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Phase Boundary (phase + boundary)
Selected AbstractsControl of Crystal Orientation and Piezoelectric Response of Lead Zirconate Titanate Thin Films Near the Morphotropic Phase BoundaryJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2002Ken-ichi Kakimoto PbZr0.53Ti0.47O3 (PZT) thin films with various preferred crystallographic orientations were synthesized on various substrates using pulsed laser deposition techniques. Larger piezoelectric displacement, which involved the bending vibration of the PZT film/substrate, was observed in randomly oriented PZT thin film than that in (100)- and (111)-preferred texture films. This result was discussed by correlation with the number of effective spontaneous polarization axes in the morphotropic phase boundary of the PZT system. Moreover, polarization fatigue was found to lower the electric-field-induced displacement significantly, indicating a large contribution of ferroelectric domain motion to the piezoelectric response of PZT thin films under bipolar drive. [source] Morphotropic Phase Boundary in the Pb(Zn1/3Nb2/3O3)-BaTiO3 -PbTiO3 SystemJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2001Weizhong Zhu The morphotropic phase boundary (MPB) in the relaxor ferroelectric system Pb(Zn1/3Nb2/3O3)-BaTiO3 -PbTiO3 (PZN-BT-PT) with 15 mol% BT was investigated through dielectric permittivity and high-temperature X-ray diffraction measurements. It was revealed that MPB is a broad composition region extending from 12 to 18 mol% PT, within which the temperatures of the permittivity maximum are close to the ending temperatures for the phase transformation from coexisting rhombohedral and tetragonal phases to cubic phase on heating. When the specimen is cooled, the starting temperatures for the rhombohedral-to-tetragonal phase transition increase with increasing PT content. The large thermal hysteresis observed by X-ray diffraction is caused by the phase transformation between rhombohedral and tetragonal phases. On cooling, the MPB curves toward the PT-rich side, so that ceramics within this composition range undergoe successive phase transitions from cubic to rhombohedral and from rhombohedral to tetragonal phase. The diffuseness of the paraelectric-to-ferroelectric phase transition is remarkably decreased by the addition of PT. The enhanced dielectric permittivity peak values for the MPB compositions are correlated with the reduced lattice distortion and phase coexistence. [source] Electric field-enhanced transport across phase boundaries and membranes and its potential use in sample pretreatment for bioanalysisELECTROPHORESIS, Issue 5 2010Pavel Kubá Abstract Separation techniques, such as electrodialysis, electroextraction, electro-membrane extraction and extraction across phase interfaces, are reviewed and discussed as methods for sample cleanup and preconcentration. This survey clearly shows that electromigration of ionic species across phase interfaces, especially across supported liquid membranes, may be very selective and is strongly dependent on the chemical composition of these interfaces. Thus, electric field-enhanced transport across chemically tailored liquid membranes may open new perspectives in preparative analytical chemistry. This review offers comprehensive survey of related literature and discussion of the topic, which may stimulate interest of experts and practitioners in bioanalysis. [source] Analysis of Tin Diffusion in Zircaloy-4 and Tin Redistribution after Steam Oxidation by Means of X-ray Fluorescence Measurements,ADVANCED ENGINEERING MATERIALS, Issue 6 2009Mirco Grosse The temperature dependence of tin diffusion coefficients in the nuclear fuel rod cladding tube material Zircaloy-4 is determined in the range of 1,000,1,400,°C by means of X-ray fluorescence measurements. During oxidation at these temperatures, tin is redistributed, as shown in the figure. Due to tin diffusion in zirconium being much slower than the growing of the oxide layer, tin is segregated inside the oxide layer and at phase boundaries. [source] Microstructure-Lattice Thermal Conductivity Correlation in Nanostructured PbTe0.7S0.3 Thermoelectric MaterialsADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Jiaqing He Abstract The reduction of thermal conductivity, and a comprehensive understanding of the microstructural constituents that cause this reduction, represent some of the important challenges for the further development of thermoelectric materials with improved figure of merit. Model PbTe-based thermoelectric materials that exhibit very low lattice thermal conductivity have been chosen for this microstructure,thermal