresis effects in ferromagnetics and ferroelectrics. This allows the modelling of the electric field distribution and the polarization of each layer at arbitrary applied voltages for different poling regimes as well as the time-dependent modelling of switching processes. The numerical model can be used for multilayer structures of two or more materials and is therefore a good approximation of functionally graded materials. We compare the modelling with experimental results of the measurement of the electric field distribution in multilayers based on BaTi1-xO3-BaSnxO3 ceramics, where the Sn content changes from 7.5 to 15 mol%. Additionally, the electromechanical properties were characterized by bending measurements. The results were compared with FGM ceramics with the same chemical composition. View full abstract»

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  • Paraelectric (Ba0.6Sr0.4)TiO3 thick films by direct-write

    Page(s): 21 - 24
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    MicroPen™ direct-write technique has been used to fabricate polycrystalline paraelectric BST 60/40 11-140 μm thick films on alumina substrates. The dielectric properties of the thick films were studied as a function of film thickness, microstructure, and the state of residual stresses. Sin2Ψ X-ray analyses indicated a compressive state of stress in the films which decreased from ∼40 MPa at 36 μm to ∼15 MPa at 140 μm. The cubic→tetragonal transition temperature was found to be -10°C. No thickness dependence of the transition temperature was observed. Field induced polarization curves also indicate no apparent nonlinear behavior up to 4 kV/mm. View full abstract»

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  • Modeling of the dual-output piezoelectric transformer operating at thickness shear vibration mode

    Page(s): 225 - 228
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    In our previous study, dual-output piezoelectric transformers operating at thickness shear vibration mode were proposed and experimentally investigated. By designing a new construction of support and lead wire connection, a power density of 52.7 W/cm3 and a total output power of 169.8 W were attained at a temperature rise less than 2°C. In this paper, equivalent circuit parameters of the dual-output piezoelectric transformers operating at thickness shear vibration mode were derived. Based on this the impedance characteristics, equivalent inductance, voltage gain and other characteristics of the piezoelectric transformers were calculated. Validity of the method was verified by experimental results. View full abstract»

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  • Electromechanical properties of high coupling single crystals under large electric drive and uniaxial compression

    Page(s): 64 - 69
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    This work investigates the 33-mode electromechanical response of relaxor-ferroelectric lead magnesium niobate-lead titanate (PMN-PT) single crystals when driven with large fields ∼ 0.4 MV/m (rms) under a combined dc field and mechanical bias similar to those used in the design of sonar. It demonstrates that the remarkable small signal length extensional coupling (k33>0.90) and other electromechanical properties of morphotropic PMN-PT single crystals prevail under large drive. The observed roll-off of k33 at 42 MPa is analyzed within the framework of recent structural data and the high-order Devonshire theory of possible ferroelectric-ferroelectric transition trajectories. View full abstract»

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  • Driving of 35W(T5) fluorescent lamp by the electronic ballast using piezoelectric transformer

    Page(s): 233 - 236
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    Recently, 40 W fluorescent lamps with 32 mm tube diameter are replaced with 32 W one with 26 mm in diameter to conserve lamp materials and to increase luminance efficiency. Moreover, 35, 28 and 14 W fluorescent lamps with 16 mm in diameter (T5), which are nowadays developed, also may replace 32 W lamps again. Application of slim lamps, however, requires small sized electronic ballast to fulfill the design philosophy of miniaturizing. However, the traditional magnetic ballasts operated at 50-60 Hz have been suffered from noticeable flicker, high loss, large crest factor and heavy weight In this study, in order to solve these problems, a new type of electronic ballast which is composed of rectifier, active power corrector, series resonant half bridge inverter and piezoelectric transformer was proposed for driving T5 fluorescent lamp. Contour vibration mode piezoelectric transformer with ring/dot electrode structure was fabricated to the size of 27×27×2.5 mm3 by cold isostatic pressing. Driving of piezoelectric transformer was carried out with input region for the ring electrode and output region for the dot electrode. A 35 W (T5) fluorescent lamp was successfully driven by the fabricated ballast with piezoelectric transformer. After driving the lamp for 25 min using the proposed electronic ballast, input power factor of 0.95, efficiency of 90.7%, were shown, respectively, at operating frequency of 79 kHz. And also, output power, efficiency and temperature rise of the piezoelectric transformer, 37.53 W, 92% and 25°C, respectively. View full abstract»

