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1.
Bijun Fang Renbing Sun Keitaro Tezuka 《Journal of Physics and Chemistry of Solids》2009,70(5):893-899
Phase pure perovskite (1−x−y)Pb(Ni1/3Nb2/3)O3-xPb(Zn1/3Nb2/3)O3-yPbTiO3 (PNN-PZN-PT) ferroelectric ceramics were prepared by conventional solid-state reaction method via a B-site oxide mixing route. The PNN-PZN-PT ceramics sintered at the optimized condition of 1185 °C for 2 h exhibit high relative density and rather homogenous microstructure. With the increase of PbTiO3 (PT) content, crystal structure and electrical properties of the synthesized PNN-PZN-PT ceramics exhibit successive phase transformation. A morphotropic phase boundary (MPB) is supposed to form in (0.9−x)PNN-0.1PZN-xPT at a region of x=32-36 mol% confirmed by X-ray diffraction (XRD) measurement and dielectric measurement. The MPB composition can be pictured as providing a “bridge” connecting rhombohedral ferroelectric (FE) phase and tetragonal one since crystal structure of the MPB composition is similar to both the rhombohedral and tetragonal lattices. Dielectric response of the sintered PNN-PZN-PT ceramics also exhibits successive phase-transition character. 0.64PNN-0.1PZN-0.26PT exhibits broad, diffused and frequency dependent dielectric peaks indicating a character of diffused FE-paraelectric (PE) phase transition of relaxor ferroelectrics and 0.40PNN-0.1PZN-0.50PT exhibits narrow, sharp and frequency independent dielectric peaks indicating a character of first-order FE-PE phase transition of normal ferroelectrics. The FE-PE phase transition of 0.56PNN-0.1PZN-0.34PT is nearly first-order with some diffused character, which also exhibits the largest value of piezoelectric constant d33 of 462pC/N. 相似文献
2.
Ammonium dihydrogen phosphate NH4H2PO4 (ADP) is an antiferroelectric (AFE) compound belonging to the KDP-type family of hydrogen-bonded ferroelectrics. Recent ab initio results have shown that the optimization of the N–H–O bridges in ADP leads to the stabilization of the AFE state over a FE one. However, electron spin probe measurements have suggested that microregions of both phases may coexist above the critical antiferroelectric–paraelectric transition temperature. We have performed first principles studies of the energetics and relative stability of different AFE and FE defects embedded in a paraelectric (PE) matrix of ADP. Our analysis indicates that FE and AFE clusters are stable and may coexist in the PE phase, thus confirming the above suggestion. 相似文献
3.
Electromechanical-induced antiferroelectricben ferroelectric phase transition in PbLa(Zr,Sn,Ti)O3 ceramic
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Antiferroelectric—ferroelectric (AFE—FE) phase transition in ceramic Pb0.97La0.02(Zr0.75Sn0.136Ti0.114)O3 (PLZST) was studied by dielectric spectroscopy as functions of frequency (102—105 Hz) and pressure (0—500 MPa) under a DC electric field. The hydrostatic pressure-dependent remnant polarization and dielectric constant were measured. The results show that remnant polarization of the metastable rhombohedral ferroelectric PLZST poled ceramic decreases sharply and depoles completely at phase transition under hydrostatic pressure. The dielectric constant undergoes an abrupt jump twice during a load and unload cycle under an electric field. The two abrupt jumps correspond to two phase transitions, FE—AFE and AFE—FE. 相似文献
4.
Polycrystalline BiFeO3 (BFO) thin films were successfully grown on Pt/Ti/SiO2/Si(100) and SrTiO3 (STO) (100) substrates using the chemical solution deposition (CSD) technique. X‐ray diffraction (XRD) patterns indicate the polycrystalline nature of the films with rhombohedrally distorted perovskite crystal structure. Differential thermal analysis (DTA) was performed on the sol–gel‐derived powder to countercheck the crystal structure, ferroelectric (FE) to paraelectric (PE) phase transition, and melting point of bismuth ferrite. We observed a significant exothermic peak at 840 °C in DTA graphs, which corresponds to an FE–PE phase transition. Raman spectroscopy studies were carried out on BFO thin films prepared on both the substrates over a wide range of temperature. The room‐temperature unpolarized Raman spectra of BFO thin films indicate the presence of 13 Raman active modes, of which five strong modes were in the low‐wavenumber region and eight weak Raman active modes above 250 cm−1. We observed slight shifts in the lower wavenumbers towards lower values with increase in temperature. The temperature‐dependent Raman spectra indicate a complete disappearance of all Raman active modes at 840 °C corresponding to the FE–PE phase transitions. There is no evidence of soft mode phonons. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
5.
