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1.
The absorption spectra of Y3Ga5O12:(Fe3+), Y3Ga5O12:(Bi3+) and Y3Ga5O12:(Bi3+, Fe3+) are presented to 40,000 cm-1. Assignments are discussed and the transitions analysed in terms of their involvement in the large Faraday rotation observed in bismuth substituted iron garnets. 相似文献
2.
The Bi, Tb and Yb partially substituted iron garnet bulk single crystals of Tb3−x−yYbyBixFe5O12 were grown by using Bi2O3/B2O3 as flux and accelerated crucible rotation technique for single-crystal growth. Faraday rotation (FR) spectra showed that the specific FR of the (Tb0.91Yb1.38Bi0.71)Fe5O12 crystal under magnetic field at saturation was measured to be about −1617°/cm at λ=1.55 μm, Faraday rotation wavelength coefficient (FWC, 0.009%/nm) in the wavelength range of 1.50–1.62 μm and Faraday rotation temperature coefficient (FTC, 3.92×10−5/K) at λ=1.55 μm were even smaller than that of YIG. It is proven that through combining two types of Bi-substituted rare-earth iron garnets with opposite FWC and FTC signs, the compound rare-earth iron garnets with low FWC and FTC may be obtained due to the compensation effect. The saturation magnetization of (Tb0.91Yb1.38Bi0.71) Fe5O12 crystal is 0.48×106 A/M and is also much smaller than that of YIG. We have found empirically that there is a simple relationship between the FR θf(x) and Bi content x for Tb3−x−yYbyBixFe5O12, which is given by θf(x)=(−2759x+400)°/cm. 相似文献
3.
S. Q. Bai X. Y. Huang L. D. Chen W. Zhang X. Y. Zhao Y. F. Zhou 《Applied Physics A: Materials Science & Processing》2010,100(4):1109-1114
Alkaline-earth (AE) and rare-earth (RE) atoms are usually used as void fillers in the caged compound CoSb3 to improve the thermoelectric performance of the filled system. Polycrystalline single-filled Sr0.21Co4Sb12, double-filled Sr
x
Yb
y
Co4Sb12, and Sr
x
Ba
y
Co4Sb12 skutterudites have been synthesized. Rietveld structure refinement confirms that both Sr and Yb occupy the Sb-icosaedron
voids in skutterudite frame work. In this paper, we report the high-temperature thermoelectric properties including electrical
conductivity, Seebeck coefficient, and thermal conductivity. Double filling of the Sr–Yb combinations shows a stronger suppression
on lattice thermal conductivity than that of Sr–Ba combination. Furthermore, the double-filled Sr
x
Yb
y
Co4Sb12 skutterudites exhibit a much higher power factor than the Sr-filled system. The maximum power factor for Sr0.22Yb0.03Co4Sb12.12 reaches 41 μW cm−1 K−2 at room temperature and 57.5 μW cm−1 K−2 at 850 K, respectively. The enhanced thermoelectric figures of merit are 1.32 for Sr
x
Yb
y
Co4Sb12 and 1.22 for Sr
x
Ba
y
Co4Sb12 at 850 K, respectively. 相似文献
4.
E. D. Politova E. A. Fortalnova G. M. Kaleva M. G. Safronenko N. U. Venskovskii 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(8):1069-1072
Ceramic solid solutions (Bi1 − y
La
y
)4(V1 − x
Me
x
)2O11 − z
(x, y < 0.2: Me = Zr, Ga, Fe, Cu) were prepared by solid-state reaction. It was shown that the annealing (973 K, reducing atmosphere H2/Ar (20/80)) of the samples whose compositions belong to the stability domains of α, β, and γ′ polymorphs increases their
electronic conductivity by six orders of magnitude. The samples with low concentrations of dopant cations exhibited good compositional
stability and a reversible change in their structure parameters. At the same time, the solid solutions with a high concentration
of lanthanum cations and/or copper cations (y, x ∼ 0.1) underwent partial decomposition. 相似文献
5.
Thermal expansion measurements have been carried out on Fe substituted superconducting compounds Y1Ba2(Cu1−x
Fe
x
)3O
y
(0<x<4%) using a high resolution dilatometer employing the three terminal capacitance technique. The experimental set up is sensitive
enough to detect changes in α of less than 10−8K−1. Results show that the jump Δα in the coefficient of linear thermal expansion at the superconducting transition temperature,T
c, increases almost linearly with Fe concentration. The normal state thermal expansion coefficient α first decreases, attains
a minimum value aroundx=1% and then increases for higher Fe concentrations. The oxygen content per unit formula is almost constant up tox=1% and then increases rapidly withx. It has also been observed that the anomalous behaviour of α around 260 K observed by Meingastet al [22] for Fe concentrationx=5% is due to inadequate annealing of the sample. 相似文献
6.
