共查询到20条相似文献,搜索用时 15 毫秒
1.
M. D. Durruthy-Rodríguez J. Costa-Marrero M. Hernández-Garcia F. Calderón-Pi?ar Célia Malfatti J. M. Yá?ez-Limón 《Applied Physics A: Materials Science & Processing》2011,103(2):467-476
In this work, visible photoluminescence was observed at room temperature in a sintered Pb(Zr1-xTix)1-y NbyO3\mathrm{Pb}(\mathrm{Zr}_{1-x}\mathrm{Ti}_{x})_{1-y} \mathrm{Nb}_{y}\mathrm{O}_{3} perovskite-type structure system, doped with Nb using the next excitation bands 325, 373 and 457 nm. The intensity and energy
of such emissions have been studied by changing the Nb concentration (0<y<0.01) and the Ti content (x), with x=0.20,0.40,0.53,0.60 and 0.80, on both sides of the morphotropic phase boundary (MPB) zone. The principal bands become visible
at energies of 1.73, 2.56 and 3.35 eV. The results reveal the role of the Nb5+ ion substitutions by Zr4+ or Ti4+ ions and the symmetry presented in the rhombohedral or tetragonal side of the MPB. Raman spectra which are similar for compositions:
20/80, 40/60 and 53/47 (tetragonal phases) show nine bands, centered around 137, 194, 269, 331, 434, 550, 612, 712 and 750
cm−1. The spectra for samples 60/40 and 80/20, rhombohedral phase, show significant differences, only six bands appear, centered
around 124, 209, 234, 330, 549 and 682 cm−1. In addition, optical absorption spectroscopy, structural and micro-structural measurements were carried out by using Uv-vis
spectroscopy, X-ray diffraction and scanning electron microscopy techniques, respectively. The experimental results of band
gap energy, e.g., in our samples are in accordance with the findings by J. Baedi et al. in the calculations of band structure,
energy gap and density of states for different phases of Pb(Zr1−x
Ti
x
)O3 using density functional theory (DFT). 相似文献
2.
M. V. Gorev I. N. Flerov Ph. Sciau S. Guillemet-Fritsch 《Physics of the Solid State》2009,51(4):790-796
Deformation and the thermal expansion coefficient of ceramic samples of (Ba1 − x
La
x
)Ti1 − x/4O3 solid solutions (x = 0, 0.026, 0.036, 0.054) were studied in the temperature range 120–700 K. Based on an analysis of the data obtained, the
temperature-composition phase diagram is refined, and the temperature dependence of the polarization is calculated. The results
are discussed in combination with the dielectric measurement data.
Original Russian Text ? M.V. Gorev, I.N. Flerov, Ph. Sciau, S. Guillemet-Fritsch, 2009, published in Fizika Tverdogo Tela,
2009, Vol. 51, No. 4, pp. 746–752. 相似文献
3.
4.
Zeyang Zhang Xiangxuan Liu Xuanjun Wang Youpeng Wu Yuan Liu 《Journal of magnetism and magnetic materials》2012
Shell-core Fe–Sr0.8La0.2Fe11.8Co0.2O19 composites are prepared by chemical vapor deposition (CVD) for use as microwave absorbing materials. Scanning electron microscopy and X-ray diffraction analyses show that the CVD method yields Sr0.8La0.2Fe11.8Co0.2O19 powders with a uniform coating of Fe. Compared with Sr0.8La0.2Fe11.8Co0.2O19, Fe–Sr0.8La0.2Fe11.8Co0.2O19 composites have higher electrical conductivity, permittivity, and dielectric loss, which gradually increase with increasing Fe content. When Sr0.8La0.2Fe11.8Co0.2O19/Fe=7:3, a reflection loss (RL) exceeding −10 dB is obtained in the frequency range of 10–14 GHz at a coating thickness of 2.0 mm. A minimum RL of −30 dB was found at 8.0 GHz, corresponding to a matching thickness of 2.8 mm. 相似文献
5.
