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1.
Ground state and properties of ferroelectric superlattices based on crystals of the perovskite family 总被引:1,自引:0,他引:1
A. I. Lebedev 《Physics of the Solid State》2010,52(7):1448-1462
The crystal structure of the ground state of ten free-standing ferroelectric superlattices based on crystals with the perovskite
structure (BaTiO3/SrTiO3, PbTiO3/SrTiO3, PbTiO3/PbZrO3, SrZrO3/SrTiO3, PbZrO3/BaZrO3, BaTiO3/BaZrO3, PbTiO3/BaTiO3, BaTiO3/CaTiO3, KNbO3/KTaO3, and KNbO3/NaNbO3) was calculated from first principles within the density functional theory taking into account criteria for stability of
the structures with respect to acoustic and optical distortions. It was shown that the ground state in all the considered
superlattices corresponds to the ferroelectric phase. It was found that the polarization vector has a tendency toward a tilt
to the plane of the superlattice layers, which makes it possible to decrease the electrostatic and elastic energy in the superlattices
consisting of materials with different ferroelectric properties. The importance of the inclusion of structural distortions
due to unstable phonons at the Brillouin zone boundary, which, in a number of cases, lead to significant changes in ferroelectric
and dielectric properties of the superlattices, was demonstrated. 相似文献
2.
A. I. Lebedev 《Physics of the Solid State》2009,51(11):2324-2333
The phonon spectrum; crystal structure of the polar phase; spontaneous polarization; dielectric constant, piezoelectric, and
elastic moduli tensors for free_standing and substrate_supported superlattices mBaTiO3/nSrTiO3 (with m = n = 1–4) were calculated within the density functional theory. The simulation of properties of the disordered Ba0.5Sr0.5TiO3 solid solution using two special quasirandom SQS-4 structures and their comparison with the properties of the superlattices
revealed a tendency of the BaTiO3-SrTiO3 system to superstructure ordering and showed that the superlattices are thermodynamically quite stable. The ground state
of the free-standing superlattice corresponds to the monoclinic polar phase Cm, which transforms to the tetragonal polar phase P4mm under in-plane compressive strain of the superlattice and to the orthorhombic polar phase Amm2 under in-plane tensile strain. With a change in the in-plane lattice parameter, in the vicinity of boundaries between neighboring
polar phases, some optical and acoustic modes soften and some components of the static dielectric constant, piezoelectric,
and elastic moduli tensors diverge critically. 相似文献
3.
Y. Zhou 《Solid State Communications》2010,150(29-30):1382-1385
I studied theoretically the enhancement of remanent polarization and dielectric permittivity of interfacial-coupled ferroelectric superlattices based on the Landau–Ginzburg theory. Our model adopts the Landau–Khalatnikov equation to describe hysteresis behavior and takes the time-dependent space-charge-limited conductivity into account to investigate the ferroelectric and dielectric properties of ferroelectric superlattices. The results are in good agreement with recent experimental observations on the enhancement of remanent polarization and permittivity of BaTiO3/SrTiO3 superlattices and heterolayered Pb(Zr,Ti)O3 thin films. 相似文献
4.
The 3D dependences ?′(log f, T) and tanδ(logf, T) of a perfect BaTiO3 single crystal grown by the Remeika method have been studied in the ranges f = 1–2 × 107 Hz and T = ?80–130°C. These dependences characterize a transition from the paraelectric phase (121.5°C) as a near-antiferroelectric transition followed by the transition to the tetragonal phase at ~79.5°C. According to a number of signs, the range 121.5–79.5°C corresponds to a metastable phase typical of first-order phase transitions. The unexpected result of this work has been discussed with invoking the hypothesis on the BaTiO3 structure in the paraelectric phase, according to which it consists of three antiferroelectric states oriented along the crystallographic axes. Using the dielectric properties of BaTiO3 as an example, the method of direct correct determination of the temperatures of the structural transformations from the anomaly of tanδ(logf, T) has also been demonstrated. 相似文献
5.