conductivity correlation study. The nominal PbTe0.7S0.3 composition spinodally decomposes into two phases: PbTe and PbS. Orderly misfit dislocations, incomplete relaxed strain, and structure-modulated contrast rather than composition-modulated contrast are observed at the boundaries between the two phases. Furthermore, the samples also contain regularly shaped nanometer-scale precipitates. The theoretical calculations of the lattice thermal conductivity of the PbTe0.7S0.3 material, based on transmission electron microscopy observations, closely aligns with experimental measurements of the thermal conductivity of a very low value, ,0.8,W,m,1,K,1 at room temperature, approximately 35% and 30% of the value of the lattice thermal conductivity of either PbTe and PbS, respectively. It is shown that phase boundaries, interfacial dislocations, and nanometer-scale precipitates play an important role in enhancing phonon scattering and, therefore, in reducing the lattice thermal conductivity. [source] Phase transitions and heat conduction in post-glacial reboundGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2002M. E. Tamisiea Summary We have developed a method for including phase boundary conditions into post-glacial rebound models that allows for conduction of latent heat away from the boundary. This method returns the chemical boundary results if latent heat conducts away from the phase boundary too slowly to allow the transition to proceed, as is commonly argued. This is not necessarily the case, however. For example, the secular change of the geoid and the vertical uplift rates for phase boundaries with latent heat conduction can differ from the chemical boundary results by up to 10 and 15 per cent, respectively. When modelling the phase transition, we consider two scenarios: the latent heat is released either at a narrow boundary that separates the two phases or over a thick mixed region of the two phases. In the case where the phase transition occurs over a thick enough region (5,10 km), the final results are close to the results obtained by considering a phase boundary that ignores the release of latent heat completely. This thick boundary formulation also suggest that the phase boundaries could respond nearly instantaneously, changing both the elastic load and body Love numbers. However, we have not considered kinetics, the energetics of the mechanisms of the phase transitions, in this formulation. This work suggests a greater knowledge of the kinetics near equilibrium phase transitions is required. A naive calculation indicates that the kinetics will not be a significant factor for post-glacial rebound but will be a limiting factor for earth tides. [source] Experimental Study of the Aging and Self-Healing of the Glass/Ceramic Sealant Used in SOFCsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2010Wenning N. Liu High operating temperatures of solid oxide fuel cells (SOFCs) require that the sealant must function at a high temperature between 600°C and 900°C and in the oxidizing and reducing environments of fuel and air. This paper describes tests to investigate the temporal evolution of the volume fraction of ceramic phases, the evolution of micro-damage, and the self-healing behavior of the glass,ceramic sealant used in SOFCs. It was found that after the initial sintering process, further crystallization of the glass,ceramic sealant does not stop, but slows down and reduces the residual glass content while boosting the ceramic crystalline content. Under a long-term operating environment, distinct fibrous and needle-like crystals in the amorphous phase disappeared, and smeared/diffused phase boundaries between the glass phase and ceramic phase were observed. Meanwhile, the micro-damage was induced by the cooling down process from the operating temperature to room temperature, which can potentially degrade the mechanical properties of the glass/ceramic sealant. The glass/ceramic sealant exhibited self-healing upon reheating to the SOFC operating temperature, which can restore the mechanical performance of the glass/ceramic sealant. [source] Improvements on the computation of boundaries in QFTINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 12 2006José Carlos Moreno Abstract Quantitative feedback theory (QFT) is an engineering design technique of uncertain feedback systems that uses frequency domain specifications. A key step in QFT is the mapping of these specifications into regions of the Nichols plane, whose borders are usually referred to as boundaries. Boundaries computation is a key design step, thus a precise and efficient computation is critical for both obtaining low bandwidth feedback