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The dielectric, optical, and electro-optical properties of transparent ferroelectric ceramics 75PbMg1/3Nb2/3O3-25PbTiO3 (75PMN-25PT) with different La concentrations (2, 3, and 4 at %) have been studied. It has been shown that all the samples
under study undergo a diffuse phase transition, and the degree of diffuseness increases with an increase in the La concentration.
The temperature dependences of the optical transmission in different regimes of applying an electric field and the quadratic
electro-optical effect have been investigated. It has been found that, at room temperature, the maximum electro-optical effect
is observed in the ceramics with a La concentration of 3 at %. This is explained by the fact that the measurement temperature
is close to the Vogel-Fulcher temperature at which the minimum electric field is required to induce ferroelectric states from
the relaxor phase. 相似文献
3.
The temperature dependence of the elongation per unit length for Pb(Mg1/3Nb2/3)O3 crystals unannealed after growth and mechanical treatment is investigated in the course of thermocycling. It is revealed that this dependence deviates from linear behavior at temperatures below 350°C. The observed deviation is characteristic of relaxors, is very small in the first cycle, increases with increasing number n of thermocycles, and reaches saturation at n≥3. In the first cycle, a narrow maximum of the acoustic emission activity is observed in the vicinity of 350°C. In the course of thermocycling, the intensity of this maximum decreases and becomes zero at n>3. For (1?x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 crystals, the dependence of the temperature of this acoustic emission maximum on x exhibits a minimum. It is assumed that the phenomena observed are associated with the phase strain hardening due to local phase transitions occurring in compositionally ordered and polar nanoregions. 相似文献
4.
O. N. Ivanov E. A. Skripchenko I. P. Raevskii S. P. Kubrin 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(10):1392-1394
Peculiarities in the behavior of the dielectric, elastic, and anelastic properties of the PbFe1/2Nb1/2O3 ceramic ferroelectromagnet have been found and investigated near the antiferromagnetic phase transition (Néel temperature T N = 160 K). It is established that the transition to the antiferromagnetic phase leads to a decrease in the permittivity and elastic compliance. The anomaly of permittivity found near T N indicates the presence of magnetoelectric interaction in the magnetically ordered phase. 相似文献
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D. Varshney R.N.P Choudhary C. Rinaldi R.S. Katiyar 《Applied Physics A: Materials Science & Processing》2007,89(3):793-798
The polycrystalline samples of Ba-modified Pb(Fe1/2Nb1/2)O3 (i.e., (Pb1-xBax)(Fe1/2Nb1/2)O3 PBFN, with x=0,0.05,0.07) were synthesized by a mechanosynthesis (i.e., high-energy ball milling) route followed by a mixed
oxide method. Structural analysis provides the information on formation of single-phase orthorhombic structure on substitution
of a small amount (x=0.07) of Ba at the Pb-site of Pb(Fe0.50Nb0.50)O3 (PFN). The ferroelectric–paraelectric phase transition in PFN was observed at 383 K, which decreases on increasing Ba-concentration
in PBFN. Detailed studies of dielectric properties of PBFW show the following: (i) diffuse phase transition, (ii) low loss
tangent, (iii) low activation energy, and (iv) low frequency dielectric dispersion. An anomaly in the ac conductivity was
found very close to phase transition temperature. The activation energy is found to decrease from 0.19 to 0.01 eV on increasing
Ba-concentration to 7% (x=0.07). Temperature field-dependent magnetization measurements of all the samples showed antiferromagnetic
transition at ∼15 K (for x=0.07). PBFN sample showed a slight increase in the coercivity (i.e., from 400 Oe (PFN) to 500 Oe
(PBFN, for x=0.07) at 2 K.
PACS 61.10.Nz; 68.37.Hk; 75.50.Ss; 75.60.Ej; 77.22.Ch; 77.22.Gm 相似文献
7.