A. Visinoiu R. Scholz M. Alexe D. Hesse 《Applied Physics A: Materials Science & Processing》2005,80(2):229-235
Epitaxial BaTiO3 films and epitaxial BaTiO3/SrTiO3 multilayers were grown by pulsed laser deposition on vicinal surfaces of (001)-oriented Nb-doped SrTiO3 (SrTiO3:Nb) single-crystal substrates. Atomic force microscopy was used to investigate the surface topography of the deposited films. The morphology of the films, of the BaTiO3/SrTiO3 interfaces, and of the column boundaries was investigated by cross-sectional high-resolution transmission electron microscopy. Measurements of the dielectric properties were performed by comparing BaTiO3 films and BaTiO3/SrTiO3 multilayers of different numbers of individual layers, but equal overall thickness. The dielectric loss saturates for a thickness above 300 nm and linearly decreases with decreasing film thickness below a thickness of 75 nm. At the same thickness of 75 nm, the thickness dependence of the dielectric constant also exhibits a change in the linear slope both for BaTiO3 films and BaTiO3/SrTiO3 multilayers. This behaviour is explained by the change observed in the grain morphology at a thickness of 75 nm. For the thickness dependence of the dielectric constant, two phenomenological models are considered, viz. a series-capacitor model and a dead-layer model. PACS 77.22.-d; 77.22.Ch; 77.55.+f; 77.22.Gm; 77.84.Dy; 81.15.-z ; 81.16.Mk; 81.65.-b; 68.55.-a; 68.37.-d 相似文献
6.
7.
The far-infrared optical and dielectric properties of ferroelectric perovskite titanate powder BaTiO3 are reported. The terahertz time-domain spectroscopy (THz-TDS) measurement reveals that the low frequency dielectric response of BaTiO3 is closely related to the lowest pair of transverse optical (TO) and longitudinal optical (LO) modes near at 180 cm−1, which is verified by Raman spectroscopy. This result provides a better understanding of the relation of low-frequency dielectric function with the optical phonon mode for ferroelectric materials. Combining terahertz TDS with Raman spectra, the overall low frequency optical phonon response of BaTiO3 is presented in an extended spectral range from 6.7 to 1200 cm−1. 相似文献
8.
Yu Feng Can Wang ShiLu Tian Yong Zhou Chen Ge HaiZhong Guo Meng He KuiJuan Jin GuoZhen Yang 《中国科学:物理学 力学 天文学(英文版)》2017,60(6):067711
BiFeO3 (BFO) thin films with BaTiO3 (BTO) or SrTiO3 (STO) as buffer layer were epitaxially grown on SrRuO3-covered SrTiO3 substrates. X-ray diffraction measurements show that the BTO buffer causes tensile strain in the BFO films, whereas the STO buffer causes compressive strain. Different ferroelectric domain structures caused by these two strain statuses are revealed by piezoelectric force microscopy. Electrical and magnetical measurements show that the tensile-strained BFO/BTO samples have reduced leakage current and large ferroelectric polarization and magnetization, compared with compressively strained BFO/STO. These results demonstrate that the electrical and magnetical properties of BFO thin films can be artificially modified by using a buffer layer. 相似文献
9.
The effect of calcium substitution on the structural, dielectric, ferroelectric, piezoelectric, and energy storage properties of BaTiO3 (BT) ceramics has been investigated. XRD confirmed the phase formation of Barium Calcium Titanate (BCT), and structural Rietveld refinement was used to estimate the lattice parameters. It is evident from the SEM data that the average grain size decreases as calcium is added. At Curie temperature (110 °C), BCT 0.10 ceramic has a good dielectric constant of 15834 and a very low dielectric loss of 0.009. According to the ferroelectric and piezoelectric investigations, BCT 0.10 exhibits maximum spontaneous polarization with the highest piezoelectric charge coefficient of 100 pC/N. BCT 0.10 has a maximum energy storage density of 96.8 mJ/cm3 and a good energy storage efficiency of 53.9%, which is around three times that of pure BaTiO3. These results suggest that the BCT ceramic has good potential for energy storage applications. 相似文献
10.
