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1.
2.
《Materials Letters》2005,59(14-15):1929-1931
A precipitate was formed when an aqueous solution of BaCl2, NbF5 and urea in required ratio (the ratio of total metal cations to the urea is five) is heated on a water bath at 100 °C. This precipitate on decomposition at 600 °C yielded the nanocrystallites of BaNb2O6 (BN), as confirmed by X-ray diffraction study (XRD). This is a much lower temperature as compared to that prepared by traditional solid state method (1000° C) as reported for the formation of BaNb2O6. Transmission electron microscope (TEM) investigations revealed that the average particle size is 85 nm for the calcined powders. The room temperature dielectric constant at 1 kHz is found to be 900. The ferroelectric hysteresis loop parameters of these samples were also studied. 相似文献
3.
《Materials Letters》2004,58(27-28):3474-3476
A simple coprecipitation technique had been successfully applied for the preparation of pure ultrafine single-phase CaBi2Ta2O9 (CBT). Ammonium hydroxide and ammonium oxalate were used to precipitate Ca2+, Bi3+ and Ta5+ cations simultaneously. No pyrochlore phase was found while heating powder at 800 °C and pure CaBi2Ta2O9 phase was found to be formed by XRD. Particle size and morphology was studied by transmission electron microscopy (TEM). The room temperature dielectric constant at 1 kHz is 100. The ferroelectric hysteresis loop parameters of these samples were also studied. 相似文献
4.
《Materials Research Bulletin》2003,38(11-12):1601-1605
A simple co-precipitation technique had been successfully applied for the preparation of pure ultrafine single phase SrBi2Ta2O9. Ammonium hydroxide was used to precipitate Sr2+, Bi3+ and Ta5+ cations simultaneously. No pyrochlore phase was found while heating powder at 800 °C and pure SrBi2Ta2O9 phase was found to be formed by X-ray diffraction. Particle size and morphology was studied by scanning electron spectroscopy. Ferroelectric hysteresis loop parameters of these samples were also studied. 相似文献
5.
A. A. Grabar 《Technical Physics Letters》1997,23(8):635-637
The occurrence of light scattering during light transmission is described for some orientations of an incident laser beam
in polydomain crystals of the uniaxial ferroelectric tin thiohypodiphosphate. This scattering is probably caused by the presence
of a reflecting layer near the 180° domain walls. A reflecting layer may be formed as a result of the appearance of charged
nonparallel domain walls.
Pis’ma Zh. Tekh. Fiz. 23, 45–50 (August 26, 1997) 相似文献
6.
Fine powders of orthorhombic bismuth vanadate (Bi2 VO5·5) have been synthesized by coprecipitation method. Powder X-ray diffraction and electron microscopic techniques have been
used to characterize these samples. The formation of the monophasic Bi2 VO5·5 was confirmed. The compacted powders sintered at 1070K have been characterized for their dielectric properties as a function
of both temperature (300–900 K) and frequency (100 Hz–10 MHz) and found to be superior to those obtained by the conventional
solid-state reaction route. 相似文献
7.
Europium substituted samples of compositions Sr1 − xEuxBi2Ta2O9 were synthesized by solid-state reaction method. The prepared samples were characterized for their structural and electrical properties. X-ray analysis confirms the formation of the single-phase layered perovskite structure. The microstructural studies reveal that the average grain size increases with increase in Eu content. An increase in remanent polarization and d33 values with increasing concentration of europium has been observed. The maximum 2Pr ~ 14 μC/cm2 is observed in the sample with x = 0.20. The observed results have been discussed in terms of contribution from the cation vacancies introduced into the lattice structure due to donor doping. 相似文献
8.
N. N. Kolpakova I. L. Shul’pina L. Shchepan’ska P. Piskunovich 《Technical Physics Letters》1997,23(12):972-974
An analysis of the thermally induced domain behavior in Cd2Nb2O7 under cooling and heating in the dark has revealed that below T
c
the coexistence of ferroelectric-ferroelastic domains of different types is accompanied by irreversible changes in the domains
of the previous phase (T
c
<T<T
s
). Interaction of domains with dislocations and other lattice defects causes thermal hysteresis in the phase transition region
near T
s
and T
c
typical of the “superheated” ferroic state.
Pis’ma Zh. Tekh. Fiz. 23, 64–69 (December 26, 1997) 相似文献
9.