compensators and simplification of the design process. In this work, the problem of boundaries computation is analysed, introducing a new algorithm based on the computation of level curves of a three-dimensional surface. Besides magnitude boundaries, associated with some specification over the magnitude of a closed-loop transfer function, phase boundaries are also considered. In addition, comparison with previous published algorithms is done in terms of precision and computational efficiency. Copyright © 2006 John Wiley & Sons, Ltd. [source] Hydrate phase equilibria of a near critical fluid: Effect of inhibition and separationAICHE JOURNAL, Issue 7 2001Kasper K. Østergaard The hydrate phase boundary of a near critical fluid (NCF) was measured at 275,289 K in the presence of distilled water, synthetic formation water, and synthetic formation water with 10.41 wt. % methanol. The results agreed well with the predictions of an in-house model, based on a cubic equation of state and statistical thermodynamics. To simulate a typical oil/gas production scenario, the NCF was flashed at 298.1 K and 17.189 MPa, and the resulting liquid was subsequently flashed at 298.0 K and 4.089 MPa. Hydrate free zones of the resulting liquid fractions were measured to investigate the physical separation effect on the hydrate phase boundary. The in-house thermodynamic model was used to simulate the separators conditions and to predict the hydrate free zone of the resulting liquid and the vapor fractions. The predictions agreed closely with the experimental data, demonstrating reliability of the thermodynamic model. The results also showed that the hydrate phase boundaries of the vapor and liquid phases, which resulted from physical separation, are similar to that of the NCF. [source] Bilayer to micelle transition of DMPC and alcohol ethoxylate surfactants as studied by isoperibol calorimetryJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2005Leticia Barriocanal Abstract The interaction of dimyristoylphosphatidylcholine (DMPC) with non-ionic surfactants has been studied using isoperibol calorimetry. Phospholipid-surfactant systems were formed in the isoperibol calorimeter with varying amounts of surfactant and the change in enthalpy on formation was measured. Solubilization of the phospholipid lamellae was assessed as a decrease in the enthalpy of reaction of co-films containing DMPC and increasing amounts of three linear alcohol ethoxylate surfactants: C10H21(OCH2CH2)3OH, C10H21(OCH2CH2)5OH, or C12H25(OCH2CH2)7OH. The isoperibol calorimetry data for DMPC/surfactant/water systems were consistent with a theoretical three-stage model for the solubilization of phospholipids by surfactants, whereby phospholipid bilayers are transformed into mixed micelles with increasing amounts of surfactant. The results indicate that: (i) the interaction between phospholipid and surfactants results in a non-linear correlation between the enthalpy of reaction and the surfactant concentration; (ii) the structural stage of the lamellar to micelle transition (mixed bilayers, mixed micelles, or both) can be determined from calorimetric data; (iii) phase boundaries in the solubilization process (bilayer saturation, micelle saturation) can be identified as break points in the enthalpy-concentration curve; and (iv) increasing the hydrophilicity of the surfactant results in a decrease of the surfactant concentration producing the onset of solubilization. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:1747,1755, 2005 [source] Binary Phase Diagram of the Manganese Oxide,Iron Oxide SystemJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2009Jarrod V. Crum The phase equilibrium of the MnOx,FeOy binary system was measured within a temperature range of 750°,1590°C in air to examine inconsistencies found in literature, i.e., discrepancies related to the boundary between the spinel and hausmannite+spinel phase fields. Several studies are available in the literature that describe this boundary however the results and methods by which they were studied vary namely in terms of the atmosphere (air versus reducing) used and heat treatment/analysis methods. In addition, samples in the discrepancy region of the diagram revert to the hausmannite phase spontaneously upon cooling due to a displacive transformation. In order to accurately measure the phase boundaries, the following measurement methods were used: isothermal heat treatments followed by rapid quenching (in air or water), dilatometry, differential thermal analysis with thermogravimetric analysis, as well as room temperature and hot-stage X-ray diffraction (XRD). Phase assemblage(s) in each specimen