I. O. Troyanchuk D. V. Karpinsky V. M. Dobryanski? A. N. Chobot G. M. Chobot A. P. Sazonov 《Journal of Experimental and Theoretical Physics》2009,108(3):428-434
The Sr0.78Y0.22Co1 − x
Fe
x
O3 − γ cobaltite system is studied by neutron and X-ray diffraction and by measuring the magnetization and elastic properties. The
crystal structure of the composition with x = 0 is described in terms of the monoclinic space group A2/m with the unit cell 2
a
p
× 4a
p
× 2
a
p
, and the crystal structure of the composition with x = 0.12 is orthorhombic (space group Imma). The crystal structure of these compounds is characterized by alternating CoO6 and CoO4.5 layers. The magnetic structure is a G-type antiferromagnetic structure. The magnetic moments in the CoO6 layers are significantly higher than those in the CoO4.5 layers. In the compound with x = 0, magnetic measurements reveal a small ferromagnetic component (0.2 μB/Co) below T
N ≈ 350 K. Near T
N, a phase transformation occurs and lowers the crystallographic symmetry. Doping with iron ions suppresses the ferromagnetic
component and sharply increases the average magnetic moments in both layers. The spontaneous magnetization is assumed to result
from noncollinear magnetic moments, which can be caused by the competition of exchange interactions of different signs and
magnetic anisotropy. The compounds with x = 0.5 and 1.0 are cubic (space group Pm3m) and are characterized by a G-type collinear antiferromagnetic structure.
Original Russian Text ? I.O. Troyanchuk, D.V. Karpinsky, V.M. Dobryanskiĭ, A.N. Chobot, G.M. Chobot, A.P. Sazonov, 2009, published
in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2009, Vol. 135, No. 3, pp. 490–497. 相似文献
6.
Fine and uniform La0.6Sr0.4Co0.2Fe0.8O3−δ
powder was synthesized by a glycine–nitrate combustion process. La0.6Sr0.4Co0.2Fe0.8O3−δ
electrodes were prepared on dense Ce0.8Sm0.2O2−δ
electrolyte substrates using a spin-coating technique by sintering at 900–1,000 °C. The electrode properties of La0.6Sr0.4Co0.2Fe0.8O3−δ
were investigated by electrochemical impedance spectroscopy and chronopotentiometry techniques with respect to preparation
conditions and the resulting microstructures. The results indicate a significant effect of the microstructure on the electrode
processes and polarization characteristics. The oxygen adsorption and dissociation process acted as a larger contribution
to the overall electrode polarization R
p in magnitude compared with the charge transfer process due to relatively low porosity levels of the electrodes. It was detected
that the grain size of the electrodes exhibited a crucial role on the electrocatalytic reactivity. At 800 °C, the electrode
sintered at 950 °C attained a polarization resistance of 0.18 Ω cm2, an overpotential of 27 mV at a current density of 200 mA cm−2, and an exchange current density of 308 mA cm−2. 相似文献
7.
E. I. Lakhno E. I. Burmakin I. V. Korzun G. Sh. Shekhtman 《Physics of the Solid State》2012,54(3):504-507
The rubidium monoferrite RbFeO2-based solid solutions with the composition Rb2 − 2x
Fe2 − x
P
x
O4 have been synthesized, and their crystal structure and the temperature and concentration dependences of the total and electron
conductivities have been studied. The introduction of P5+ ions has been found to sharply decrease the electron conductivity that prevails in pure rubidium monoferrite and, at the
same time, to increase the ionic conductivity. The latter becomes dominant as the phosphorus concentration increases. The
maximum rubidium-cation conductivity of the materials under study is ∼3 × 10−2 S/cm at 300°C and ∼3 × 10−1 S/cm at 700°C. The results have been compared with the previously obtained data for similar solid solutions based on rubidium
monogallate and monoaluminate. 相似文献
8.
I. Ruiz de Larramendi R. López-Antón J. I. Ruiz de Larramendi T. Rojo 《Applied Physics A: Materials Science & Processing》2008,93(3):655-661
Polycrystalline samples of Pr1−x
Sr
x
Fe0.8Co0.2 O3−δ
(x=0.1, 0.2, 0.3) (PSFC) were prepared by the combustion synthesis route at 1200°C. The structure of the polycrystalline powders
was analysed with X-ray powder diffraction data. The X-ray diffraction (XRD) patterns were indexed as the orthoferrite similar
to that of PrFeO3 having a single-phase orthorhombic perovskite structure (Pbnm). Pr1−x
Sr
x
Fe0.8Co0.2O3−δ
(x=0.1, 0.2, 0.3) films have been deposited on yttria-stabilized zirconia (YSZ) single-crystal substrates at 700°C by pulsed
laser deposition (PLD) for application to thin film solid oxide fuel cell cathodes. The structure of the films was analysed
by XRD, scanning electron microscopy (SEM) and atomic force microscopy (AFM). All films are polycrystalline with a marked
texture and present pyramidal grains in the surface with different size distributions. Electrochemical impedance spectroscopy
(EIS) measurements of PSFC/YSZ single crystal/PSFC test cells were conducted. The Pr0.7Sr0.3Fe0.8Co0.2O3−δ
film at 850°C presents a lower area specific resistance (ASR) value, 1.65 Ω cm2, followed by the Pr0.8Sr0.2Fe0.8Co0.2O3−δ
(2.29 Ω cm2 at 850°C) and the Pr0.9Sr0.1Fe0.8Co0.2O3−δ
films (5.45 Ω cm2 at 850°C). 相似文献
9.