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  • Piezoelectric relaxation and large anisotropy of modified lead titanate ceramics

    Page(s): 217 - 220
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    In this study we investigate piezoelectric relaxation in Sm modified PbTiO3 ceramics. The piezoelectric coefficients d33 and d31 were measured by a direct quasi-static method in the temperature range from 25 to 150°C and frequency range from >0.01 Hz to 100 Hz. The results show presence of huge piezoelectric relaxation for both d33 and d31, which change by factor of nearly two (d33) and four (d31) in the examined frequency range. The two piezoelectric coefficients show qualitatively similar behavior as a function of frequency. The piezoelectric anisotropy (d33/d31 ratio) of this material is found to be both temperature and frequency dependent. The maximum anisotropy is about 20 at room temperature and at 100 Hz. It decreases as the temperature increases or frequency decreases and finally it approaches at low frequencies the value typical for that in PZT ceramics (about 3). View full abstract»

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  • Cooling-rate-dependent domain structures of PMN-PT single crystals observed by contact resonance piezoresponse force microscopy

    Page(s): 305 - 308
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    The domain structures of PMN-0.32PT single crystals were observed at the same area at room temperature after 240°C thermal treatment with various cooling rate. Contact resonance piezoresponse force microscopy was utilized for observing domain structures in order to obtain microdomain images nondestructively. The average domain size decreased as cooling rate increased. The dielectric properties in ferroelectric phase was also influenced the cooling rate. If peak temperature of thermal treatment was higher than 135°C, the dielectric constant in ferroelectric phase decreased as cooling rate increased. View full abstract»

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  • Complex rare-earth substituted lead titanate piezoceramics

    Page(s): 297 - 300
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    In this work we have investigated the properties of new compositions of Gd, Nd and a mixture of Gd+Nd -added Pb(Ti,Mn)O3 ceramics, containing a few percent of Bi, to partially substitute the lead. The samples have been prepared starting from high purity oxides by solid-state reaction of oxide powders, within the sintering range 1100-1220°C. Structural and morphological investigations were performed on poled samples. The use of X-ray diffraction together with microstructural examination by transmission electron microscopy has shown evidence for the formation of tetragonal perovskite phase. The domain structure and the lattice imperfection of the PT-type samples have been investigated by a high resolution transmission electron microscope (HRTEM). Samples with diameter 10 mm and thickness 1 mm have been employed for electrical characterization. Material coefficients have been investigated as a function of temperature. Dielectric constant and resistivity were measured with a four-wire probe also on unpoled samples in a wide temperature and frequency range. View full abstract»

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  • Artificial ferroelectricity in paraelectric superlattices

    Page(s): 39 - 42
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    SrZrO3/SrTiO3 (SZO/STO) artificial superlattices were fabricated on STO substrates by the molecular beam epitaxy. The lattice distortion in the superlattices is dependent on stacking periodicity and is maximum in the [(SZO)10/(STO)10]4 superlattice. The dielectric properties were measured using interdigital electrodes at frequencies up to 110 MHz, and dielectric relaxation was observed in the [(SZO)1/(STO)1]40 and [(SZO)10/(STO)10]4 superlattices in the low-frequency domain. The dielectric permittivities of all superlattices were more than 10,000 at 110 MHz. The charge vs voltage (Q-V) measurement revealed that the SZO/STO superlattices show distinct hysteresis curves, which indicated that ferroelectricity is induced by the superlattices. The origin of the ferroelectricity seems to be related to the anisotropic lattice distortion incorporated into the superlattice structure. View full abstract»

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  • Phenomenological and structural studies of the morphotropic phase boundary in lead zinc niobate (PZN)-lead titanate (PT)

    Page(s): 209 - 212
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    Unknown dielectric stiffness coefficients in the elastic Gibbs free energy for Pb(Zn13/Nb23/)O3-PbTiO3 (PZN-PT) binary solid solution with monoclinic phase were estimated by fitting the calculated phase diagram with the available experimental one. The connecting coefficients of polarization of tetragonal and rhombohedral in a spontaneous polarization were determined by fitting the temperature change of lattice parameters in 0.91PZN-0.09PT to the calculated one. The calculated PZN-PT phase diagram using the newly estimated dielectric stiffness coefficients was in good agreement with the experimental one. The dielectric constants could be calculated at the composition near the MPB in PZN-PT. View full abstract»