were determined by XRD. Data were compared with literature and a new, self consistent phase diagram was developed. The results are reported along with background information and a comparison with previously reported data. This study will support development of a model for thermodynamic equilibria in complex, multioxide silicate melts. [source] Modified Phase Diagram for the Barium Oxide,Titanium Dioxide System for the Ferroelectric Barium TitanateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2007Soonil Lee The ferroelectric phase transition behavior in BaTiO3 was investigated for various annealing times, temperatures, and Ba/Ti ratios by means of a differential scanning calorimeter. Coupling these observations with powder X-ray diffraction and transmission electron microscopy allowed new insights into the barium oxide (BaO),titanium dioxide (TiO2) phase diagram. The transition temperature was varied systematically with the Ba/Ti ratio at annealing temperatures from 1200° to 1400°C in air. The transition temperature decreased with increasing concentrations of BaO and TiO2 partial Schottky defects, and showed a discontinuous change at the phase boundaries. Beyond the solubility region, two peritectoid reactions were confirmed and revised; first around 1150°C for Ba1.054Ti0.946O2.946,Ba2TiO4+BaTiO3 and second 1250°C for BaTi2O5,Ba6Ti17O40+BaTiO3, respectively. All other regimes of the BaO,TiO2 were found to be consistent with the reported diagrams in the literature. [source] An autonomous phase-boundary detection technique for colloidal hard sphere suspension experiments,MICROSCOPY RESEARCH AND TECHNIQUE, Issue 4 2006Mark McDowell Abstract Colloidal suspensions of monodisperse spheres are used as physical models of thermodynamic phase transitions and as precursors to photonic band gap materials. Current techniques for identifying the phase boundaries involve manually identifying the phase transitions, which is very tedious and time-consuming. In addition, current image analysis techniques are not able to distinguish between densely packed phases within conventional microscope images, which are mainly characterized by degrees of randomness or order with similar grayscale value properties. We have developed an intelligent machine vision technique that automatically identifies colloidal phase boundaries. The technique utilizes intelligent image processing algorithms that accurately identify and track phase changes vertically or horizontally for a sequence of colloidal hard sphere suspension images. This technique is readily adaptable to any imaging application wherein regions of interest are distinguished from the background by differing patterns of motion over time. Microsc. Res. Tech. 69:236,245, 2006. Published 2006 Wiley-Liss, Inc. [source] Production of leather-like composites using short leather fibers.POLYMER COMPOSITES, Issue 6 2002Leather-like composites were prepared by addition of chemically modified short leather fibers (SLF) into a plasticized polyvinyl chloride (pPVC) matrix. The fibers were subjected to chemical modification by emulsion polymerization to achieve good interfacial adhesion between SLF and the pPVC matrix. The SLF with chemical modification were obtained from three different reaction conditions where these SLF have different percentages of grafted and deposited PMMA polymer onto the fiber surface. The incorporation of the SLF into the thermoplastic matrix was carried out using a torque-rheometer and the composites obtained were molded by compression. Tensile and tear mechanical tests were performed on composite samples, and the morphology of the fractured surfaces was analyzed using scanning electron microscopy (SEM). The results show that the incorporation by grafting of polymethyl metacrylate (PMMA) onto the fibers produced a significant improvement of their interfacial adhesion to pPVC, promoting the compatibilization between the fiber surface and matrix. The findings are discussed and interpreted in terms of enhanced adhesion at phase boundaries. Overall, the results confirm that it is possible to produce modified leather composites based on a pPVC matrix, which exhibit relatively high tensile strength, tear resistance and flexibility. These composites are very suitable candidate materials for applications in the footwear industry. [source] Rheological behavior of brominated isobutylene-co-paramethylstyrene: Effect of fillers, oil and blending with EPDMPOLYMER ENGINEERING & SCIENCE, Issue 12 2002Bhuwneesh Kumar The melt flow properties of unfilled and filled brominated isobutylene-co-paramethylstyrene (BIMS) were measured by means of a capillary viscometer at three different