A model Hamiltonian for B cation ordering (Sc-Nb(Ta)) in PbSc1/2Nb1/2O3 and PbSc1/2Ta1/2O3 solid solutions is constructed. The parameters of the model Hamiltonian are determined from the ab initio calculation within the ionic crystal model with allowance made for the deformability and the dipole and quadrupole polarizabilities of the ions. The temperatures of the phase transition due to the ordering of the B cations are calculated by the Monte Carlo method in the mean-field and cluster approximations. The phase transition temperatures calculated by the Monte Carlo method (1920 K for PbSc1/2Ta1/2O3 and 1810 K for PbSc1/2Nb1/2O3) are consistent with the experimental data (1770 and 1450 K, respectively). The thermodynamic properties of the cation ordering are investigated using the Monte Carlo method. 相似文献
8.
Banarji Behera Pratibindhya Nayak Ram N. P. Choudhary 《Central European Journal of Physics》2008,6(2):289-295
A polycrystalline sample of KCa2Nb5O15 with tungsten bronze structure was prepared by a mixed oxide method at high temperature. A preliminary structural analysis
of the compound showed an orthorhombic crystal structure at room temperature. Surface morphology of the compound shows a uniform
grain distribution throughout the surface of the sample. Studies of temperature variation on dielectric response at various
frequencies show that the compound has a transition temperature well above the room temperature (i.e., 105°C), which was confirmed
by the polarization measurement. Electrical properties of the material have been studied using a complex impedance spectroscopy
(CIS) technique in a wide temperature (31–500°C) and frequency (102–106 Hz) range that showed only bulk contribution and non-Debye type relaxation processes in the material. The activation energy
of the compound (calculated from both the loss and modulus spectrum) is same, and hence the relaxation process may be attributed
to the same type of charge carriers. A possible ‘hopping’ mechanism for electrical transport processes in the system is evident
from the modulus analysis. A plot of dc conductivity (bulk) with temperature variation demonstrates that the compound exhibits
Arrhenius type of electrical conductivity.
相似文献
9.
K. Yu. Gufan M. Yu. Gurevich R. V. Kolesova Yu. M. Gufan 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(8):1043-1049
A sequence of structural models of unit cells of complex oxides with perovskite-type structure has been constructed to refine the average structure of PbFe1/2Nb1/2O3 (PFN) at temperatures above the ferroelectric Curie point (T C ~ 110°C). Owing to the analysis of the probability theory considerations, each model is characterized by only two positional fitting parameters. With the use of the intensities of 95 symmetrically independent X-ray reflections from a PFN single crystal at 160°C, a model with the R factor below 3% (K = 2.44%) was chosen. The ravine method has been used to verify the existence of a single minimum for the R factor with respect to the fitting parameter. 相似文献
10.
V. I. Zinenko N. G. Zamkova E. G. Maksimov S. N. Sofronova 《Journal of Experimental and Theoretical Physics》2007,105(3):617-625
The dynamic Born charges and the frequency spectra of lattice oscillations in the crystals of ordered and disordered PbSc1/2Ta1/2O3 (PST) and PbSc1/2Nb1/2O3 (PSN) solid solutions have been calculated within the framework of the generalized Gordon-Kim model with allowance for the dipole and quadrupole polarizabilities. The phonon spectra of both compounds contain ferroelectric soft modes. The influence of various interactions on the magnitude of dynamic charges and ferroelectric instability in PSN and PST solid solutions has been studied and it is shown that both these charges and the ferroelectric instability are determined by the competition between long-range dipole-dipole interactions and short-range dipole-charge interactions, the determining role played by the interaction of Nb (Ta) cations and oxygen anions in the Nb-O (Ta-O) bond direction. 相似文献
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N. G. Zamkova S. N. Sofronova V. I. Zinenko 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(2):224-227
Ferroelectric phase transitions and thermodynamic properties of disordered PbSc1/2Ta1/2O3 and PbSc1/2Nb1/2O3 solid solutions have been investigated by the Monte Carlo method. The parameters of the effective Hamiltonian were calculated within the generalized Gordon-Kim model. The obtained values of the phase-transition temperatures and spontaneous polarization are in satisfactory agreement with the experimental data. 相似文献
12.