The electrical properties and phase transition behavior of (Pb0.87La0.02Ba0.1)(Zr0.6Sn0.4−xTix)O3 solid solutions (PLBZST, 0.04≤x0.2) were investigated by the X-ray diffraction, permittivity, pyroelectric current, and P-E electric hysterisis loops. As the composition x increased from 0.04 to 0.2, the antiferroelectric ceramics (x≤0.07, AFE) with tetragonal phase changed to the ferroelectric relaxors (RFE, 0.09≤x). AFE ceramics showed a peculiar diffuse phase transition and dielectric relaxation at the low temperature (down to −100 °C) due to a frustration between AFE and FE state. With an increase in composition x, electrically field-induced AFE-FE switching field (EAFE-FE) and AFE-paraelectric (PE) phase transition temperature (Tc) are depressed in the temperature (T)-Ti composition (x) phase diagram, a FE-AFE-PE triple phase point (Ttr) with the lowest transition temperature occurred at x=0.09. The pyroelectric currents under an application of various external electric field (E) were measured to identify a T-E phase diagram of the PLBZST compound. 相似文献
6.
Uniaxial strain induced ferroelectric phase transitions in rutile TiO2 are investigated by first-principles calculations. The calculated results show that the in-plane tensile strain induces rutile TiO2, paraelectric phase with P4-2/mnm (D4h) space group, to a ferroelectric phase with Pm (Cs) space group,driven by the softening behaviour of the E_u1 mode. In addition, the out-of-plane tensile strain, vertical to the ab plane, leads to a ferroelectric phase with P42nm (C4v) space group, driven by the softening behaviour of the A2u mode. The critical tensile strains are 3.7% in-plane and 4.0% out-of-plane, respectively. In addition, the in-plane compression strain, which has the same structure variation as out-of-plane tensile strain due to Poisson effect, leads the paraelectric rutile TiO2 to a paraelectric phase with Pnnm (D2h) space group driven by the softening behaviour of the B1g mode. These results indicate that the sequence ferroelectric (or paraelectric) phase depends on the strain applied. The origin of ferroelectric stabilization in rutile TiO2 is also discussed briefly in terms of strain induced Born effective charge transfer. 相似文献
7.
To describe the ferroelectric phase transition in ordered and disordered PbSc0.5Ta0.5O3 (PST) and PbSc0.5Nd0.5O3 (PSN) solid solutions, a model Hamiltonian is written in the local-mode approximation, in which long-range dipole-dipole
and short-range interactions of local modes are taken into account. The Hamiltonian parameters are determined from the set
of energies of a series of distorted structures, calculated within the nonempirical generalized Gordon-Kim model. The statistical
mechanics of the systems with a model Hamiltonian is investigated by the Monte Carlo method. It is revealed that PSN solid
solutions undergo a transition to the ferroelectric rhombohedral phase through an intermediate phase, existing in a narrow
temperature range. PST solid solutions undergo a ferroelectric phase transition directly from the paraelectric cubic to the
ferroelectric rhombohedral phase.
Original Russian Text ? V.I. Zinenko, N.G. Zamkova, 2008, published in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki,
2008, Vol. 133, No. 3, pp. 622–631. 相似文献
8.
We investigate the ferroelectric phase transition and domain formation in a periodic superlattice consisting of alternate ferroelectric (FE) and paraelectric (PE) layers of nanometric thickness. We find that the polarization domains formed in the different FE layers can interact with each other via the PE layers. By coupling the electrostatic equations with those obtained by minimizing the Ginzburg-Landau functional, we calculate the critical temperature of transition Tc as a function of the FE/PE superlattice wavelength Lambda and quantitatively explain the recent experimental observation of a thickness dependence of the ferroelectric transition temperature in KTaO3/KNbO3 strained-layer superlattices. 相似文献
9.
采用溶胶-凝胶法,在氧气氛中和层层晶化的工艺条件下,成功地制备了沉积在Pt/Ti/SiO2/Si(100)衬底上的铁电性能优良的Sr2Bi4Ti5O18 (SBTi)薄膜,并研究了SBTi薄膜的微结构、表面形貌、铁电性能和疲劳特性.研究表明:薄膜具有单一的层状钙钛矿结构,且为随机取向;薄膜表面光滑,无裂纹,厚度约为725nm;铁电性能测试显示较饱和、方形的电滞回线,当外电场强度为275kV/cm时
关键词:
溶胶-凝胶法
铁电薄膜
2Bi4Ti5O18')" href="#">Sr2Bi4Ti5O18 相似文献
10.
