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Ferroelectric
Kinds of Ferroelectric Terms modified by Ferroelectric Selected AbstractsFully Transparent Non-volatile Memory Thin-Film Transistors Using an Organic Ferroelectric and Oxide Semiconductor Below 200,°CADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Sung-Min Yoon Abstract A fully transparent non-volatile memory thin-film transistor (T-MTFT) is demonstrated. The gate stack is composed of organic ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] and oxide semiconducting Al-Zn-Sn-O (AZTO) layers, in which thin Al2O3 is introduced between two layers. All the fabrication processes are performed below 200,°C on the glass substrate. The transmittance of the fabricated device was more than 90% at the wavelength of 550,nm. The memory window obtained in the T-MTFT was 7.5,V with a gate voltage sweep of ,10 to 10,V, and it was still 1.8,V even with a lower voltage sweep of ,6 to 6,V. The field-effect mobility, subthreshold swing, on/off ratio, and gate leakage currents were obtained to be 32.2,cm2 V,1 s,1, 0.45,V decade,1, 108, and 10,13 A, respectively. All these characteristics correspond to the best performances among all types of non-volatile memory transistors reported so far, although the programming speed and retention time should be more improved. [source] Tunable Injection Barrier in Organic Resistive Switches Based on Phase-Separated Ferroelectric,Semiconductor Blends,ADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Kamal Asadi Abstract Organic non-volatile resistive bistable diodes based on phase-separated blends of ferroelectric and semiconducting polymers are fabricated. The polarization field of the ferroelectric modulates the injection barrier at the semiconductor,electrode contact and, hence, the resistance of the comprising diodes. Comparison between the on- and off-current of the switching diodes, with the current measured for semiconductor-only diodes reveals that the switching occurs between bulk-limited, i.e., space-charge-limited, and injection-limited current transport. By deliberately varying the HOMO energy of the semiconductor and the work-function of the metal electrode, it is demonstrated that injection barriers up to 1.6,eV can be surmounted by the ferroelectric polarization yielding on/off current modulations of more than five orders of magnitude. The exponential dependence of the current modulation with a slope of 0.25,eV/decade is rationalized by the magnitude of the injection barrier. [source] The Inlaid Al2O3 Tunnel Switch for Ultrathin Ferroelectric FilmsADVANCED MATERIALS, Issue 28 2009An Quan Jiang Ferroelectric switching in ultrathin Al2O3/PZT bilayers is studied and used to modulate the applied electric field, allowing the development of novel applications of the combined dielectric tunnel switch/ferroelectric functional layer that can assist in the development of completely new types of electronic, electromechanical, and electrochemical devices. [source] Effects of Rare-Earth Dopants on the Ferroelectric and Pyroelectric Properties of Strontium Barium Niobate CeramicsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2009Yingbang Yao Effects of various rare-earth (RE) dopants (Y3+, La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tm3+, Dy3+, Er3+, and Yb3+) on the dielectric, ferroelectric, and pyroelectric properties of Sr0.5Ba0.5Nb2O6 (SBN50) ceramics were investigated. In the present studies, the doping concentrations of all the RE dopants were fixed at 1 mol%. Their potential usefulness in pyroelectric applications was discussed based on their measured pyroelectric detectivity figure of merit (FOM). On the basis of our studies, for RE dopants with atomic numbers smaller than Nd, their dielectric constants were greatly increased, while for RE dopants with atomic numbers larger than Sm, their dielectric constants as well as dielectric losses became smaller. Among various dopants, Eu-doped SBN showed the most improved ferroelectric properties. Its remnant polarization (Pr) was increased to 4.86 ,C/cm2 as compared with 3.23 ,C/cm2 obtained in undoped SBN50. On the other hand, Gd-doped SBN exhibited the largest pyroelectric coefficient of 168 ,C/m2 K, which was over three times of that of the undoped sample (49 ,C/m2 K). The work shows that Gd-doped SBN exhibits the greatest potential for pyro-applications because it bears the largest FOM of 0.45 × 10,5 Pa,0.5 [Correction: After online publication on 11/05/2008, an error was found in this article. The original value, 1.35×10,5 Pa,0.5, was incorrect. The data has been replaced with the correct value.]