temperatures (90°C, 110°C and 130°C) and four different shear rates (61, 122, 245 and 306 s,1). The effect of addition of EPDM rubber on melt flow properties of unfilled BIMS was also studied. Evaluation of the processability was done by measuring the extrudate roughness (ER) of the extrudates obtained from the MPT. The viscosity of the systems decreased with the shear rate, indicating their pseudoplastic or shear thinning nature. As expected, the viscosity of BIMS increased with the addition of fillers and decreased with the addition of oil. For the neat systems, viscosity increased with the addition of EPDM, and the blends showed a positive deviation, indicating interdiffusion of the polymer chains across the phase boundaries. The activation energy of the filled systems at constant filler loading increased with increasing filler surface area (N330 > N550 > N774, each at 30 phr loading), and filler loading (50 > 30 > 10 phr, for N330) and decreased with the addition of oil (2.5 > 5.0 > 7.5 phr, for system containing 30 phr of N330). The silica filled system showed a higher activation energy and ER than the carbon black-filled systems. With addition of N330 and N550 carbon blacks to BIMS, the extrudate roughness (ER) decreased, whereas it increased with the addition of N774 carbon black. With an increase in filler loading, ER initially increased and then decreased as compared to the neat system. For the filled systems, ER initially decreased up to 5 phr of oil, beyond which it increased. [source] Flux growth of La-doped lead zirconate stannate titanate antiferroelectric crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2008Lin Wang Abstract Relaxor antiferroelectric single crystals lead lanthanum zirconate stannate titanate (PLZST) with the composition around the morphotropic phase boundary (MPB) have been grown by flux method using 50 wt% PbO-PbF2 -B2O3 as a flux. The obtained crystals are light yellow in color. The XRD patterns revealed that the habitual faces of the obtained crystal are (001). The crystal morphology was studied and related to a layer growth mechanism controlled by two-dimensional growth. The chemical composition of as-grown crystal was analyzed by inductively coupled plasma atomic emission spectrometry (ICP), indicating a slight decrease of the amount of Ti compared to the starting materials. The result was verified by the XRD patterns with the phase transformation from the co-existence of tetragonal and rhombohedra phases to the single tetragonal phase. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Phase transitions and heat conduction in post-glacial reboundGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2002M. E. Tamisiea Summary We have developed a method for including phase boundary conditions into post-glacial rebound models that allows for conduction of latent heat away from the boundary. This method returns the chemical boundary results if latent heat conducts away from the phase boundary too slowly to allow the transition to proceed, as is commonly argued. This is not necessarily the case, however. For example, the secular change of the geoid and the vertical uplift rates for phase boundaries with latent heat conduction can differ from the chemical boundary results by up to 10 and 15 per cent, respectively. When modelling the phase transition, we consider two scenarios: the latent heat is released either at a narrow boundary that separates the two phases or over a thick mixed region of the two phases. In the case where the phase transition occurs over a thick enough region (5,10 km), the final results are close to the results obtained by considering a phase boundary that ignores the release of latent heat completely. This thick boundary formulation also suggest that the phase boundaries could respond nearly instantaneously, changing both the elastic load and body Love numbers. However, we have not considered kinetics, the energetics of the mechanisms of the phase transitions, in this formulation. This work suggests a greater knowledge of the kinetics near equilibrium phase transitions is required. A naive calculation indicates that the kinetics will not be a significant factor for post-glacial rebound but will be a limiting factor for earth tides. [source] Hydrate phase equilibria of a near critical fluid: Effect of inhibition and separationAICHE JOURNAL, Issue 7 2001Kasper K. Østergaard The hydrate phase boundary of a near critical fluid (NCF) was measured at 275,289 K in the presence of distilled water, synthetic formation water, and synthetic formation water with 10.41 wt. % methanol. The results agreed well with the predictions of an in-house model, based on a cubic