Dunmin Lin K.W. Kwok H.L.W. Chan 《Applied Physics A: Materials Science & Processing》2008,91(1):167-171
(K0.5Na0.5)(Nb1-xTax)O3 lead-free piezoelectric ceramics have been prepared by an ordinary sintering technique. The results of X-ray diffraction
reveal that Ta5+ diffuses into the K0.5Na0.5NbO3 lattices to form a solid solution with an orthorhombic perovskite structure. Because of the high melting temperature of KTaO3, the (K0.5Na0.5)(Nb1-xTax)O3 ceramics can be sintered at higher temperatures. The partial substitution of Ta5+ for the B-site ion Nb5+ decreases both paraelectric/cubic–ferroelectric/tetragonal and ferroelectric/tetragonal–ferroelectric/orthorhombic phase
transition temperatures, TC and TO-T. It also induces a relaxor phase transition and weakens the ferroelectricity of the ceramics. The ceramics become ‘softened’,
leading to improvements in d33, kp, kt and εr and a decease in Ec, Qm and Np. The ceramics with x=0.075–0.15 become optimum, having d33=127–151 pC/N, kp=0.43–0.44, kt=0.43–0.44, εr=541–712, tanδ=1.75–2.48% and TC=378–329 °C.
PACS 77.65.-j; 77.84.Dy; 77.84.-s 相似文献
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The polarization mode dispersion induced by an external ac electric field in PbMg1/3Nb2/3O3 single crystals is studied experimentally at frequencies of 104–107 Hz. It is established that the discovered electro-optical polarization mode dispersion (EPMD) displays anomalous properties related to the orientation of the induced dipole moments in microregions of the crystal. Analytical expressions describing the peculiarities of the physical properties of relaxors giving rise to the EPMD are obtained. 相似文献
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Malgorzata Adamczyk Lucjan Kozielski Dariusz Bochenek Daria Radoszewska Marian Pawełczyk Beata Wodecka-Duś 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(2):37
In recent years a wide range of Aurivillius layered materials have been introduced. These novel materials are produced in many various forms such as fibers, thin films as well as bulk by using a number of processing routes. As advanced materials they are they have many interesting properties which include a number of useful electrical properties related to separated grain and grain boundary conductivity, impedance, activation energies, etc. In this paper these properties are described and discussed in detail. The electrical properties of the vanadium doped BaBi2Nb2O9 ceramic was measured over a wide range of temperatures by impedance spectroscopy (IS). The separated grain activation energy, calculated from Arrhenius characteristics at temperatures between room temperature and 600 °C, was 1 eV for 0 at.% of vanadium dopant and 1.2 eV for 10 at.%, whereas the activation energies in the grain boundary region were 0.97 and 1.15 eV, respectively. The obtained results suggest the significant role of vanadium dopant, causing ordering the crystalline structure. 相似文献
15.
M. V. Gorev I. N. Flerov V. S. Bondarev Ph. Sciau 《Journal of Experimental and Theoretical Physics》2003,96(3):531-537
Heat capacity of the PbMg1/3Nb2/3O3 compound is measured using the methods of adiabatic and differential scanning calorimetry in the temperature range 80–750 K. Two blurred anomalies on the C p (T) dependence are observed in wide temperature intervals of 200–400 K and 500–700 K. The results of studies are discussed together with data on the structure and phonon spectrum in the framework of spherical random bond-random field model. 相似文献
16.
S. Wongsaenmai W. Qu S. Ananta R. Yimnirun X. Tan 《Applied Physics A: Materials Science & Processing》2007,88(4):757-761
Ferroelectric ceramics with formula Pb0.8Ba0.2[(In1/2Nb1/2)1-xTix]O3 (PBINT) (x=0.0,0.1,0.2,0.3,0.4 and 0.5) were prepared via a two-step solid state reaction method. It was found that ceramics
with compositions in the range of x=0.0∼0.3 showed a pseudo-cubic structure, whereas the ceramic with x=0.5 displayed a tetragonal
structure. All compositions showed significant frequency dispersion in their dielectric properties. The remanent polarization
Pr as well as the coercive field Ec, measured at room temperature, increases with the Ti content. The experimental results obtained in this system are summarized
into a phase diagram, with the morphotropic phase boundary (MPB) located at x=0.4. Compared with the Pb[(In1/2Nb1/2)1-xTix]O3 solid solution system, incorporating Ba in the A-site leads to a significant decrease in the dielectric maximum temperature
Tmax, a suppression of the dielectric relaxation parameter γ, and a shift of the MPB composition to a higher Ti content.
PACS 77.84.Dy; 77.80.Bh; 77.22.Ch 相似文献
17.