. [source] Ferroelectric, Electroactive, and Dielectric-Relaxation Behavior of FluoropolymersADVANCED MATERIALS, Issue 12 2004C. Ang The discovery of piezoelectricity in poly(vinylidene fluoride) polymers and related co- and terpolymers has led to much interest in the physics of these materials because of their great potential for many actuator applications. The electroactive strain, ferroelectric polarization, and dielectric behavior of an irradiated poly(vinylidene fluoride,trifluoroethylene) (P(VDF,TrFE)) copolymer and non-irradiated poly(vinylidene fluoride,trifluoroethylene,chlorotrifluoroethylene) (P(VDF,TrFE,CTFE)) terpolymer are reported here, with special attention given to the analysis of the complex permittivity. [source] Ferroelectric and Piezoelectric Properties of Na1,xBaxNb1,xTixO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2006J. T. Zeng Piezoelectric ceramics Na1,xBaxNb1,xTixO3 with low BaTiO3 concentrations x have been prepared by the solid-state reaction method, and their ferroelectric and piezoelectric properties have been studied. The ceramics are classic ferroelectrics when x,0.10, and the ferroelectric,paraelectric phase transition becomes diffusive when x,0.15. A low doping level of BaTiO3 changes the NaNbO3 ceramics from antiferroelectric to ferroelectric. With the increase in BaTiO3 doping level, the Curie temperature of ceramics decreases linearly and the remnant polarization and coercive field also decrease, while their dielectric constant increases. Na0.9Ba0.1Nb0.9Ti0.1O3 ceramics show the largest piezoelectric constant d33 (147 pC/N) and good sinterability, suggesting that it is a good candidate for lead-free piezoelectric ceramics. [source] Ferroelectric, piezoelectric, pyroelectric and Raman spectroscopy studies on BaTi0.9(Fe1/2Nb1/2)0.1O3 ceramicPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2008Z. Abdelkafi Abstract The hysteresis, piezoelectric and pyroelectric properties were measured in the temperature range near the ferroelectric,paraelectric phase transition. The BaTi0.9(Fe1/2Nb1/2)0.1O3 ceramic exhibits typical ferroelectric P ,E hysteresis behavior with a remanant polarization, Pr, of about 7.52 ,C/cm2 detected at 155 K. The electromechanical properties of this composition were measured using the resonance method. The ceramic provides high piezoelectric performance at the temperature of transition (Tmax = 216 K): the piezoelectric constant is d31 = 140 pC/N and the electromechanical coupling factor was kP = 22%. The pyroelectric study confirms the dielectric and ferroelectric measurements. The pyroelectric coefficient is about 125 nC/cm2 K at Tmax. Raman spectra of BaTi0.9(Fe1/2Nb1/2)0.1O3 ceramic were taken at various temperatures and measured over the wave number range from 150 to 1300 cm,1. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] ChemInform Abstract: AgCrS2: A Spin Driven Ferroelectric.CHEMINFORM, Issue 4 2010K. Singh Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: (NH4)2Te2WO8: A New Polar Oxide with Second-Harmonic Generating, Ferroelectric, and Pyroelectric Properties.CHEMINFORM, Issue 5 2008Jun-Ho Kim Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Effect of NaCl filler on ferroelectric phase and polaron configurations of PVDF filmsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2007I. S. ElashmawiArticle first published online: 8 MAR 200 Abstract Polyvinyldene fluoride (PVDF) films filled with NaCl of mass fraction range 1 , W , 6 % were prepared by casting technique. Their crystalline structure, thermal, optical properties and Electron spin resonance (ESR) were examined. X-ray diffraction (XRD) and differential thermal analysis (DTA) measurements indicated a maximum ferroelectric ,-phase increment at 4%. DTA was used to identify the phase transition temperatures, the order of reaction and the activation energy of melting. The UV-Visible optical absorption implied a minimum value of the estimated optical energy gap at W = 4%. ESR spectra contained a Lorentizian signal exhibiting a minimum value of the symmetry factor at W = 4%. The energy levels of the optical gap boundaries were though to contribute to ESR transitions. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Chemical Bonding Assembly of Multifunctional Oxide NanocompositesADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Gary Evans Abstract The synthesis, functionalization and assembly of metal oxide nanoparticles BaTiO3 and CoFe2O4 is presented. The ferroelectric (BaTiO3) and ferromagnetic (CoFe2O4) oxide nanoparticle surfaces are directly functionalized via the anchoring of phosphonic acid and aminosilane molecules that engender the nanoparticles with terminal carboxylic acid and amine functional groups, respectively. These promote the electrostatic self-assembly of the particles in non-polar solvents and permit the synthesis of more chemically robust assemblies linked by the covalent amide bond via the addition of the chemical coupling agent N - N, -dicyclohexylcarbodiimide. This functionalization and assembly procedure is applied to two systems: the first comprised of 50,nm BaTiO3 and 10,nm CoFe2O4 particles and the second of 200,nm BaTiO3 and 12.5,nm CoFe2O4 particles. The latter composites possess magnetoelectric properties when processed into dense ceramics and, as a direct result of the assembly performed in solution, have a high degree of homogeneity between the ferroelectric and ferromagnetic phases. The developed functionalization and assembly procedure is considered to be adaptable to the preparation of other hybrid oxide nanomaterials with different property combinations. [source] Tunable Injection Barrier in Organic Resistive Switches Based on Phase-Separated Ferroelectric,Semiconductor Blends,ADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Kamal Asadi Abstract Organic non-volatile resistive bistable diodes based on phase-separated blends of ferroelectric and semiconducting polymers are fabricated. The polarization field of the ferroelectric modulates the injection barrier at the semiconductor,electrode contact and, hence, the resistance of the comprising diodes. Comparison between the on- and off-current of the switching diodes, with the current measured for semiconductor-only diodes reveals that the switching occurs between bulk-limited, i.e., space-charge-limited, and injection-limited current transport. By deliberately varying the HOMO energy of the semiconductor and the work-function of the metal electrode, it is demonstrated that injection barriers up to 1.6,eV can be surmounted by the ferroelectric polarization yielding on/off current modulations of more than five orders of magnitude. The exponential dependence of the current modulation with a slope of 0.25,eV/decade is rationalized by the magnitude of the injection barrier. [source] Unraveling Deterministic Mesoscopic Polarization Switching Mechanisms: Spatially Resolved Studies of a Tilt Grain Boundary in Bismuth FerriteADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Brian J. Rodriguez Abstract The deterministic mesoscopic mechanism of ferroelectric domain nucleation is probed at a single atomically-defined model defect: an artificially fabricated bicrystal grain boundary (GB) in an epitaxial bismuth ferrite film. Switching spectroscopy piezoresponse force microscopy (SS-PFM) is used to map the variation of local hysteresis loops at the GB and in its immediate vicinity. It is found that the the influence of the GB on nucleation results in a slight shift of the negative nucleation bias to larger voltages. The mesoscopic mechanisms of domain nucleation in the bulk and at the GB are studied in detail using phase-field modeling, elucidating the complex mechanisms governed by the interplay between ferroelectric and ferroelastic wall energies, depolarization fields, and interface charge. The combination of phase-field modeling and SS-PFM allows quantitative analysis of the mesoscopic mechanisms for polarization switching, and hence suggests a route for unraveling the mechanisms of polarization switching at a single defect level and ultimately optimizing materials properties through microstructure engineering. [source] Functional Perovskites , From Epitaxial Films to Nanostructured Arrays,ADVANCED FUNCTIONAL MATERIALS, Issue 24 2008Ionela Vrejoiu Abstract Functional perovskite materials gain increasing significance due to their wide spectrum of attractive properties, including ferroelectric, ferromagnetic, conducting and multiferroic properties. Due to the developments of recent years, materials of this type can conveniently be grown, mainly by pulsed laser deposition, in the form of epitaxial films, multilayers, superlattices, and well-ordered arrays of nanoislands. These structures allow for investigations of