The crystal structure and magnetic properties of Bi1 − x
A
x
FeO3 − x/2 (A = Ca, Sr, Pb, Ba), Bi1 − x
A
x
(Fe1 − x
Ti
x
)O3, and Bi1 − x
A
x
(Fe1 − x/2Nb
x/2)O3 solid solutions have been studied. It is shown that the homogeneous polar weak ferromagnetic state occurs in the vicinity
of a morphotropic phase boundary in the systems where dopant ions lead to the reduction of the unit cell volume in the polar
phase. In the case of A = Ca, the non-polar phase also exhibits weak ferromagnetism and the spontaneous magnetizations in
the polar and nonpolar phases differ only slightly. 相似文献
7.
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
8.
Recently, we have demonstrated the successful synthesis of Fe
x
Co1−x
/Co
y
Fe3−y
O4 nanocomposites with various alkaline solutions by using surfactants-assisted-hydrothermal (SAH) process. In this article,
the synthesis of Fe
x
Co1−x
/CoyFe3−y
O4 nanocomposites with their sizes varying between 20 nm and 2 μm was reported. X-ray powder diffraction (XRD) analyses showed
that the surfactants, pH, precipitator, and temperature of the system play important roles in the nucleation and growth processes.
The magnetic properties tested by vibrating sample magnetometer (VSM) at room temperature exhibit ferromagnetic behavior of
the nanocomposites. These Fe
x
Co1−x
/Co
y
Fe3−y
O4 nanocomposites may have a potential application as magnetic carriers for drug targeting because of their excellent soft-magnetic
properties. 相似文献
9.
Lead-free (Bi0.98−x
La0.02Na1−x
)0.5Ba
x
TiO3 ceramics have been prepared by an ordinary sintering technique and their structure, ferroelectric and piezoelectric properties
have been studied. The results of X-ray diffraction show that La2+ and Ba2+ diffuse into the Bi0.5Na0.5TiO3 lattices to form a new solid solution with a pure perovskite structure, and a morphotropic phase boundary (MPB) exists at
0.04<x<0.10. Compared with pure Bi0.5Na0.5TiO3 ceramics, the (Bi0.98−x
La0.02Na1−x
)0.5Ba
x
TiO3 ceramics possess much smaller coercive field E
c and larger remanent polarization P
r. Because of the low E
c (3.38 kV/mm), large P
r (46.2 μC/cm2) and the formation of the MPB of rhombohedral and tetragonal phases, the piezoelectric properties of the ceramics are significantly
enhanced at x=0.06: d
33=181 pC/N and k
p=36.3%. The depolarization temperature T
d reaches a minimum value near the MPB. The ceramics exhibit relaxor characteristic, which is probably a result from the cation
disordering in the 12-fold coordination sites. The temperature dependences of the ferroelectric and dielectric properties
suggest that the ceramics may contain both polar and non-polar regions at the temperatures above T
d. 相似文献
10.
A series of (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+ (x=0.0–0.97, y=0.03) phosphors were synthesized by high-temperature solid-state reaction. The XRD patterns confirm the formation of a solid
solution of (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+. An intense tunable green light is observed with the increasing ratio of Sr/Ca. With an increase in x, the excitation and emission spectra show a redshift and blueshift, respectively, due to large centroid shift and small Stokes
shift. The temperature dependent luminescence is also investigated in the temperature range of 77–450 K. The Huang–Rhys factor
and the thermal-quenching temperature are determined. Intense green LEDs were successfully fabricated based on the (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+ phosphor and near-ultraviolet (∼395 nm) GaN/blue (460 nm) InGaN chips. All the results indicate that the solid solution (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+ is a promising phosphor applicable to near-UV and blue LEDs for solid-state lighting. 相似文献
11.
The formation of InAs1−x−y
SbxBiy/InSb and InAs1−x−y
SbxBiy/InSbyBiy strained-layer heterostructures by “capillary” LPE is simulated. The laws governing the dependence of the gap width E
g
and the thickness d of the epilayers on the conditions of the process are revealed. It is shown that because of the sharp increase in the rate
of epitaxial deposition as the LPE temperature is raised, the successful growth of epilayers of subcritical thickness is possible
only up to T<550 K. The influence of the rate of laminar flow of the liquid in the growth channel in a relaxation regime and in a continuous
pumping regime on the uniformity of the distribution of E
g
and d in the epitaxial heterostructures is analyzed. Effective combinations of parameters for carrying out the process, which ensure
the achievement of E
g
≈0.1 eV (77 K) in the active layers with variable-band-gap layers of minimal thickness, are established.
