共查询到20条相似文献,搜索用时 15 毫秒
1.
N. Sawangwan J. Barrel K. MacKenzie T. Tunkasiri 《Applied Physics A: Materials Science & Processing》2008,90(4):723-727
The effect of Zr content on the crystal structure and electrical properties of barium zirconate titanate (Ba(Zr,Ti)O3) was studied by X-ray diffraction and dielectric, ferroelectric and impedance spectroscopy. An increase of Zr content into
BaTiO3 leads to a reduction in its c-parameter and an increase in its a-parameter, resulting in a change from tetragonal to cubic
symmetry of the BaTiO3 unit cell. The Curie temperatures are lowered and the relative permittivity values are decreased with increasing Zr content.
The presence of BaZrO3 secondary phases has the affect of decreasing tanδ. A higher applied electric field is required during the polarization process
because of the effect of domain-wall pinning caused by oxygen vacancies. Impedance spectroscopy studies of Ba(Ti0.95Zr0.05)O3 ceramics show a decrease in the bulk resistance with increasing temperature, indicating a typical negative temperature coefficient
of resistance.
PACS 74.62.Bf; 74.62.Yb; 77.22.Ch; 77.80.Bh; 77.84.Dy 相似文献
2.
L. S. Kamzina I. P. Raevskii S. M. Emel’yanov S. I. Raevskaya E. V. Sahkar 《Physics of the Solid State》2004,46(5):908-914
The dielectric and optical (optical transmission, small-angle light scattering, birefringence) properties of PMNT-0.2 single crystals and their variation induced by a dc electric field have been studied. The birefringence was found to increase anomalously at the transition from the rhombohedral ferroelectric to the inhomogeneous relaxor phase (the spontaneous ferroelectric transition temperature Tsp). Below Tsp, the dielectric and optical properties were observed to exhibit anomalies originating from reorientation and growth of domains in size. Unlike ferroelectric relaxors of the type of PbB′1/3B′2/3O3 and PbB′1/2B′1/2O3, in PMNT-0.2 neither induction of the ferroelectric phase by an electric field nor thermally stimulated destruction of the ferroelectric state occurs through the percolation mechanism (i.e., they are not accompanied by anomalously narrow maxima in small-angle light scattering). This is attributed to the inhomogeneous structure of the relaxor phase, as a result of which the phase transition does not take place simultaneously in various regions of the crystal. 相似文献
3.
D. Bochenek 《The European physical journal. Special topics》2008,154(1):15-18
The work shows basic features of ferromagnetic ceramics
Pb(Fe1 - xNbx)O3 with various contents of Fe/Nb (x=1/3, 1/2,
2/3). The synthesis were carried out by powders sintering and calcination whereas densification by hot uniaxial pressing and
conventional sintering methods. Optimum conditions of PFN obtention with various contents were
based on X-ray, microstructural, dielectrical and conductivity tests together with increase of iron contents in Pb(Fe1 - xNbx)O3 usage parameters of those ceramics worsen. Optimum parameters are shown by
the ceramics with contents Pb(Fe1 / 2Nb1 / 2)O3 synthetized using calcination method and densified by hot uniaxial pressing method. 相似文献
4.
Zbigniew Machnik Dariusz Bochenek Beata Wodecka-Dus Małgorzata Adamczyk Katarzyna Osińska 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(2):34
The aim of the present work is to report investigations concerning the influence of homovalent modificators on relaxor properties of PBZT 25/70/30 ceramics. The selection of the proper homovalent additive was very important. Literature reports as well as data taken from the periodic table indicated, that calcium ions substitute themselves for lead ions with high likelihood of occurrence. The investigations showed that the substitution significantly changed the microstructure of ceramics – with grains of calcium modified ceramics decreasing and density increasing. The XRD measurements indicate that the pure PBZT ceramics as well as calcium dopant were characterised by tetragonal structure with space group I4 /mmm. Addition of calcium leads to a slight decrease in the lattice constant and crystal structure. The calcium modification also changes the dielectric properties. The temperature characteristic of the dielectric constant achieved a broadened maximum at temperature Tm, which decreases with increasing Ca content. The properties typical for ferroelectric relaxors weaken with increasing calcium dopant. 相似文献
5.
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
6.
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
7.
The maximum dielectric permittivity of Ti-doped Ta2O5 ceramics may reach 450 by a laser-sintering technique. The aim of this study is to investigate the mechanisms of the dielectric
enhancement based on the unique structural and morphological properties of the laser-sintered ceramics. The reason for the
dielectric enhancement is due to the crystal structure distortion in the high-temperature phase, the oriented grain growth
taking place in a direction deviating from [001] in the laser-sintered ceramics. The concurrent nature of quenching effects,
a sharp temperature gradient and mass transfer in liquid phase originated from laser high energy irradiation with strict directivity
leads to the structural and morphological properties.