Weibo Zhu Zhenyuan Zhuang Zhiya Lin Yanmin Yang Yingbin Lin Zhigao Huang 《Ionics》2016,22(9):1533-1540
Layered LiNi1/3Co1/3Mn1/3O2 cathode material is synthesized via a sol-gel method and subsequently surface-modified with Eu2O3 layer by a wet chemical process. The effect of Eu2O3 coating on the electrochemical performances and thermal stability of LiNi1/3Co1/3Mn1/3O2@Eu2O3 cells is investigated systematically by the charge/discharge testing, cyclic voltammograms, AC impedance spectroscopy, and DSC measurements, respectively. In comparison, the Eu2O3-coated sample demonstrates better electrochemical performances and thermal stability than that of the pristine one. After 100 cycles at 1C, the Eu2O3-coated LiNi1/3Co1/3Mn1/3O2 cathode demonstrates stable cyclability with capacity retention of 92.9 %, which is higher than that (75.5 %) of the pristine one in voltage range 3.0–4.6 V. Analysis from the electrochemical measurements reveals that the remarkably improved performances of the surface-modified composites are mainly ascribed to the presence of Eu2O3-coating layer, which could efficiently suppress the undesirable side reaction and increasing impedance, and enhance the structural stability of active material. 相似文献
18.
A precursor of TiO2–LiCo1/3Ni1/3Mn1/3O2 was prepared by electrostatic self-assembly method. The final product was obtained by heating the precursor at 400–450 °C
for 4–6 h in air. X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and
electrochemical tests were used to examine the structural, morphology, elementary valence, and electrochemical characteristics.
XRD indicated that the TiO2-coated material can be indexed by α-NaFeO2 layered structure, which belongs to hexagonal-type space group R3m. XPS results confirmed the existence of TiO2 compound on the surface of the coated sample. The SEM image showed that the material had spherically porous morphology with
the uniform size about 6 μm. The initial charge–discharge capacity of the TiO2-coated LiCo1/3Ni1/3Mn1/3O2 material was 168.8/160.0 mAh/g. After 60 cycles, the discharge capacity of the TiO2-coated LiCo1/3Ni1/3Mn1/3O2 sample was 147.0 mAh/g, and the coulombic efficiency was 94.0%. Compared with the uncoated sample, the electrochemical performance
of TiO2-coated LiCo1/3Ni1/3Mn1/3O2 was improved. 相似文献
19.
The pure phase P2-Na2/3Ni1/3Mn2/3O2 was synthesized by a solid reaction process. The optimum calcination temperature was 850 °C. The as-prepared product delivered a capacity of 158 mAh g?1 in the voltage range of 2–4.5 V, and there was a phase transition from P2 to O2 at about 4.2 V in the charge process. The P2 phase exhibited excellent intercalation behavior of Na ions. The reversible capacity is about 88.5 mAh g?1 at 0.1 C in the voltage range of 2–4 V at room temperature. At an elevated temperature of 55 °C, it could remain as an excellent capacity retention at low current rates. The P2-Na2/3Ni1/3Mn2/3O2 is a potential cathode material for sodium-ion batteries. 相似文献
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I. P. Aleksandrova A. A. Sukhovsky Yu. N. Ivanov I. P. Raevsky 《Physics of the Solid State》2012,54(2):316-323
The local structure of the ferroelectric-relaxor PbSc1/2Nb1/2O3 in the temperature range from 550 to 220 K has been investigated using 45Sc nuclear magnetic resonance. It has been found that, in the paraelectric phase at temperatures below 550 K, the crystal
consists of regions of an ordered elpasolite structure and inclusions of the disordered tetragonal perovskite phase with displacements
along directions of the [001] type. The relative weight of the tetragonal structure in the region of the paraelectric phase
is approximately equal to 0.28. Below the temperature of the phase transition from the disordered modification to the polar
phase, the relative weight of the tetragonal phase decreases with decreasing temperature. The tetragonal structure is replaced
by the trigonal polar structure. In a wide temperature range (∼50 K), there exists a heterophase structure that is characteristic
of relaxors. Note that the correlation length of displacements in the tetragonal phase should be very small to explain the
absence of indications of the existence of this phase in the diffraction data. 相似文献