Shihai Zhang Rob J. Klein Kailiang Ren Baojin Chu Xi Zhang James Runt Q. M. Zhang 《Journal of Materials Science》2006,41(1):271-280
To elucidate the molecular origin of the polarization dynamics in the ferroelectric relaxor poly(vinylidene fluoride—trifluoroethylene-chlorofluoroethylene)
(P(VDF-TrFE-CFE)) terpolymer, a broadband dielectric study was carried out in the frequency range from 0.01 Hz to 10 MHz and
temperatures from −150°C to 120°C for the terpolymer and a normal ferroelectric P(VDF-TrFE) copolymer. The relaxation processes
were also studied using dynamic mechanical analysis. It was shown that in the terpolymer, which was completely converted to
a ferroelectric relaxor, there is no sign of the relaxation process associated with the ferroelectric-paraelectric transition
which occurs in the P(VDF-TrFE) copolymer. In the copolymer, three additional relaxation processes have been observed. It
was found that the relaxation process βa, which was commonly believed to be associated with the glass transition in the amorphous phase, in fact, contains significant
contribution from chain segment motions such as domain boundary motions in the crystalline region. In the temperature range
studied, the terpolymer exhibits the latter three relaxation processes with the one (termed βr) near the temperature range of βa significantly enhanced. This is consistent with the observation that in conversion from the normal ferroelectric to a ferroelectric
relaxor, the macro-polar domains are replaced by nano-polar-clusters and the boundary motions as well as the reorientation
of these nano-clusters generate the high dielectric response. The experimental data also reveal a broad relaxation time distribution
related for the βr process whose distribution width increases with reduced temperature, reflecting the molecular level heterogeneity in the
crystalline phase due to the random introduction of the CFE monomer in the otherwise ordered macro-polar domains. The random
interaction among the nano-clusters as well as the presence of the random fields produces ferroelectric relaxor behavior in
the terpolymer. 相似文献
10.
Device modeling of ferroelectric memory field-effect transistor for the application of ferroelectric random access memory 总被引:2,自引:0,他引:2
Lue HT Wu CJ Tseng TY 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2003,50(1):5-14
An improved theoretical analysis on the electrical characteristics of ferroelectric memory field-effect transistor (FeMFET) is given. First, we propose a new analytical expression for the polarization versus electric field (P-E) for the ferroelectric material. It is determined by one parameter and explicitly includes both the saturated and nonsaturated hysteresis loops. Using this expression, we then examine the operational properties for two practical devices such as the metal-ferroelectric-insulator-semiconductor field-effect transistor (MFIS-FET) and metal-ferroelectric-metal-insulator-semiconductor field-effect transistor (MFMIS-FET) as well. A double integral also has been used, in order to include the possible effects due to the nonuniform field and charge distribution along the channel of the device, to calculate the drain current of FeMFET. By using the relevant material parameters close to the (Bi, La)/sub 4/Ti/sub 3/O/sub 12/ (BIT) system, accurate analyses on the capacitors and FeMFET's at various applied biases are made. We also address the issues of depolarization field and retention time about such a device. 相似文献
11.
Dielectric properties and microstructural characteristics of ferroelectric bismuth vanadate (Bi2VO5.5) ceramics exhibiting grain sizes of 7, 10, 20 and 25 m have been studied. Microstructural studies indicate the presence of ferroelectric 90° domain patterns on the surface as well as in the bulk of the coarse-grained ceramics. The dielectric constant and the loss tangent both at room temperature and in the vicinity of the Curie temperature have been found to increase with increasing grain size. The Curie temperature (725 K) is found to shift slightly (by about 7 K) towards higher temperatures as the grain size increases (7–25 m). The magnitude of the dielectric anomaly around 725 K is found to be higher for coarse-grained ceramics. The dielectric constant and the loss have been found to decrease with increase in frequency (1–100 kHz) for all the ceramics studied. The increase in dielectric constant with increasing grain size is attributed to a decrease in thickness of the relatively more insulating grain boundary layer. 相似文献
12.
Suchaneck G Vidyarthi VS Gerlach G Solnyshkin AV Kislova IL 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2007,54(12):2555-2561
In this work, a ferroelectric domain-enhanced electron emission mechanism is proposed. The polarization distribution near 90 degrees domain walls is calculated by solving a set of second order differential equations, including the Poisson's one and equations derived from an expansion of the free energy Phi(P) in power series of the polarization according to the Devonshire-Landau-Ginzburg theory. Domain walls intersecting the emitting surface cause sufficient electric fields and lower the potential barrier for electron emission. This induces centers of enhanced electron emission. Relaxing domain walls were found to excite trapped excess electrons in front of the wall. 相似文献
13.
Numerical analysis of ferroelectric/ferroelastic domain switching in ferroelectric ceramics 总被引:1,自引:0,他引:1
A numerical approach predicting the behavior of ferroelectric ceramics under electric field and mechanical loading is proposed in this paper. In the model, macroscopic properties of ferroelectric ceramics are determined by microscopic structures. Ferroelectric ceramics are seen to be composed of many domains with different orientations, and domain switching is the source of the nonlinear constitutive behavior of the ferroelectric ceramics. Numerical calculations based on the model were carried out, and the computational results are compared with the experimental results, which shows the two sets of results consist with each other. The calculation approach can provide a guidance for the ceramics component design. 相似文献
14.
