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Ferroelectric Properties (ferroelectric + property)
Selected AbstractsDomain 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] Intrinsic Ferroelectric Properties of Strained Tetragonal PbZr0.2Ti0.8O3 Obtained on Layer,by,Layer Grown, Defect,Free Single,Crystalline Films,ADVANCED MATERIALS, Issue 13 2006I. Vrejoiu Ferroelectric single,crystalline PbZr0.2Ti0.8O3 thin films, free from extended defects, are grown by pulsed laser deposition onto vicinal SrTiO3(001) single crystals. The PbZr0.2Ti0.8O3 films are strained and exhibit enhanced tetragonality, c/a,,,1.06. They have a remnant polarization, Pr,,,110,,C,cm,2, dielectric constant, ,33,,,90, and piezoelectric coefficient, d33, up to 50,pm,V,1 (see figure). [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] A New Chiral Schiff Base with Ferroelectric PropertyCHINESE JOURNAL OF CHEMISTRY, Issue 11 2008Xiu-Zhi LI Reaction of 1,1,1,5,5,5-hexafluoropen- tane-2,4-dione with (1S,2S)-(,)-1,2-diaminocyclohexane afforded a chiral Schiff base (1Z,4Z)-2,4-bis(trifluoromethyl)-5a,6,7,8,9,9a -hexahydro-3H -benzo[b][1,4]diazepine (1). Fluorescent analysis showed its intense emission band at 488 nm when the exciting radiation was set at 437 nm. Crystallographic analysis shows that it belongs to a non-centric space group C2 with ferroelectric behavior. A typical ferroelectric feature of electric hysteresis loop was obtained, with remanent polarization (Pr) of ca. 0.01 µC/cm2 and coercive field (Ec) of 0.27 kV/cm. [source] Photoresponsive Ferroelectric Liquid-Crystalline PolymersADVANCED FUNCTIONAL MATERIALS, Issue 1 2007P. Beyer Abstract The photoresponse of ferroelectric smectic side-chain liquid-crystalline (LC) polymers containing a photoisomerizable azobenzene derivative as a covalently linked photochromic side group is investigated. By static measurements in different photostationary states, the effect of trans,cis isomerization on the material's phase-transition temperatures and its ferroelectric properties (spontaneous electric polarization PS and director tilt angle ,) are analyzed. It turns out that the Curie temperature (transition SC* to SA) can be reversibly shifted by up to 17,°C. The molecular mechanism of this "photoferroelectric effect" is studied in detail using time-resolved measurements of the dye's optical absorbance, the director tilt angle, and the spontaneous polarization, which show a direct response of the ferroelectric parameters to the molecular isomerization. The kinetics of the thermal reisomerization of the azo dye in the LC matrix are evaluated. A comparison to the reisomerization reaction in isotropic solution (toluene) reveals a faster thermal relaxation of the dye in the LC phase. [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] Cationic disorder, microstructure and dielectric response of ferroelectric SBT ceramicsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-2 2003Ch. Muller Polycrystalline samples of SrBi2Ta2O9 (acronym SBT) have been prepared by means of solid-state reaction either using a classical route or by mechanochemical activation. For each compound, a structural analysis of the ferroelectric orthorhombic phase (space group A21am) has been performed from the fitting of neutron and/or X-ray powder diffraction data using the Rietveld method. A cationic disorder on Bi3+ and Sr2+ crystallographic sites has been revealed, the Sr atoms occupying the Bi sites and vice versa. From diffraction peak broadening analyses of high-resolution synchrotron X-ray diffraction data, it has been shown that the two grinding methods (manual or mechanical) induce local strains, the average apparent strain being three times larger for the mechanically ground sample. In order to link microstructure and ferroelectric properties, the dielectric constant has been measured as a function of the temperature. It appears that the position and the shape of the dielectric anomaly strongly depend upon the composition and the route used to elaborate the powders. More exactly, for the mechanically ground powder, the large apparent strain, probably correlated to the strong cation exchange revealed by the structural refinement, leads to a significantly enhanced dielectric response. [source] Lift-Off PMN,PT Thick Film for High-Frequency Ultrasonic BiomicroscopyJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010Benpeng Zhu Piezoelectric 0.65Pb(Mg1/3Nb2/3)O3,0.35PbTiO3 (PMN,35PT) thick film with a thickness of approximately 12 ,m has been deposited on the platinum-buffered Si substrate using a sol,gel composite method. The separation of the film from the substrate was achieved using a wet chemical method. The lifted-off PMN,35PT thick film exhibited good dielectric and ferroelectric properties. At 1 kHz, the dielectric constant and the dielectric loss were 3326 and 0.037, respectively, while the remnant polarization was 30.0 ,C/cm2. A high-frequency single-element acoustic transducer fabricated with this film showed a bandwidth at ,6 dB of 63.6% at 110 MHz. [source] Effect of BiScO3 and LiNbO3 on the Piezoelectric Properties of (Na0.5K0.5)NbO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Xueyi Sun Lead-free potassium sodium niobate-based