preparation,microstructure,property relations. A wide variation of the properties is possible, determined by strain, composition, defect contents, dimensional effects, and crystallographic orientation. An overview of our corresponding work of recent years is given, particularly focusing on epitaxial films, superlattices and nanoisland arrays of (anti)ferroelectric and multiferroic functional perovskites. [source] Multiple NaNbO3/Nb2O5 Heterostructure Nanotubes: A New Class of Ferroelectric/Semiconductor NanomaterialsADVANCED MATERIALS, Issue 15 2010Chenglin Yan Multiple NaNbO3 nanoplates are created within Nb2O5 nanotubes forming a unique class of heterostructure nanotubes combining ferroelectric and semiconducting nanomaterials. Local piezoelectric studies on NaNbO3 nanoplates show clear ferroelectric behavior (see figure), while the semiconductive properties of the host Nb2O5 nanotubes allows for switching of electrical conductivity by an external electric field. [source] High-Strain Lead-free Antiferroelectric ElectrostrictorsADVANCED MATERIALS, Issue 46 2009Shan-Tao Zhang Research on lead-free piezoceramics has dramatically increased over the last years due to stringent legislation demanding to phase out current lead-containing piezoceramics. The use of electrostrictive materials for electric-field induced strain has been largely overlooked. In this paper we demonstrate that electrostrictive materials around a ferroelectric,antiferroelectric transition are capable of providing high strains over a wide temperature regime that was not accessible before. [source] Ferroelectric Switching in Multiferroic Magnetite (Fe3O4) Thin FilmsADVANCED MATERIALS, Issue 44 2009Marin Alexe Real-time ferroelectric polarization switching in magnetite epitaxial thin films is reported, proving that magnetite is not only historically the first material showing magnetism and correlated electron properties, but also that it is ferroelectric with a value of the ferroelectric polarization approaching that of well-known ferroelectric materials such as BaTiO3. [source] High-Mobility Nonvolatile Memory Thin-Film Transistors with a Ferroelectric Polymer Interfacing ZnO and Pentacene ChannelsADVANCED MATERIALS, Issue 42 2009Kwang H. Lee Nonvolatile memory ferroelectric thin-film transistors (FeTFT) with P(VDF-TrFE) polymer are demonstrated with both n-channel ZnO and p-channel pentacene. A high mobility of ,1,cm2 V,1 s,1 and large memory window of ,20,V are achieved through the organic ferroelectric, inorganic channel hybrid device of ZnO-FeTFT. WRITE/ERASE states are clearly distinguished by ±20,V switching for ZnO- and pentacene-FeTFTs. [source] Domain Engineering for Enhanced Ferroelectric Properties of Epitaxial (001) BiFeO Thin FilmsADVANCED MATERIALS, Issue 7 2009Ho Won Jang Two-variant stripe domains in BiFeO3 films on miscut (001) SrTiO3 substrates exhibit square-like, complete ferroelectric switching with low leakage current. Both the preferential distortion of BiFeO3 unit cells and the persistent step-flow growth induced by the substrate anisotropy are the origins of the formation of the two-variant stripe domains in (001) BiFeO3 films. [source] Effects of Rare-Earth Dopants on the Ferroelectric and Pyroelectric Properties of Strontium Barium Niobate CeramicsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2009Yingbang Yao Effects of various rare-earth (RE) dopants (Y3+, La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tm3+, Dy3+, Er3+, and Yb3+) on the dielectric, ferroelectric, and pyroelectric properties of Sr0.5Ba0.5Nb2O6 (SBN50) ceramics were investigated. In the present studies, the doping concentrations of all the RE dopants were fixed at 1 mol%. Their potential usefulness in pyroelectric applications was discussed based on their measured pyroelectric detectivity figure of merit (FOM). On the basis of our studies, for RE dopants with atomic numbers smaller than Nd, their dielectric constants were greatly increased, while for RE dopants with atomic numbers larger than Sm, their dielectric constants as well as dielectric losses became smaller. Among various dopants, Eu-doped SBN showed the most improved ferroelectric properties. Its remnant polarization (Pr) was increased to 4.86 ,C/cm2 as compared with 3.23 ,C/cm2 obtained in undoped SBN50. On the other hand, Gd-doped SBN exhibited the largest pyroelectric coefficient of 168 ,C/m2 K, which was over three times of that of the undoped sample (49 ,C/m2 K). The work shows that Gd-doped SBN exhibits the greatest potential for pyro-applications because it bears the largest FOM of 0.45 × 10,5 Pa,0.5 [Correction: After online publication on 11/05/2008, an error was found in this article. The original value, 1.35×10,5 Pa,0.5, was incorrect. The data has been replaced with the correct value.]