equation of state and statistical thermodynamics. To simulate a typical oil/gas production scenario, the NCF was flashed at 298.1 K and 17.189 MPa, and the resulting liquid was subsequently flashed at 298.0 K and 4.089 MPa. Hydrate free zones of the resulting liquid fractions were measured to investigate the physical separation effect on the hydrate phase boundary. The in-house thermodynamic model was used to simulate the separators conditions and to predict the hydrate free zone of the resulting liquid and the vapor fractions. The predictions agreed closely with the experimental data, demonstrating reliability of the thermodynamic model. The results also showed that the hydrate phase boundaries of the vapor and liquid phases, which resulted from physical separation, are similar to that of the NCF. [source] Two-phase flow electrosynthesis: Comparing N -octyl-2-pyrrolidone,aqueous and acetonitrile,aqueous three-phase boundary reactionsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 1 2009Stuart M. MacDonald Abstract A microfluidic double channel device is employed to study reactions at flowing liquid,liquid junctions in contact with a boron-doped diamond (BDD) working electrode. The rectangular flow cell is calibrated for both single-phase liquid flow and biphasic liquid,liquid flow for the case of (i) the immiscible N -octyl-2-pyrrolidone (NOP),aqueous electrolyte system and (ii) the immiscible acetonitrile,aqueous electrolyte system. The influence of flow speed and liquid viscosity on the position of the phase boundary and mass transport-controlled limiting currents are examined. In contrast to the NOP,aqueous electrolyte case, the acetonitrile,aqueous electrolyte system is shown to behave close to ideal without ,undercutting' of the organic phase under the aqueous phase. The limiting current for three-phase boundary reactions is only weakly dependent on flow rate but directly proportional to the concentration and the diffusion coefficient in the organic phase. Acetonitrile as a commonly employed synthetic solvent is shown here to allow effective three-phase boundary processes to occur due to a lower viscosity enabling faster diffusion. N -butylferrocene is shown to be oxidised at the acetonitrile,aqueous electrolyte interface about 12 times faster when compared with the same process at the NOP,aqueous electrolyte interface. Conditions suitable for clean two-phase electrosynthetic processes without intentionally added supporting electrolyte in the organic phase are proposed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Transition from microemulsion to emulsion polymerization: Mechanism and final propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2004Kevin D. Hermanson Abstract Microemulsion and emulsion polymerization can have some similarities in starting conditions and polymerization mechanisms, but the resulting latices are unalike in particle size and molecular weight. Here we show that polymerizations can be formulated that display the characteristics often separately associated with microemulsion or emulsion polymerization. Kinetic modeling and particle size measurements show that emulsion polymerizations with initial concentrations close to the microemulsion,emulsion phase boundary demonstrate relatively fast consumption of monomer droplets and produce smaller particles. Because of their high surfactant concentrations, none of the emulsion polymerizations examined demonstrate the classical Smith,Ewart kinetics usually associated with emulsion polymerization. Instead these emulsion polymerizations have a long period of particle nucleation that subsides only after the disappearance of monomer droplets. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5253,5261, 2004 [source] Phase Characteristics and Piezoelectric Properties in the Bi0.5Na0.5TiO3,BaTiO3,K0.5Na0.5NbO3 SystemJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2010Shan-Tao Zhang Lead-free 0.94Bi0.5Na0.5TiO3,(0.06,x)BaTiO3,xK0.5Na0.5NbO3 (x=0,0.06) ceramics were prepared. All these compositions have a structure close to the rhombohedral,tetragonal morphotropic phase boundary (MPB) and good electric properties at room temperature. No significant composition dependence of ferroelectric property can be established, whereas a dependence of piezoelectric properties can be observed, e.g. the piezoelectric coefficient (d33), planar coupling factor (kp), and field-induced strain (S) increase with increasing x when x,0.01 and then tend to decrease. The highest d33, kp, and bipolar strain are 118 pC/N, 0.29, and 0.32%, respectively, in the composition with x=0.01. The results not only indicate that BNT,BT,KNN lead-free piezoceramics