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  • Microstructure and piezoelectric properties of <001> fiber textured Pb(Mg13/Nb23/)O3-34.5PbTiO3 ceramics

    Page(s): 157 - 160
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    Textured PMN-PT ceramics were synthesized by homo-template grain growth (HTGG) using PMN-PT nano-particles and cubic single crystal templates (50 μm). Samples are prepared using doctor Blade method and sintered in PbO controlled atmosphere. Orientation of the templates was obtained during tape casting. Textured tape cast ceramics display quasi complete [001] texture (f=0.99) in the cubic phase. The (111) pole figure reveals [001] fiber texture in accordance with optical observation. The texture was obtained in all the volume and only small orientation distribution (<6°) was observed. Smart Raman imaging shows that the final composition is very close to that of the matrix. Piezoelectric properties measured at low level using RIE method show that coupling efficiency of tape cast textured ceramics (kp =0.69, d33= 600pC/N) are about twice of tape cast random ceramics but only ∼20% better than random optimized disk ceramic. Regarding low orientation distribution of the high textured ceramics, we conclude that poling process and ferroelectric domain reorganization have to be extensively studied to clarify behavior of textured ceramics. View full abstract»

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  • Piezoelectric anisotropy - phase transition relations in perovskite single crystals

    Page(s): 110 - 113
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    The orientation dependence of the longitudinal piezoelectric coefficient is investigated as a function of temperature in BaTiO3 and PbTiO3 crystals using Landau-Ginsburg-Devonshire theory. We show that a presence of the ferroelectric - ferroelectric phase transitions in BaTiO3 leads to an enhanced piezoelectric longitudinal response along nonpolar directions. The reason for this is the abrupt increase of the shear piezoelectric coefficients in the vicinity of a FE - FE phase transition temperature. In PbTiO3, which does not exhibit such phase transitions, the shear piezoelectric effect is weak and the longitudinal piezoelectric coefficient has its maximum along the polar axis at all temperatures. These results can be generalized to include phase transitions induced by electric-field and composition variation and are valid for all perovskite materials. Further, using Landau-Ginzburg-Devonshire theory and tetragonal BaTiO3 as an example, we demonstrate that a strong electric bias fields applied anti-parallel to the spontaneous polarization may lead to a large enhancement of piezoelectric properties in monodomain perovskite crystals. The enhancement is due to the field-induced dielectric softening of the crystal. View full abstract»

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  • Influence of processing conditions on the morphotropic phase boundaries and ferroelectric properties of Pb(Zn13/Nb23/)O3-Pb(Ni13/Nb23/)O3-Pb(Zr12/Ti$ d12/)O3 solid solutions

    Page(s): 274 - 277
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    Ceramic solid solutions within the ternary system of Pb(Zn13/Nb23/)O3-Pb(Ni13/Nb23/)O3-Pb(Zr12/Ti$ d12/)O3 (PZN-PNN-PZT) were synthesized via two methods: the mixed oxide method and the columbite method. Phase development of the calcined powders and the crystal structure of sintered ceramics were analyzed by X-ray diffraction. The ferroelectric properties of the ceramics were characterized by a combination of dielectric and hysteresis measurements. It was observed that for the binary systems PZN-PZT and PNN-PZT, the change in the transition temperature (Tm) is nearly linear with respect to the PZT content. Ferroelectric properties were analyzed to elucidate the nature of the phase transformation and identify the impact of the processing conditions. With these data, ferroelectric phase diagrams were derived showing the transition between the pseudo-cubic relaxor behavior of PZN and PNN to the tetragonal normal ferroelectric behavior of PZT. This transition was also correlated to changes in the diffuseness parameter δγ When comparing ceramics prepared by the columbite method and the mixed oxide route, ceramics prepared by the mixed oxide method showed a lower remanent polarization Pr and a higher coercive field Ec. Additionally, ceramics prepared by the columbite method displayed sharp transitions in ferroelectric properties across the MPB composition, whereas these transitions were obscured in ceramics prepared by the mixed oxide method. It is proposed that the different reaction paths influenced the degree of compositional heterogeneity in these complex perovskite solid solutions, which was clearly reflected in the nature of the phase transition. View full abstract»

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  • Enhanced piezoelectric properties of KNbO3 crystals by domain engineering