. [source] Large Electric Polarization and Exchange Bias in Multiferroic BiFeO3,ADVANCED MATERIALS, Issue 11 2006J. Dho Low-leakage BiFeO3 films have been grown with saturated ferroelectric hysteresis loops (see figure) and a very large remanent polarization. The antiferromagnetic nature of BiFeO3 films is confirmed by the appearance of an exchange bias in BiFeO3 -based spin-valve multilayers. The results imply that there is potential for room-temperature applications of BiFeO3 that combine ferroelectric and antiferromagnetic functionality. [source] Micro-Raman study of Zr-substituted Bi4Ti3O12 ceramicsJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2007S. R. Das Abstract We have studied the lattice vibrational modes of Zr-substituted Bi4Ti3O12 ceramics using micro-Raman spectroscopy. Replacement of Zr at the Ti site in the perovskite block is found from the increase in the lattice parameters as a function of Zr contents. Combined X-ray diffraction patterns and Raman analysis suggested less than 40 mole% Zr solubility in Bi4Ti3O12. At 40 mole% of Zr substitution or above, the unreacted monoclinic-phase ZrO2 is observed in the X-ray diffraction patterns and the Raman spectra. The incorporation of Zr in Bi4Ti3O12 reduces the soft mode wavenumber and the transition temperature. Moreover, temperature dependent studies confirmed the ferroelectric to paraelectric transition in Bi4Ti3O12 at about 675 °C. On increasing the Zr content up to 40% on the Ti sites of Bi4Ti3O12, a systematic decrease in the phase transition temperature from 675 to 630 °C was observed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Microstructure and Relaxor Behavior of Dense Fine-Grain FeTiTaO6 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2010Yun Shi A new type of FeTiTaO6 ceramics with a high density was synthesized by the solid-state method. X-ray diffraction and scanning electron microscopy patterns indicate that the specimens exhibit a rutile structure and the mean particle size was about 200,300 nm. The heterovalent substitutions of Fe3+ and Ta5+ at Ti4+ site drive the incipient ferroelectric to the relaxor behavior, and a strong dispersion of the maximum dielectric permittivity appears around Tm, which shifts towards higher temperatures with the increasing frequency. The variation of Tm with frequency follows the Vogel,Fulcher relationship well, wherein Ea=0.068 eV, Tf=508 K, and f0=109 Hz. These results indicate that the nonperovskite-type FeTiTaO6 ceramic is a promising candidate for lead-free relaxor ferroelectrics in practical applications. [source] Hydrothermal Synthesis and Spark Plasma Sintering of (K, Na)NbO3 Lead-Free PiezoceramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Nan Liu A facile hydrothermal route was adopted for synthesis of lead-free piezoceramics (K, Na)NbO3 powders. The influences of temperature and KOH/NaOH concentration on the resultant powders were investigated. Although two similar perovskite phases appeared when K/Na ratio tended toward 1:1, the two-phase coexistence tendency was weakened by increasing hydrothermal reaction temperature, and consequently only one phase could be obtained after spark plasma sintering. Reasonably good ferroelectric and piezoelectric properties were obtained for the samples after postannealing, whose piezoelectric constant (d33) reached 135 pC/N. The optimal remnant polarization (Pr) and mechanical quality factor (Qm) were 26.2 ,C/cm2 and 164, respectively, which were both twice as much as those of the samples using powders prepared from solid-state reaction. [source] High-Temperature Instability of Li- and Ta-Modified (K,Na)NbO3 PiezoceramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2008Yongli Wang This paper addresses the high-temperature instability of Li- and Ta-modified (K,Na)NbO3 piezoceramics. The grains with abnormal size evolve out of the fine matrix grains during high-temperature annealing. They are found to be precipitates with a tetragonal tungsten bronze structure, which result from the volatilization and segregation of the alkali metal elements. With the growth of the abnormal grains the composition of the perovskite matrix phase also