can persist in the structure close to MPB in a wide composition range but that they may also be helpful for further investigation on lead-free piezoceramics. [source] Subcoercive Cyclic Electrical Loading of Lead Zirconate Titanate Ceramics II: Time-Resolved X-Ray DiffractionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2009Abhijit Pramanick Structural changes such as non-180° domain wall motion and lattice strains in Pb(Zr,Ti)O3 ceramics are measured during the application of subcoercive cyclic electric fields using time-resolved high-energy X-ray diffraction with a stroboscopic data collection technique. The contributions to the electric-field-induced strains from non-180° domain wall motion and lattice distortions are determined as a function of material composition and type of dopant. For the different compositions studied, the largest strains due to non-180° domain wall motion are measured for La-doped tetragonal ceramics with a composition close to the morphotropic phase boundary. It is further observed that strain contributions from both non-180° domain wall motion and lattice distortions can be nonlinear with respect to the applied electric field. The correlation between the electric-field-induced structural changes and the macroscopic piezoelectric properties is discussed. [source] Enhancing Electrical Properties in NBT,KBT Lead-Free Piezoelectric Ceramics by Optimizing Sintering TemperatureJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008Ya-Ru Zhang Conventional sintering of (Na1,xKx)0.5Bi0.5TiO3 (abbreviated as NKBTx, x=18,22 mol%) lead-free piezoelectric ceramics was investigated to clarify the optimal sintering temperature for densification and electrical properties. Both sintered density and electrical properties were sensitive to sintering temperature; particularly, the piezoelectric properties deteriorated when the ceramics were sintered above the optimum temperature. The NKBT20 and NKBT22 ceramics synthesized at 1110°,1170°C showed a phase transition from tetragonal to rhombohedral symmetry, which was similar to the morphotropic phase boundary (MPB). Because of such MPB-like behavior, the highest piezoelectric constant (d33) of about 192 pC/N with a high electromechanical coupling factor (kp) of about 32% were obtained in the NKBT22 ceramics sintered at 1150°C. [source] Peculiarities of Pyroelectric Resonance,Antiresonance Phenomena in PZT CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008Svetlana Bravina The pyroelectric characteristics of lead,zirconate,titanate (PZT) ceramics of composition near the morphotropic phase boundary were studied by the photothermomodulation method. The frequency spectra of the amplitude and phase of pyroelectric response in the current and voltage modes were transformed into thermowave profiles. The asymmetry of thickness profiles of the pyroactivity distribution and its reversal under reversing poling voltage polarity were revealed. Attention has been concentrated on elucidation of the peculiarities of pyroelectric resonance,antiresonance (PyRAR) and inverse antiresonance,resonance (PyARR) sequences observed in the 25,35 kHz range thermowave excitation of flexural mode thermomechanical vibrations induced by periodical thermal stresses in the undersurface layer of PZT disks. External voltage-controllable reversible inversion of the sequence PyRAR to PyARR under IR-beam probing of the opposite disk sides, being at different polarities of poling voltage, was found. The connection between poling voltage polarity, the shape of the thermowave profile of pyroelectric parameters, and the inversion of Py (RAR,ARR) sequence were ascertained. The results are compared with those observed earlier for edge-fixed PVDF and P(VDF/TrFE) copolymer films and discussed in regard to highly sensitive pyroelectric detectors. [source] Properties of Compositionally Graded BiScO3,PbTiO3 Thin Films Fabricated by a Sol,Gel ProcessJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2007Hai Wen The compositionally graded BiScO3,PbTiO3 (BSPT) thin films were fabricated on Pt/Ti/SiO2/Si by a sol,gel method. For the up-graded thin film, the PbTiO3 content increased from the film,substrate interface to the surface of the film, while the down-grade thin film showed the opposite trend. The graded thin films exhibited single-phase structures and dense microstructures. The dielectric and ferroelectric properties of the thin films were investigated. The results showed that the compositionally graded BSPT thin films had similar remanent polarization value but a higher dielectric constant, dielectric tunability, and piezoelectric coefficient d33 compared with the homogeneous