V. S. Rusakov N. I. Chistyakova I. A. Burkovsky A. M. Gapochka T. L. Evstigneeva 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(3):389-393
A M?ssbauer study of the structural and charge states of 57Fe and 119Sn atoms in the compounds of Cu3 −x
Fe
x
SnS4 and Cu2Fe1 − x
Zn
x
SnS4 systems was performed. It was shown that the iron atoms in the compounds of both systems were in the divalent and trivalent
states occupying the tetrahedral positions of the structure. The character of the changes of the degree of covalency of the
Fe2+-S, Fe3+-S and Sn4+-S bonds during the isomorphic substitution in the systems was established. 相似文献
10.
We study the effect of sublattice doping of cobalt on a crystal structure and oxygen nonstoichiometry of cobaltites GdBaCo2 − xFe
x
O6 − δ (x = 0 − 0.6), which have considerable oxygen nonstoichiometry and show high values of oxygen-ionic and electronic conduction.
These properties can be varied easily by a doping of oxide. We obtained the temperature dependences of the parameters of an
elementary lattice in the range 25–800°C. 相似文献
11.
A. A. Demidov I. A. Gudim E. V. Eremin 《Journal of Experimental and Theoretical Physics》2012,114(2):259-272
The magnetic properties of ferroborate single crystals with substituted compositions Nd1 − x
Dy
x
Fe3(BO3)4 (x = 0.15, 0.25) with competing exchange Nd-Fe and Dy-Fe interactions are investigated. For each composition, we observed a
spontaneous spin-reorientation transition from the easy-axis to the easy-plane state and step anomalies on the magnetization
curves for the spin-flop transition induced by a magnetic field B | c. The measured parameters and effects are interpreted using a unified theoretical approach based on the molecular field approximation
and on calculations performed in the crystal-field model for the rare-earth ion. The experimental temperature dependences
of the initial magnetic susceptibility from T = 2 K to T = 300 K, anomalies on the magnetization curves for B | c in fields up to 1.8 T, and their evolution with temperature, as well as temperature and field dependences of magnetization
in fields up to 9 T are described. In the interpretation of experimental data, the crystal-field parameters in trigonal symmetry
for the rare-earth subsystem are determined, as well as the parameters of Nd-Fe and Dy-Fe exchange interactions. 相似文献
12.
I. O. Troyanchuk A. N. Chobot N. V. Tereshko D. V. Karpinskii V. Efimov V. Sikolenko P. Henry 《Journal of Experimental and Theoretical Physics》2011,112(5):837-847
The structural, magnetic, and magnetotransport properties of Pr0.5Sr0.5Co1 − x
Mn
x
O3 (x < 0.65) perovskites are studied by magnetization and electrical conductivity measurements in magnetic fields up to 14 T and
by neutron diffraction. In the manganese concentration range x < 0.5 and T = 300 K, the crystal structure is described by monoclinic space group I2/a; at x > 0.5, it is described by orthorhombic space group Imma. When the temperature decreases, a structural transformation without changing the symmetry takes place in all compounds.
This transformation is caused by an active role of the inner shells of the praseodymium ion in chemical bond formation. The
substitution of manganese for cobalt breaks a long-range ferromagnetic order near x ≈ 0.25, and a metal-dielectric transition occurs at x ≈ 0.15. The negative magnetoresistance is found to be maximal near a critical manganese concentration, where a long-range
magnetic order is broken; it reaches 95% in a field of 14 T at T = 10 K for x = 0.2. An unusual dielectric magnetic state with a small spontaneous magnetic moment and a sharp transition into a paramagnetic
state at T > 200 K is revealed in the concentration range 0.30 ≤ x ≤ 0.65 in spite of the absence of coherent magnetic neutron scattering. A model is proposed to explain the behavior of the
magnetic properties in this phase. 相似文献
13.
14.