PACS 81.40.Tv; 61.80.Ba; 77.22.-d; 77.22.Ch 相似文献
8.
Ruiting Sun Xiaoli Wang Jing Shi Le Wang 《Applied Physics A: Materials Science & Processing》2011,104(1):129-133
New perovskite solid solution ceramics of (1−x)BaTiO3-xBi(Mg1/2Ti1/2)O3 ((1−x)BT-xBMT, x≤0.09) were synthesized by the solid-state reaction technique. X-ray diffraction studies have revealed a stable single perovskite
structure for all samples. Dielectric measurements were carried out at different frequencies and temperatures. The polarization
evolutions with temperatures were measured to investigate the ferroelectric properties. All the compositions show features
of ferroelectrics with diffuse phase transition, though the temperature T
m
of their dielectric constant maximum ε
m
is frequency dependent. The dielectric constant peak ε(T) of (1−x)BT-xBMT ceramics become broad with increasing BMT content. During the temperature range of ε(T) peak summit, (1−x)BT-xBMT ceramics present quasi-linear dielectric phenomenon under high electric field with very high dielectric constant. 相似文献
9.
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
10.
11.
X. W. Zhang J. B. Xia 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(3):263-268
The electronic structure, spin splitting energies, and g factors of
paramagnetic In1-xMnxAs nanowires under magnetic and electric
fields are investigated theoretically including the sp-d exchange
interaction between the carriers and the magnetic ion. We find that the
effective g factor changes dramatically with the magnetic field. The spin
splitting due to the sp-d exchange interaction counteracts the
Zeeman spin splitting. The effective g factor can be tuned to zero by the
external magnetic field. There is also spin splitting under an electric
field due to the Rashba spin-orbit coupling which is a relativistic effect.
The spin-degenerated bands split at nonzero kz (kz is the wave
vector in the wire direction), and the spin-splitting bands cross at
kz = 0, whose kz-positive part and negative part are symmetrical. A
proper magnetic field makes the kz-positive part and negative part of
the bands asymmetrical, and the bands cross at nonzero kz. In the
absence of magnetic field, the electron Rashba coefficient increases almost
linearly with the electric field, while the hole Rashba coefficient
increases at first and then decreases as the electric field increases. The
hole Rashba coefficient can be tuned to zero by the electric field. 相似文献
12.
X.T. Li P.Y. Du H. Ye C.L. Mak K.H. Wong 《Applied Physics A: Materials Science & Processing》2008,92(2):397-400
Textured LixNi2-xO (LNO) thin films have been fabricated on (001)MgO substrates by pulsed laser deposition technique. The as-deposited LNO
films shows a conductivity of 2.5×10-3 Ω m and possess a transmittance of about 35% in the visible region. Subsequent deposition of Sr0.6Ba0.4Nb2O6 (SBN60) thin film on these LNO-coated MgO substrates resulted in a textured SBN layer with a 〈001〉 orientation perpendicular
to the substrate plane. Phi scans on the (221) plane of the SBN layer indicated that the films have two in-plane orientations
with respect to the substrate. The SBN unit cells were rotated in the plane of the film by ± 8.2° as well as ± 45° with respect
to the LNO/MgO substrate. Besides the highly (00l)-orientation, the SBN films also exhibited a dense microstructure as shown
by scanning electron microscopy. The electro-optic coefficient (r33) of the SBN film was measured to be 186 pm/V. On the basis of our results, we have demonstrated that the LNO film can be
used as a buffer layer as well as a transparent bottom electrode for waveguide applications. The SBN/LNO heterostructure is
also a suitable candidate for integrated electro-optics devices.
PACS 42.79.Gn; 42.82.Et; 78.20.Ci 相似文献
13.
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
14.
We have investigated the structural and thermoelectric properties of (Sb1-xBix)2Te3 thin films on CdTe(111)B. Analysis of X-ray diffraction patterns (–2 scans and rocking curves) of the films shows that they are of high quality and that they are well aligned with their (00.1) axis normal to the substrates. Measurements of the temperature-dependent thermoelectric power, resistivity, and Hall coefficient of the films were performed with respect to the binary composition, x. For the samples in the range 0.2<x<0.3, the room-temperature thermopower values were in the range 159–184 V/K, the room-temperature carrier concentrations were 3.93–5.13×1019 cm-3, and the room-temperature mobilities were 24.6–64.0 cm2V-1s-1. PACS 72.20.Pa; 72.80.Jc; 73.6l.Le 相似文献
15.