    Page(s): 221 - 224
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    Potassium niobate (KNbO3) single crystals were grown by a TSSG method. At first, the electric field was applied along [001]c (cubic notification system) direction of KNbO3 crystals to induce the engineered domain configurations into KNbO3 crystals. Prior to domain engineering, the piezoelectric properties of [001]c oriented KNbO3 single domain crystals were measured. These measurement values were completely consisted with the calculated apparent d31 and d32. Finally, the engineered domain configurations were induced into KNbO3 crystals. As a result, piezoelectric properties increased with decreasing domain sizes of the engineered domain configuration. However, the symmetry of the KNbO3 crystals was mm2, and there were four kinds of domain structures such as 90°, 180°, 60° and 120° domains. Thus, the engineered domain structure induced in this study was very complicated, and the piezoelectric properties were also depended on domain pattern and kinds of domain walls. View full abstract»

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  • Temperature- and electric-field-dependent phase transformations in [001]-oriented Pb(Mg13/Nb23/)0.6Ti0.4O3 single crystal

    Page(s): 89 - 94
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    Temperature- and electric (E)-field-dependent phase transformations in a [001]-oriented Pb(Mg13/Nb23/)0.6Ti0.4O3 (PMNT40%) single crystal have been investigated by temperature- and frequency-dependent dielectric permittivity and polarizing microscopy. The permittivity ε' exhibits a maximum near 463 K with a shoulder near 446 K and a broad step near 270 K. By using relations of crystallographic symmetry and optical extinction, polarizing microscopy data show that the unpoled crystal has tetragonal (T) phase domains with polarizations P along the [100] and [010] axes. These domains are 15 to 60 microns wide, and are separated by 90° domain walls. They coexist at 200 K with a small fraction of monoclinic (M) phase. As temperature increases toward room temperature, the T phase domain increases rapidly at the expense of the M phase. This may account for the broad peak in ε' and decrease in ε" near 270 K. The whole crystal becomes cubic near 464 K The E-field-dependent polarizing microscopy results at room temperature show that the polarizations begin to rotate to the tetragonal [001] (T001) direction through the M phase and significantly change near E=11 kV/cm. As E field increases, the crystal exhibits more T001 domain, which is associated with optical extinction at every orientation of the perpendicularly crossed polarizer/analyzer pair. The crystal becomes entirely T001 monodomain near E=33 kV/cm. After the E field is removed, the domain structure shows irreversible behavior. It does not reestablish the broad T100 and T010 domains described above, but the extinction pattern is consistent with tetragonal microdomains. View full abstract»

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  • Direct-write of PZT thick films

    Page(s): 250 - 253
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    Lead zirconate titanate (PZT) thick films have been prepared on alumina substrates using a direct-write technology. Thick films of 50 to 200 μm were deposited, dried and then sintered at 1000° to 1200°C for 30 minutes in PbO-rich atmosphere. Comparison of the thick film properties revealed that the dielectric constant and remnant polarization of the films sintered at 1100°C were maximum, likely due to a balance between densification and lead loss. The effects of three sintering aids, i.e., lead oxide, lithium bismuth oxide, and a borosilicate glass, have been investigated on the microstructure and electrical properties of the PZT thick films. It was observed that a 2 wt% lithium bismuth oxide additive has a positive effect on the dielectric constant and remnant polarization of the PZT thick films sintered at 1100°C. The microstructures of the films revealed that 3 wt% additives would result in excessive shrinkage and formation of large pores and cracks at a sintering temperature of 1100°C and above. PZT films with 2 wt.% lithium bismuth oxide showed improved dielectric constant (∼40-50%) and remanent polarization (∼65%) compared to additive-free PZT thick films. It was also found that the properties are strongly thickness dependent. View full abstract»

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  • FEM modeling of electro-elastic field in ferroelectric crystal with domain boundaries

    Page(s): 106 - 109
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    The parameters of ferroelectric thin layers are closely related to properties of materials from which they are made. Electric and elastic fields have large influence on important properties of discussed materials. The paper describes an application of the finite element method in modelling of electric and elastic fields in ferroelectric crystals and their influence on the shifts of domain boundaries. The boundary in ferroelectrics is idealized as two-dimensional defect in an electroelastic continuum, which represents the source of inhomogenity and internal distortion in both elastic and dielectric fields. The presented paper contains a derivation of the numerical model of the problem, based on the physical description of piezoelectric continuum, finite element formulation and some application of model. View full abstract»

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