V. S. Zakhvalinski? R. Laiho T. S. Orlova A. V. Khokhulin 《Physics of the Solid State》2008,50(1):63-70
The temperature dependences of the magnetic susceptibility χ(T) and the electrical resistivity ρ(T) of ceramic samples of La1 − x
Ca
x
MnO3 with x = 0.67 (LCMO) and La1 − x
Ca
x
Mn1 − y
Fe
y
O3 with x = 0.67 and y = 0.05 (LCMFO) are investigated in magnetic fields B = 50–105 G and the temperature range T = 4.2–400 K. Both samples undergo a transition from the paramagnetic state to a state with charge (orbital) ordering (CO)
at temperatures T
CO ≈ 272 K for LCMO and T
CO ≈ 222 K for LCMFO. The behavior of the paramagnetic phase in the temperature range 320–400 K for LCMO and 260–400 K for LCMFO
is described by the Curie-Weiss law with effective Bohr magneton numbers p
eff = 4.83 μB (LCMO) and 4.77 μB (LCMFO), respectively. The disagreement between the observed positive Weiss temperatures (θ ≈ 175 K (LCMO) and θ ≈ 134 K
(LCMFO)) and negative Weiss temperatures required for the antiferromagnetic ground state can be explained by the phase separation
and transition to the charge-ordered state. The magnetic irreversibility for T < T
CO is accounted for by the existence of a mixture of the ferromagnetic and antiferromagnetic phases, as well as the cluster
glass phase. At low temperatures, doping with iron enhances the frustration of the system, which manifests itself in a more
regular behavior of the decay rate of the remanent magnetization with time. The temperature dependence of the electrical resistivity
in the range of the charge-ordered phase conforms to the variable-range hopping model. The behavior of the electrical resistivity
is governed by the complex structure of the density of localized states near the Fermi level, which includes a soft Coulomb
gap Δ = 0.464 eV for LCMO and 0.446 eV for LCMFO. It is established that the ratio between the localization radii of charge
carriers a for LCMFO and a
und for LCMO is a/a
und = 0.88.
Original Russian Text ? V.S. Zakhvalinskiĭ, R. Laiho, T.S. Orlova, A.V. Khokhulin, 2008, published in Fizika Tverdogo Tela,
2008, Vol. 50, No. 1, pp. 61–68. 相似文献
15.
A. K. Zvezdin A. M. Kadomtseva Yu. F. Popov G. P. Vorob’ev A. P. Pyatakov V. Yu. Ivanov A. M. Kuz’menko A. A. Mukhin L. N. Bezmaternykh I. A. Gudim 《Journal of Experimental and Theoretical Physics》2009,109(1):68-73
Magnetic and magnetoelectric properties of ferroborate single crystals with complex composition (Tb1 − x
Er
x
Fe3(BO3)4, x = 0, 0.75) and with competing exchange Tb-Fe and Er-Fe interactions are investigated. Jumps in electric polarization, magnetostriction,
and magnetization are observed as a result of spin-flop transitions, as well as a considerable decrease in the critical field
upon an increase in the Er concentration, in a field H
c
parallel to the c axis. The observed behavior of phase-transition fields is analyzed and explained using a simple model taking into account
anisotropy in g factors and exchange splitting of funda-mental doublets of the easy-axis Tb3+ ion and easy-plane Er3+ ion. It is established that magnetoelectric and magnetostriction anomalies under spin-flop transitions are mainly controlled
by the Tb subsystem. The Tb subsystem makes a nonmonotonic contribution ΔP
a
(H
a
, T) to polarization along the a axis: the value of ΔP
a
reverses its sign and increases with temperature due to the contribution from the excited states of the Tb3+ ion.
Original Russian Text ? A.K. Zvezdin, A.M. Kadomtseva, Yu.F. Popov, G.P. Vorob’ev, A.P. Pyatakov, V.Yu. Ivanov, A.M. Kuz’menko,
A.A. Mukhin, L.N. Bezmaternykh, I.A. Gudim, 2009, published in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2009, Vol.
136, No. 1, pp. 80–86. 相似文献
16.
用溶胶-凝胶法制备了Fe掺杂BaTiO3粉体,在1350℃下烧结成圆片状多晶样品,并与Tb1-xDyxFe2-y胶合成磁电(ME)双层膜或三层膜.实验分析表明Fe:BaTiO3依然是四方相钙钛矿结构,但是居里温度及相变潜热均略低于纯净BaTiO3.研究了Tb1-xDyxFe2-y-Fe∶BaTiO3双层膜和Tb1-xDyxFe2-y-Fe∶BaTiO3-Tb1-xDyxFe2-y三层膜的ME效应.在2.8×104A/m的磁场下,两者的横向ME电压系数均达其峰值,分别为6.225和26.25mV·(A·m-1)-1·cm-1.并且,用掺杂BaTiO3制备的双层膜和三层膜的横向ME电压系数均为相同条件下用纯净BaTiO3制备的双层膜和三层膜的横向ME电压系数的1.5倍.另外由于不含铅,锆等有害物质,符合环保要求,因此采用掺杂BaTiO3制备的磁电效应器件具有深入研究和应用价值. 相似文献
17.