piezoelectric ceramics (1,y)(Na0.5,0.5xK0.5,0.5xLix)NbO3,yBiScO3 ( y=0.01, x=0,0.06) have been prepared by an ordinary sintering process. The XRD analysis showed that the structure changes from orthorhombic to tetragonal with the increase of x (at y=0.01, abbreviated as KNNBSL100x). At room temperature, the polymorphic phase transition from the orthorhombic to the tetragonal phase was identified at approximately 0.02,x,0.04. The piezoelectric and ferroelectric properties were significantly enhanced. The temperature dependences of the relative permittivity revealed that the Curie temperature was increased with the addition of LiNbO3. These solid solution ceramics are promising as potential lead-free candidate materials. [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] Roles of Ba/Ti Ratios in the Dielectric Properties of BaTiO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2001Jung-Kun Lee The effect of the Ba/Ti ratio on microstructure, dielectric/ferroelectric properties, and domain width was studied using optical microscopy, ,(T) curves, D,E hysteresis, and transmission electron microscopy. Although Ti-excess samples showed abnormal grain growth and a decrease of room-temperature permittivity due to a liquid phase at grain boundaries, its ferroelectric properties were similar to those of stoichiometric BaTiO3 ceramics. However, in Ba-excess samples, an increase of permittivity and ferroelectric properties different from those of stoichiometry were found. Changes in domain width and ferroelectric transition behavior indicated that the variation of dielectric properties was related to the internal stress. It is proposed that this internal stress originated from differences in the thermal expansion coefficient between the matrix and the second phase. [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] Piezoelectric and ferroelectric properties of [(K0.4725Na0.4725)Li0.055]NbO3,(Ag0.5Li0.5)TaO3 lead-free ceramicsPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 5 2007Jiagang Wu Abstract New lead-free piezoelectric (1 , x)[(K0.4725Na0.4725)Li0.055]NbO3, x (Ag0.5Li0.5)TaO3 [(1 , x)KNNL,x ALT] ceramics were prepared by conventional sintering. Piezoelectric and ferroelectric properties and Curie temperature of the ceramics were studied. The (1 , x)KNNL,x ALT (x = 0.04) ceramics exhibit good properties (d33 , 252 pC/N, kp , 41%, TC , 471 °C, To,t = 47 °C, Pr = 33.1 ,C/cm2, Ec = 10.6 kV/cm). These results show that (1 , x)KNNL,x ALT (x = 0.04) ceramic is a promising lead-free piezoelectric material for high temperature application. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis of Novel Chiral and Acentric Coordination Polymers by the Reaction of Zinc or Cadmium Salts with Racemic 3-Pyridyl-3-aminopropionic AcidCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2004Zhi-Rong Qu Abstract Under hydrothermal (solvothermal) reaction conditions chiral compounds 1, 2, and 3 and one acentric compound 4 were obtained by the reaction of Zn2+ or Cd2+ with racemic 3-(3-pyridyl)-3-aminopropionic acid (rac -HPAPA). Compounds 1 and 2 crystallized in chiral space group P212121. At 105,°C, racemic 3-pyridyl-3-aminopropionic acid (rac -HPAPA) reacted with Zn(ClO4)2,6,H2O and dehydrogenated in situ to form the first chiral coordination polymer [Zn{(E)-3-C5H4NC(NH2)CHCOO}]ClO4 (1) with a ,-dehydroamino acid. Beyond 120,°C, the reaction of rac -HPAPA with Zn(ClO4)2,6,H2O deaminates in situ to form chiral coordination polymer [Zn{(E)-3-C5H4NCHCHCOO}(OH)] (2). At relatively low temperatures (70,°C), the solvothermal reaction of Zn(NO3)2,6,H2O with rac -HPAPA in methanol does not lead to any change in the ligand and results in the formation of a chiral (P212121) coordination polymer [Zn(papa)(NO3)] (3). The same reaction of Cd(ClO4)2,6,H2O with HPAPA also does not lead to any change in ligand and results in the formation of noncentric (Cc) coordination polymer [Cd(papa)(Hpapa)]ClO4,H2O (4). The network topology of both 1 and 3 is 10,3a, while 2 has a diamondoid-like (KDP-like, KDP=potassium dideuterophosphate) network. Particularly interesting from a topological perspective is that 4 has an unprecedented three-dimensional network. Compounds 1, 2, 3, and 4 are all second harmonic generation (SHG) active with 1 exhibiting the strongest response, while only 4 also displays good ferroelectric properties. [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] Structural and Electric Properties of Sol,Gel-Derived Ba0.9Sr0.1TiO3 MultilayersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2007X. K. Hong Crack-free Ba0.9Sr0.1TiO3 (BST) and Mn-doped Ba0.9Sr0.1TiO3 (BSTM) multilayers with thickness over 2 ,m have been prepared by chemical solution deposition based on one single precursor. Both multilayers exhibit good performance as Bragg reflectors. Mn doping tends to suppress the leakage current in BST multilayers effectively by smoothing the layers and the reduction of the charge carries. The Mn-doped BST multilayer displays an excellent ferroelectric property, with an average remnant polarization (Pr+,Pr,)/2 of 12.69 ,C/cm2 and an average coercive field (E+,E,)/2 of about 72.95 kV/cm under an applied field of 440 kV/cm. [source] | |||||||||||||||||||||||||