thin film with a composition of 0.36BiScO3,0.64PbTiO3 at the morphotropic phase boundary. [source] High-Energy Density Ceramic Composition in the System Pb(Zr,Ti)O3,Pb[(Zn,Ni)1/3Nb2/3]O3JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2006Rashed Adnan Islam This study reports a high-energy density piezoelectric polycrystalline ceramic composition in the system Pb(Zr1,xTix)O3,Pb[(Zn1,yNiy)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|=,n, where , 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. [source] Thermal Stability of (1,x)BiScO3,xPbTiO3 Piezoelectric Ceramics for High-Temperature Sensor ApplicationsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2006Si Chen High-temperature piezoelectric (1,x)BiScO3,xPbTiO3 ceramics with composition (x=0.62, 0.63, 0.64, and 0.65) near the morphotropic phase boundary were fabricated. A thermal depoling experiment was used to investigate the stability of polarization at the temperature range from 200° to 460°C. The results indicated that samples with rhombohedral phase began to depole when the temperature was higher than 300°C, while samples with a tetragonal phase showed good resistance to thermal depoling up to 440°C, close to their Curie temperature. [source] Compositional Dependence of Piezoelectric Properties in NaxK1,xNbO3 Lead-Free Ceramics Prepared by Spark Plasma SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2006Bo-Ping Zhang Lead-free piezoelectric NaxK1,xNbO3 (x=20,80 mol%) ceramics were fabricated using spark plasma sintering at a low temperature (920°C). All the NaxK1,xNbO3 ceramics showed a similar orthorhombic phase structure, while the corresponding lattice parameters decreased from the KNbO3 side to the NaNbO3 side with increasing Na content. A discontinuous change in lattice parameter close to composition of 60 mol% Na indicated the presence of a transitional area that is similar to the morphotropic phase boundary (MPB) in NaxK1,xNbO3 ceramics. The sintered density of the NaxK1,xNbO3 ceramics decreased with increasing Na content, from a relative density of 99% for the K-rich side to 92% for the Na-rich side. The piezoelectric constant d33 and planar mode electromechanical coupling coefficient kp showed a maximum value of 148 pC/N and 38.9%, respectively, due to the similar MPB effects in the PZT system. [source] Control of Crystal Orientation and Piezoelectric Response of Lead Zirconate Titanate Thin Films Near the Morphotropic Phase BoundaryJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2002Ken-ichi Kakimoto PbZr0.53Ti0.47O3 (PZT) thin films with various preferred crystallographic orientations were synthesized on various substrates using pulsed laser deposition techniques. Larger piezoelectric displacement, which involved the bending vibration of the PZT film/substrate, was observed in randomly oriented PZT thin film than that in (100)- and (111)-preferred texture films. This result was discussed by correlation with the number of effective spontaneous polarization axes in the morphotropic phase boundary of the PZT system. Moreover, polarization fatigue was found to lower the electric-field-induced displacement significantly, indicating a large contribution of ferroelectric domain motion to the piezoelectric response of PZT thin films under bipolar drive. [source] Phase Stability and Ferroelectric Properties of Lead Strontium Zirconate Titanate CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2001Yongjian Yu The effect of compositional modifications on the field-induced phase-transition behavior and dielectric properties of strontium-doped lead zirconate titanate (PZT) ceramics was studied. PZT compositions with different strontium and titanium contents, within the general formula Pb1,xSrx(Zr1,yTiy)O3 and located in the tetragonal antiferroelectric (AFE) and rhombohedral ferroelectric (FE) phase fields were prepared by tape casting and sintering. X-ray diffraction and polarization measurements were used to locate compositions suitable for investigation of the field-induced AFE,FE phase transition. The results indicated that a higher Sr2+ content decreased the polarization and hysteresis and increased the switching field; a lower Ti4+ content decreased the polarization and increased the switching field and hysteresis. A high room-temperature dielectric constant was obtained for compositions near the phase boundary. These results suggest that a combination of both A -site and B -site modifications can be used to tailor ferroelectric properties, such as the switching field and hysteresis, of these strontium-doped PZTs displaying a field-induced AFE,FE phase transition. [source] | ||||||||||||||||||||||||||||||||||