N. N. Kolpakova M. Wiesner A. O. Lebedev P. P. Syrnikov V. A. Khramtsov 《Technical Physics Letters》1998,24(9):679-682
It is shown that accidental impurities and structural defects (cation vacancies) formed in the (CdO8)
n−2 sublattice during synthesis enhance the relaxation properties of the system near T
Curie and suppress the ferroelectric phase transition.
Pis’ma Zh. Tekh. Fiz. 24, 36–44 (September 12, 1998) 相似文献
15.
A gel was formed when a aqueous solution of BaCl2, NbF5 and citric acid in stoichiometric ratio is heated on a water bath. This gel on decomposition at 600°C yielded the nano crystallites
of BaNb2O6, as confirmed by X-ray diffraction study (XRD). This is a much lower temperature as compared to that prepared by traditional
solid state method (1000°C) as reported for the formation of BaNb2O6. Transmission electron microscopic (TEM) investigations revealed that the average particle size is 50 nm for the calcined
powders. The room temperature dielectric constant at 1 kHz is found to be 1000. The ferroelectric hysteresis loop parameters
of these samples were also studied. 相似文献
16.
F.M. Hashimzade G.S. Orudzhev A.M. Ulubey K.R. Allakhverdiev 《Materials Research Bulletin》2010,45(10):1438-1442
We present the first-principles calculation of the lattice dynamics of the TlGaSe2 ternary semiconductor having highly anisotropic crystal structure. Calculations have been performed using open-source code ABINIT on the basis of the density functional perturbation theory within the plane-wave pseudopotential approach. Results on the frequencies of phonon modes in the centre of Brilloin zone and the dispersion of transverse shear acoustic branch of the phonon spectra agree well with the experimental data on Raman scattering, infrared reflectivity and ultrasound wave propagation in TlGaSe2. The calculated and experimental temperature dependencies of heat capacity are in a good agreement up to the room temperature. Along the layer, the low-frequency acoustic branch displays the bending wave behavior which is characteristic of the layer crystal structures. 相似文献
17.
18.
We report the first observation of piezoelectricity and ferroelectricity in individual Sb(2)S(3) nanowires embedded in anodic alumina templates. Switching spectroscopy-piezoresponse force microscopy (SS-PFM) measurements demonstrate that individual, c-axis-oriented Sb(2)S(3) nanowires exhibit ferroelectric as well as piezoelectric switching behavior. Sb(2)S(3) nanowires with nominal diameters of 200 and 100 nm showed d(33(eff)) values around 2 pm V(-1), while the piezo coefficient obtained for 50 nm diameter nanowires was relatively low at around 0.8 pm V(-1). A spontaneous polarization (P(s)) of approximately 1.8 μC cm(-2) was observed in the 200 and 100 nm Sb(2)S(3) nanowires, which is a 100% enhancement when compared to bulk Sb(2)S(3) and is probably due to the defect-free, single-crystalline nature of the nanowires synthesized. The 180° ferroelectric monodomains observed in Sb(2)S(3) nanowires were due to uniform polarization alignment along the polar c-axis. 相似文献
19.
Science and technology of ferroelectric films and heterostructures for non-volatile ferroelectric memories 总被引:7,自引:0,他引:7
We present in this article a review of the status of thin film ferroelectric materials for nonvolatile memories. Key materials issues relevant to the integration of these materials on Si wafers are discussed. The effect of film microstructure and electrode defect chemistry on the ferroelectric properties relevant to a high density nonvolatile memory technology are discussed. The second part of this review focuses on approaches to integrate these capacitor structures on a filled poly-Si plug which is a critical requirement for a high density memory technology. Finally, the use of novel surface probes to study and understand broadband polarization dynamics in ferroelectric thin films is also presented. 相似文献
20.
H Schmid 《Bulletin of Materials Science》1994,17(7):1411-1414
In the form of a succinct overview the structure and symmetry requirements of magnetic ferroelectrics are discussed. Boracites
are the best-studied examples and have phases being simultaneously ferroelectric, ferromagnetic and ferroelastic. One of the
salient features of such materials is the obligatory occurrence of the linear and bilinear magnetoelectric effects. They represent
an invaluable auxiliary information for magnetic symmetry determination by neutron diffraction. Owing to the complexity of
property combinations, work with single crystals and polarized light microscopy is obligatory. Key references of the field
are given. 相似文献