The structure and dielectric characteristics of the (1000 nm)SrTiO3 spacer in a (001)SrRuO3 ‖ (001)SrTiO3 ‖ (001)La0.67Ca0.33MnO3 trilayer heterostructure grown on a (001)(LaAlO3)0.3+(Sr2AlTaO6)0.7 substrate have been studied. Both oxide electrodes, as well as the strontium titanate layer, were cube-on-cube epitaxially grown. The unit cell parameter in the SrTiO3 layer measured in the substrate plane (3.908±0.003 Å) practically coincided with that determined along the normal to the substrate surface (3.909±0.003 Å). The temperature dependence of the real part of the permittivity ?′ of the SrTiO3 layer in the range 70–180 K fits the relation (?′)?1 ~ ? 0 ?1 C 0 ?1 (T-T C ) well, where C0 and TC are the Curie constant and the Curie-Weiss temperature, respectively, for bulk strontium titanate crystals and ?0 is the free-space permittivity. The data obtained on the temperature dependence of the permittivity of SrTiO3 films enabled us to evaluate the effective depth of electric field penetration into the manganite electrode (L e ≈ 0.5 nm) and the corresponding capacitance (C e ≈1×10?6 F/cm2) of the interface separating the (001)SrTiO3 layer from the (001)La0.67Ca0.33MnO3 bottom electrode. 相似文献
11.
A. M. Parshin V. A. Gunyakov V. Ya. Zyryanov V. F. Shabanov 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(8):1045-1048
The change in the domain texture of the 5CB nematic liquid crystal on the surface of a polyvinyl butyral gelatinous polymer
solution cured in a magnetic field is studied optically. The alignment of the nematic is described by the effective order
parameter S* of the polydomain cells. The anchoring energy of a liquid crystal with gelatinous polymer W
ϕ = 1 × 10−3 erg/cm2 is determined. 相似文献
12.
13.
Ch. Schwan F. Martin G. Jakob J.C. Martinez H. Adrian 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(3):477-481
We have investigated the crystal structure and the ferroelectric properties of BaTiO3 thin films with YBa2Cu3O as the bottom and Au as the top electrode. Epitaxial heterostructures of YBa2Cu3O and BaTiO3 were prepared by dc and rf sputtering, respectively. The crystal structure of the films was characterised by X-ray diffraction.
The ferroelectric behaviour of the BaTiO3 films was confirmed by hysteresis loop measurements using a Sawyer Tower circuit. We obtain a coercive field of 30 kV/cm
and a remanent polarisation of 1.25 μC/cm2. At sub-switching fields the capacitance of the films obeys a relation analogous to the Rayleigh law. This behaviour indicates
an interaction of domain walls with randomly distributed pinning centres. At a field of 5 MV/m we calculate a 3% contribution
of the irreversible domain wall motion to the total dielectric constant.
Received 24 June 1999 and Received in final form 27 August 1999 相似文献
14.
采用脉冲激光沉积(PLD)镀膜技术在倾斜10°的LaAlO3(100)单晶衬底上制备了(SrTiO3)n/(SrTi0.8Nb0.2O3)m系列超晶格.在超晶格薄膜的XRD图谱中清楚地观察到周期调制的卫星峰结构.从卫星峰的分布计算了超周期,进而得到了在生长SrTiO3和SrTi0.8Nb0.2<
关键词:
3)n/(SrTi0.8Nb0.2O3)m]20/LAO(100)超晶格')" href="#">[(SrTiO3)n/(SrTi0.8Nb0.2O3)m]20/LAO(100)超晶格
激光感生热电电压
各项异性Seebeck系数
原子层热电堆 相似文献
15.
We have performed first principles calculations of Fe-doped BaTiO3 and SrTiO3. Dopant formation energy, structure distortion, band structure and density of states have been computed. The dopant formation energy is found to be 6.8eV and 6.5eV for Fe-doped BaTiO3 and SrTiO3 respectively. The distances between Fe impurity and its nearest O atoms and between Fe atom and Ba or Sr atoms are smaller than those of the corresponding undoped bulk systems. The Fe defect energy band is obtained, which mainly originates from Fe 3d electrons. The band gap is still an indirect one after Fe doping for both BaTiO3 and SrWiO3, but the gap changes from Γ-R point to Γ-X point. 相似文献
16.