Janusz Przes?awski Bogus?aw Kosturek Ryszard Jakubas 《Solid State Communications》2007,142(12):713-717
Thermal (specific heat) and optical (linear birefringence) studies were performed for a new ferroelectric crystal (C3N2H5)5Bi2Cl11. Two phase transitions were confirmed and described. The first-order paraelastic-ferroelastic phase transition at 360 K was studied with a polarizing microscope. The continuous second-order phase transition at 165 K to the ferroelectric phase is described by the Landau model using specific heat and linear birefringence data. The Landau expansion coefficients B and C are of an order of magnitude higher than the closely related ferroelectric crystal; MAPCB — (CH3NH3)5Bi2Cl11. Thermal parameters (such as the excess enthalpy and the excess entropy ) of the continuous transition were estimated and discussed. The ‘two-site’ model describing the motion of three of the five imidazolium cations, which is proposed from the structural studies, is fully confirmed by the data from the ac-calorimetric measurements. 相似文献
11.
Site occupation of doping La3+ cations and phase transition in Na0.5Bi0.5TiO3–BaTiO3 solid solution
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The effects of La doping on the ferroelectric properties of 0.92Na0.5Bi0.5TiO3-0.08BaTiO3(NBT-BT) solid solution have been studied both experimentally and theoretically.The experimental results show that an abnormal ferro-toantiferroelectric phase transition is induced by La doping in NBT-BT.The first-principles calculations indicate that La3+ cations selectively substitute for the A site in NBT-BT as donors.Furthermore,the computed binding energy reveals that La cations is most likely to substitute Ba 2+or Na+,not Bi3+,at A site as donors in NBT-BT,as supported by our Raman spectra.The ferro-to-antiferroelectric phase transition of La-doped NBT-BT is believed to originate from the lattice aberrance and redistribution of valence electrons,thus strengthening the bonding of A-O,enhancing the hybridization between the A cation d orbital and O 2p orbital,and resulting in the deflection of the polar direction of NBT-BT lattice. 相似文献
12.
13.
The effect of hydrostatic pressure on the ferroelectric phase transition temperature in [NH2(CH3)2]3[Sb2Cl9] (DMACA) has been studied by electric permittivity measurements at pressures up to 400 MPa. The pressure-temperature phase diagram is given. The phase transition temperature (Tc) increases with increasing pressure up to 150 MPa, passes through a maximum and then decreases with a further increase of pressure. The unexpected nonlinear decrease in Tc with pressure increasing above 150 MPa suggests that the mechanism of ferroelectric phase transition in DMACA is different from hitherto assumed. 相似文献
14.
The crystal structure of the minor phase, named superstructure II, existing in multiferroic compound BiMnO3 has been studied by electron diffraction and high-resolution transmission electron microscopy. Domains of major and minor phases coexisting in BiMnO3 were observed in high-resolution electron microscope images. The unit cell of minor phase was determined to be triclinic with the size 4×4×4 times as large as the distorted perovskite subcell. The [111] and [101] projected structure maps of the minor phase have been derived from the corresponding images by means of the image processing. A possible rough three-dimensional (3D) structure model was proposed based on the 3D structural information extracted from the two projected structure maps. Since there is no inversion centre in the proposed model, the minor phase may contribute to the ferroelectric property of BiMnO3. 相似文献
15.
The difficulties in synthesizing phase pure BaTiO3 doped-(Na0.5Bi0.5)TiO3 are known. In this work, we reporting the optimized pulsed laser deposition (PLD) conditions for obtaining pure phase 0.92(Na0.5Bi0.5)TiO3-0.08BaTiO3, (BNT-BT0.08), thin films. Dielectric, ferroelectric and piezoelectric properties of BNT-BT0.08, thin films deposited by PLD on Pt/TiO2/SiO2/Si substrates are investigated in this paper. Perovskite structure of BNT-BT0.08 thin films with random orientation of nanocrystallites has been obtained by deposition at 600 °C. The relative dielectric constant and loss tangent at 100 kHz, of BNT-BT0.08 thin film with 530 nm thickness, were 820 and 0.13, respectively. Ferroelectric hysteresis measurements indicated a remnant polarization value of 22 μC/cm2 and a coercive field of 120 kV/cm. The piezoresponse force microscopy (PFM) data showed that most of the grains seem to be constituted of single ferroelectric domain. The as-deposited BNT-BT0.08 thin film is ferroelectric at the nanoscale level and piezoelectric. 相似文献
16.