changes remarkably, as has been suggested by EDX analysis (for Na) and electric measurements (for Li). These variations lead to a large increase in the tetragonal/orthorhombic phase transition temperature and appreciable variations in the dielectric, ferroelectric, and piezoelectric properties of the ceramic samples. Control of the volatilization of the alkali metal elements can efficiently depress the abnormal grain growth and the compositional segregation. [source] Electrical Properties of Textured Potassium Strontium Niobate (KSr2Nb5O15) Ceramics Fabricated by Reactive Templated Grain GrowthJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2008Sedat Alkoy Highly [001] textured KSr2Nb5O15 (KSN) ceramics were fabricated by templated grain growth using acicular KSN template particles (5,15 wt%) and reactive matrix of SrNb2O6 and KNbO3. Excess Nb2O5 (1,1.5 wt%) was added as a liquid former. Increasing sintering temperature and time resulted in increased texture with a maximum texture fraction of 0.98. Dielectric, ferroelectric, and piezoelectric measurements indicate anisotropic properties that are close to single crystal values in the textured ceramics with the highest Pr,18 ,C/cm2, Ps,25 ,C/cm2, and d33=65 pC/N obtained in the c -axis direction. [source] Inspection of Remanent Polarization in the Ferroelectric Ceramic PZT 95/5 Through Pyroelectric EffectJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2007Fu-Ping Zhang Shock-induced depoling of the ferroelectric (FE) ceramic PZT 95/5 is utilized in a number of pulsed power devices. Nondestructive testing of remanent polarization of PZT 95/5 is developed by pyroelectric effect in this paper. Approximately linear relation between the change of polarization during low- to high-temperature rhombohedral FE phase and the remanent polarization was found through pyroelectricity of a single piece of PZT 95/5 ceramics. The change of polarization of a prototype for shock-driven pulsed power during the FEHT,FELT phase transformation was also investigated through directly measuring the pyroelectric current. Results indicate that pyroelectric effect caused by the reversible FEHT,FELT phase transition could be used as a non-destructive inspection for the remanent polarization of a prototype about shock-driven pulsed power supply. [source] Ferroelectric and Piezoelectric Properties of Na1,xBaxNb1,xTixO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2006J. T. Zeng Piezoelectric ceramics Na1,xBaxNb1,xTixO3 with low BaTiO3 concentrations x have been prepared by the solid-state reaction method, and their ferroelectric and piezoelectric properties have been studied. The ceramics are classic ferroelectrics when x,0.10, and the ferroelectric,paraelectric phase transition becomes diffusive when x,0.15. A low doping level of BaTiO3 changes the NaNbO3 ceramics from antiferroelectric to ferroelectric. With the increase in BaTiO3 doping level, the Curie temperature of ceramics decreases linearly and the remnant polarization and coercive field also decrease, while their dielectric constant increases. Na0.9Ba0.1Nb0.9Ti0.1O3 ceramics show the largest piezoelectric constant d33 (147 pC/N) and good sinterability, suggesting that it is a good candidate for lead-free piezoelectric ceramics. [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] Ferroelectric, piezoelectric, pyroelectric and Raman spectroscopy studies on BaTi0.9(Fe1/2Nb1/2)0.1O3 ceramicPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2008Z. Abdelkafi Abstract The hysteresis, piezoelectric and pyroelectric properties were measured in the temperature range near the ferroelectric,paraelectric phase transition. The BaTi0.9(Fe1/2Nb1/2)0.1O3 ceramic exhibits typical ferroelectric P ,E hysteresis behavior with a remanant polarization, Pr, of about 7.52 ,C/cm2 detected at 155 K. The electromechanical properties of this composition were measured using the resonance method. The ceramic provides high piezoelectric performance at the temperature of transition (Tmax = 216 K): the piezoelectric constant is d31 = 140 pC/N and the electromechanical coupling factor was kP = 22%. The pyroelectric study confirms the dielectric and ferroelectric measurements. The pyroelectric coefficient is about 125 nC/cm2 K at Tmax. Raman spectra of BaTi0.9(Fe1/2Nb1/2)0.1O3 ceramic were taken at various temperatures and measured over the wave number range from 150 to 1300 cm,1. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||||||||||||||