V. B. Shirokov V. V. Kalinchuk R. A. Shakhovoi Yu. I. Yuzyuk 《Physics of the Solid State》2016,58(10):2035-2039
The behavior of material constants in ferroelectric Ba0.8Sr0.2TiO3 thin films is studied depending on the misfit strain at room temperature in the context of nonlinear thermodynamic potential of the phenomenological theory. Some constants are found to undergo drastic changes with the alternating strain at the interfaces. The gathered results allow one to evaluate the material constants for a specific film and to outline the direction in searching the ways to synthesize films with the needed properties. 相似文献
16.
In the paper the influence of mechanical activation of the powder on the final dielectric properties lead-free Ba(Fe1/2Nb1/2)O3 (BFN) ceramic was examined. The BFN ceramics were obtained by 3-steps route. Firstly, the substrates were pre-homogenized in a planetary ball mill. Than, the powder was activated in vibratory mill (the shaker type SPEX 8000 Mixer Mill) for different duration between 25 h and 100 h. The influence of the milling time on the BFN powder was monitored by X-ray diffraction. The diffraction data confirmed that the milling process of the starting components is accompanied by partial synthesis of the BFN materials. The longer of the high-energy milling duration the powders results in increasing the amount of amorphous/nanocrystalline content. The mechanically activated materials were sintered in order to obtain the ceramic samples. During this temperature treatment the final crystallisation of the powder appeared what was confirmed by XRD studies. The performed dielectric measurements have revealed the reduction of the dielectric loss of the BFN ceramics compared to materials obtained by classic methods. 相似文献
17.
H. Tian Z. Zhou D. Gong H. Wang D. Liu Y. Jiang 《Applied physics. B, Lasers and optics》2008,91(1):75-78
We report the successful growth of an electroholographic crystal, potassium sodium tantalate niobate (KNTN), by a top-seeded
solution growth method. Both blue and colorless crystals were obtained. The structure, optical absorption, and refractive
dispersion properties of the as-grown crystals have been investigated. Furthermore, the Kerr coefficients R11 and R12 of paraelectric K0.95Na0.05Ta0.61Nb0.39O3 single crystal were determined by using an automated scanning Mach–Zehnder interferometer. The crystal has large Kerr coefficients
with R11= 2.8×10-16 m2/V2 and R12= -0.3×10-16 m2/V2 at the wavelength of 632.8 nm near its cubic–tetragonal phase boundary.
PACS 81.10.Dn; 42.70.Nq 相似文献
18.
This is an IR spectroscopic study of the interaction of CO with In2O3 and the nanocomposite In2O3-Au. A mechanism for low-temperature detection of CO on nanocomposite In2O3-Au can be determined from these data. This process includes catalytic oxidation of CO through formation of intermediate complexes
involving hydroxyl groups of In2O3. 相似文献
19.
V. Yu. Topolov 《Physics of the Solid State》2003,45(7):1295-1297
A new model of the elastic matching of phases is proposed, and heterophase structures near the morphotropic phase boundary in 0.10PbTiO3-0.90Pb(Zn1/3Nb2/3)O3 crystals are studied. Unique behavior of the unit cell parameters is found to favor the elastic matching of the ferroelectric tetragonal and orthorhombic phases under the conditions of complete or partial relaxation of internal mechanical stresses at a volume concentration ratio of these phases of about 20/80% and temperatures of T=20–300 K. Interrelations between the volume concentrations of different domain (twin) types and of the coexisting phases are analyzed. 相似文献
20.
W. Liu Y. Sun W. Li C.-J. Li F.-Y. Li J.-G. Tian 《Applied Physics A: Materials Science & Processing》2007,88(4):653-656
The properties of Cu(In1-xGax)Se2 (CIGS) thin films obtained by selenization of the precursors with different surface layers have been studied, and photovoltaic
devices based on the absorbers were measured and analyzed. The devices constructed by the absorbers obtained by selenization
of the precursors with CuGa-rich surface layers are improved, compared with those with In-rich surface layers. Through XRD,
SEM, SIMS, illuminated J–V, QE and Raman spectra measurements, it was found that the increased Ga contents within the surface
region of films and the graded Ga distribution can be realized in the selenized thin films fabricated by the precursors with
the CuGa-rich surface layer. Consequently, the performances of the photovoltaic devices based on these thin films are further
improved.
PACS 61.72.Ss; 87.64.Jt; 68.60.Bs; 81.15.Cd; 84.60.Jt 相似文献