PbYb1/2Ta1/2O3 single crystals were obtained for the first time. They were grown by the flux method. The PbOPbF2B2O3 system was used as a solvent. Dielectric investigations were carried out in 1 0 0c, 1 1 0c and 1 1 1c pseudocubic directions. These studies pointed to anisotropy of dielectric properties. Frequency-independent ε′(T) and ε″(T) maxima related to the antiferroelectric–paraelectric (AFE—PE) phase transition are observed for all directions at 562 K. The frequency-dependent ε′(T) and ε″(T) maxima near 400 K related to the ferroelectric (FE)–AFE phase transition are observed only in 1 1 1c direction. The hysteresis loops were observed in this direction only. These results point that ferroelectric relaxor properties appear only in 1 1 1c direction. We propose to consider the ferroelectric phase as ferrielectric one. 相似文献
17.
Wanwimon Banlue Naratip Vittayakorn 《Applied Physics A: Materials Science & Processing》2008,93(2):565-569
The solid solution between the antiferroelectric PbZrO3 (PZ) and relaxor ferroelectric Pb(Co1/3Nb2/3)O3 (PCoN) was synthesized by the columbite method. The phase structure and thermal properties of (1−x)PZ–xPCoN, where x=0.0–0.3, were investigated. With these data, the ferroelectric phase diagram between PZ and PCoN has been established. The
crystal structure data obtained from XRD indicates that the solid solution PZ–PCoN, where x=0.0–0.3, successively transforms from orthorhombic to rhombohedral symmetry with an increase in PCoN concentration. The AFE→FE
phase transition was found in the compositions of 0.0≤x≤0.10. The AFE→FE phase transition shift to lower temperatures with higher compositions of x. The width of the temperature range of FE phase was increased with increasing amount of PCoN. It is apparent that the replacement
of the Zr4+ ion by (Co1/3Nb2/3)4+ ions would decrease the driving force for antiparallel shift of Pb2+ ions, because they interrupt the translational symmetry. This interruption caused the appearance of a rhombohedral ferroelectric
phase when the amount of PCoN was more than 10 mol%. 相似文献
18.
The domain states and phase transitions in 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 single crystals were investigated by studying their relative permittivity under various dc bias at constant heating and cooling rates. The orientation dependence of the bias field effect was revealed by examining the temperature dependence of relative permittivity as a function of crystal orientation (the 〈111〉, 〈011〉 and 〈001〉 directions) and dc bias field. The crystals basically have a macrodomain rhombohedral ferroelectric state in the ferroelectric phase under zero dc bias. External bias field could modulate the domain state and induce a stable macrodomain state in the crystals. Also, it is proposed that the dc bias applied along the 〈001〉 or 〈011〉 direction could induce a tetragonal ferroelectric phase or an orthorhombic ferroelectric phase, respectively, in an intermediate temperature range. 相似文献
19.
Lead-free (Na0.5K0.5)NbO3-based piezoelectric ceramics were successfully fabricated by substituting with a small amount of BiFeO3 (BF). Difficulty in sintering of pure NKN ceramics can be eased by adding a few molar percent of BF, and the crystalline structure is also changed, leading to a morphotropic phase boundary (MPB) between ferroelectric orthorhombic and rhombohedral phases. The MPB exists near the 1-2 mol% BF-substituted NKN compositions, exhibiting enhanced ferroelectric, piezoelectric, and electromechanical properties of Pr=23.3 μC/cm2, d33=185 pC/N, and kp=46%, compared to an ordinarily sintered pure NKN ceramics. The MPB composition has a Curie temperature of ∼370 °C, comparable to that of some commercial PZT materials. 相似文献
20.
A. M. Abakumov O. I. Lebedev L. Nistor G. Van Tendeloo S. Amelinckx 《Phase Transitions》2013,86(2):143-160
The paraelectric-ferroelectric (PE-FE) phase transition in stuffed tridymite BaAl2O4 was studied in situ by transmission electron microscopy. Electron diffraction revealed that the PE and FE phases have hexagonal symmetry. The PE-FE phase transition is accompanied by a doubling of the cell dimensions in the a-b plane. The transition is reversible, takes place over a wide temperature range (400–670 K.) and the interfaces related to the transition have a fluctuating character. The crystal structure of the high temperature PE phase was determined by high resolution electron microscopy. The structures of the PE phase (space group P6322, a≈ 5.22 Å, c ≈ 8.8 Å) and of the FE phase (space group P63, a= 10.4469(1)Å, c = 8.7927(1)Å) differ mainly by the configuration of the Al-O strings oriented along the c-axis. In the PE phase all the strings are equivalent whereas straight and corrugated strings alternate in an ordered manner in the FE phase resulting in doubling of the a and b cell parameters. Translation and orientation domains due to the decrease of the translation and point symmetry were frequently observed. 相似文献