Guo-Yu Lan Yang-Wei Lin Zong-Hong Lin Huan-Tsung Chang 《Journal of nanoparticle research》2010,12(4):1377-1388
This article describes the synthesis of highly water-soluble Zn
x
Hg1−x
Se
y
S1−y
quantum dots (QDs) in aqueous solution through a simple photo-assisted reaction between ZnSe QDs and mercury(I) nitrate dihydrate
[Hg2(NO3)2·2H2O]. In order to deduce the optimal synthesis conditions, we varied several parameters, including the concentrations of mercaptosuccinic
acid (MSA) and Hg2(NO3)2·2H2O, the illumination time, and the reaction temperature. When irradiated at temperatures below 80 °C, the ZnSe QDs reacted
with the S2− ions formed rapidly from MSA and the Hg2+ ions formed from Hg2
2+ ions to form Zn
x
Hg1−x
Se
y
S1−y
QDs through a process of photo-etching and surface combination. Under different conditions, we prepared a series of Zn
x
Hg1−x
Se
y
S1−y
QDs that emit fluorescence at the maximum wavelengths ranging from 405 to 760 nm. Inductively coupled plasma-mass spectrometry
and transmission electron microscopy/energy dispersive spectrometry revealed that the content of Hg in the Zn
x
Hg1−x
Se
y
S1−y
QDs was greater when the synthesis was conducted at higher temperature. The Zn0.88Hg0.12Se0.44S0.56 QDs exhibit improved photostability than crude ZnSe QDs and possess long lifetimes (τ1 ~ 38 ns and τ2 ~ 158 ns). 相似文献
18.
Jie Song Bing-Lin Hong Jun Zheng Pei Lin Ming-Sen Zheng Qi-Hui Wu Quan-Feng Dong Shi-Gang Sun 《Applied Physics A: Materials Science & Processing》2010,98(2):455-460
Ti-substituted LiMn2O4 (LiMn2−x
Ti
x
O4, x=0, 0.15, 0.30, 0.45, 0.60, and 0.75) has been synthesized using solid-state reactions. Their crystal and electronic structures
were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ultraviolet photoelectron spectroscopy
(UPS). XRD data suggested that the lattice parameters of LiMn2−x
Ti
x
O4 increase due to the replacement of Mn by Ti ions. XPS results indicated that the substituted Ti ions were in +4 oxidation
state; consequently, the normal oxidation state of Mn ions has been detected by measuring the binding energy splitting of
Mn 3s states, which decreases with the content of substituted Ti. The valence band spectra suggested that the intensity of
e
g
level of Mn 3d orbitals increased due to the increase of the Mn3+/Mn4+ ratio. 相似文献
19.
I. B. Krynetsky A. I. Golovashkin A. P. Rusakov V. P. Martovitsky S. Yu. Gavrilkin V. I. Kovalenko N. P. Shabanova 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(8):1115-1117
Abnormal negative thermal expansion of single crystals of high-temperature Bi2Sr2 − x
La
x
CuO6 + · superconductor in the dielectric phase (x ≥ 0.8) was detected at low temperatures. It was established that material shrinkage upon heating occurs at higher temperatures
than in superconducting compositions. The anisotropic and nonmonotonous effect of a magnetic field of 3–6 T on the coefficient
of thermal expansion was revealed. We attribute these abnormalities to the existence of superstructure charge ordering in
the oxygen sublattice. 相似文献
20.
A. V. Savinkov A. V. Dooglav H. Alloul P. Mendels J. Bobroff G. Collin N. Blanchard 《JETP Letters》2010,91(2):83-90
Incidence of doped holes in the CuO2 plane on the AF state was studied by Cu(1) nuclear quadrupole resonance (NQR) in slightly doped YBa2(Cu1 − z
Li
z
)3O6 + x
compounds. Inhomogeneous distribution of doped holes in the plane was detected in the low temperature measurements of transverse
(1/T
2) and longitudinal (1/T
1) relaxation rates. We establish that at lower T the holes motion slows down and we estimate that the holes localize finally in restricted regions (∼3 lattice constants)
in the Coulomb potential of the Li+ ions. Also we compared the hole behavior in slightly doped YBa2(Cu1 − z
Li
z
)3O6 + x
samples with that in slightly doped Y1 − y
Ca
y
Ba2Cu3O6. A stronger trapping potential of the in-plane Li+ impurities was concluded as compared to slightly doped Y1 − y
Ca
y
Ba2Cu3O6 compound with out-of-plane Ca2+ impurities. 相似文献