Kenji Yoshii Yasuhiro Yoneda Ignace Jarrige Tatsuo Fukuda Yasuo Nishihata Chikashi Suzuki Yoshiaki Ito Takahito Terashima Shinzo Yoshikado Sei Fukushima 《Journal of Physics and Chemistry of Solids》2014
We have studied the electronic properties of the ferroelectric barium titanate BaTiO3 using two complementary bulk-sensitive spectroscopic probes, resonant X-ray emission spectroscopy (RXES) and X-ray absorption spectroscopy in the partial fluorescence mode (PFY-XAS) at the Ba-L3 and Ti-K absorption edges. Contrary to a previous study, we found no fine structure in the pre-edge area of the PFY-XAS spectrum at the Ba-L3 edge, and no temperature-induced spectral change was observed between room temperature and 150 °C. This result is not supportive of the possible presence of the displacement around Ba2+ at the Curie temperature. RXES spectra were measured at the Ti-K edge for BaTiO3, along with SrTiO3 and La-doped metallic SrTiO3. The photon energy of the emission peak is found to be nearly constant throughout the absorption edge for all three compounds. We deduce the Ti 3d states to have a delocalized character, in contrast with the Ba 5d states, a property which is consistent with the proposed scenario of the formation of electric dipoles in BaTiO3. 相似文献
17.
A. Yu. Emel’yanov 《Physics of the Solid State》2001,43(2):329-336
The influence of the domain boundary width on the statics of single 90° elastic domains (twins) in epitaxial ferroelectric tetragonal films grown on a cubic substrate is theoretically investigated. The inhomogeneous internal stresses arising in polydomain epitaxial systems are calculated by the effective dislocation method. The elastic energy stored in the heterostructure is determined. The equilibrium domain size is found and the stability diagram for single domains at different wall widths is constructed by minimizing the total internal energy of the system. It is demonstrated that, as the domain boundary width 2w increases, the stability region of 90° domains increases and qualitatively changes for ultrathin films when the parameter 2w exceeds the specific critical value 2w cr. The equilibrium width 2w* of domain walls in thin films is predicted to be larger compared to the width 2w 0 of domain boundaries in a macroscopic crystal. 相似文献
18.
Based on the phenomenological Landau-Devonshire theory, we investigate the film thickness dependence of ferroelectric and electro-optic properties of epitaxial BaTiO3 thin films grown on SrTiO3 and MgO substrates. By using the effective substrate lattice parameter concept, the film thickness dependence of misfit strain is incorporated into the theory. Therefore, the film thickness dependence of ferroelectric and electro-optic properties in epitaxial BaTiO3 thin films can be explained. Moreover, a large quadratic electro-optic effect was obtained in the BaTiO3 thin films, which is in good agreement with the experimental result of BaTiO3 thin films on the MgO substrate. 相似文献
19.
O. A. Maslova Yu. I. Yuzyuk N. Ortega A. Kumar R. S. Katiyar 《Physics of the Solid State》2011,53(5):1062-1066
A series of BaTiO3/Ba1 ? x Sr x TiO3 (BT/BST) superlattices were prepared by pulsed laser deposition on MgO substrates with a constant period of 80 Å (40 Å BT and 40 Å BST) and varying compositions of the BST layer so that the Ba/Sr concentration ratios were 0/100, 30/70, 40/60, 50/50, 60/40, 70/30, 100/0. The soft mode E(1TO) of the polarized Raman spectra transformed depending on the Ba/Sr ratio in the BST layer. As the Sr concentration in the BST layers increased from 0 to 100%, the E(1TO) soft mode half-width varied from 171 to 103 cm?1 and its frequency increased from 31 to 109 cm?1 due to the interaction between the epitaxial layers forming the superlattices. 相似文献
20.
From measurements of the differential resistance for tunneling junctions prepared from SrTiO3?x and In(Bi) electrodes with Schottky tunneling barriers the superconducting energy gap of SrTi O3?x(n = 3 × 1019 cm?3) is derived. We find indications for the fact that the 1.9 meV soft phonon mode Γ5+ in tetragonal SrTiO3 is important for the effective electron-electron interaction in superconducting SrTiO3?x. 相似文献