Zh. Tekh. Fiz. 67, 50–56 (July 1997) 相似文献
12.
S. V. Grigoriev V. A. Dyadkin S. V. Maleyev D. Menzel J. Schoenes D. Lamago E. V. Moskvin H. Eckerlebe 《Physics of the Solid State》2010,52(5):907-913
Two systems of noncentrosymmetric cubic helical magnets Mn1 − y
Fe
y
Si (y = 0.06, 0.08, 0.10) and Fe1 − x
Co
x
Si (x = 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.50) have been compared. The concentration dependences of the critical temperature
and magnetic field have been obtained using small-angle polarized-neutron scattering and analyzed in the framework of the
Bak-Jensen model. It has been established that, among the two interactions that play the main role in these systems, i.e.,
the isotropic symmetric ferromagnetic exchange and the Dzyaloshinskii-Moriya isotropic antisymmetric interaction, the former
interaction determines the critical temperature in the Mn1 − y
Fe
y
Si system and the latter interaction determines this temperature in the Fe1 − x
Co
x
Si system. 相似文献
13.
Dunmin Lin Qiaoji Zheng Chenggang Xu K. W. Kwok 《Applied Physics A: Materials Science & Processing》2008,93(2):549-558
(1−x−y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3– yBi0.5Li0.5TiO3 lead-free piezoelectric ceramics have been prepared by an ordinary sintering technique, and their structure, electrical properties,
and temperature characteristics have been studied systematically. The ceramics can be well-sintered at 1050–1150 °C. The increase
in K+ concentration decreases the grain-growth rate and promotes the formation of grains with a cubic shape, while the addition
of Li+ decreases greatly the sintering temperature and assists in the densification of BNT-based ceramics. The results of XRD diffraction
show that K+ and Li+ diffuse into the Bi0.5Na0.5TiO3 lattices to form a solid solution with a pure perovskite structure. As x increases from 0.05 to 0.50, the ceramics transform gradually from rhombohedral phase to tetragonal phase and consequently
a morphotropic phase boundary (MPB) is formed at 0.15≤x≤0.25. The concentration y of Li+ has no obvious influence on the crystal structure of the ceramics. Compared with pure Bi0.5Na0.5TiO3, the partial substitution of K+ and Li+ for Na+ lowers greatly the coercive field E
c and increases the remanent polarization P
r of the ceramics. Because of the MPB, lower E
c and large P
r, the piezoelectricity of the ceramics is improved significantly. For the ceramics with the compositions near the MPB (x=0.15–0.25 and y=0.05–0.10), the piezoelectric properties become optimum: piezoelectric coefficient d
33=147–231 pC/N and planar electromechanical coupling factor k
P=20.2–41.0%. In addition, the ceramics exhibit relaxor characteristic, which probably results from the cation disordering
in the 12-fold coordination sites. The depolarization temperature T
d shows a strong dependence on the concentration x of K+ and reaches the lowest values at the MPB. The temperature dependences of the ferroelectric and dielectric properties at high
temperatures may imply that the ceramics may contain both the polar and non-polar regions at temperatures above T
d. 相似文献
14.
15.
S. A. Uporov N. S. Uporova V. E. Sidorov A. Mikula P. Terzieff 《Journal of Experimental and Theoretical Physics》2009,109(2):269-273
The magnetic susceptibility of Bi100 − x
Mn
x
(x = 5, 7.5, 10, 12.5, 15, 17.5, 20, 25) alloys is experimentally studied by the Faraday method in the temperature range T = 300−1200°C and the magnetic-field range B = 0.6−1.3 T. To calculate the electronic characteristics of the Bi-Mn alloys, the experimental results are approximated by
the generalized Curie-Weiss law. The calculated parameters of the electronic structure of the alloys demonstrate that manganese
is present in the melt in an ionic state with an effective magnetic moment μeff ≈ 5μB, all Bi-Mn alloys have negative paramagnetic temperatures (which indicate the antiferromagnetic character of the exchange
between transition 3d element atoms), and the density of states near the Fermi level n(E
F) is low. Therefore, the Fermi level is outside the d band of manganese and its position is controlled by the sp band of bismuth. 相似文献
16.
K. P. Andryushin A. A. Pavelko I. A. Verbenko O. N. Razumovskaya L. A. Shilkina V. A. Aleshin L. A. Reznichenko 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(8):1082-1084
Ceramic samples of bismuth ferrite and solid solutions of Bi1 − x
A
x
FeO3 type (where A = Lu, Yb, Tm, Er, Ho, Dy, Tb, Gb, Eu, Sm, Nd, Pr, La; 0.05 ≤ x ≤ 0.20; Δx = 0.05) were prepared. Spectra of the real part of electrical conductivity were studied within the range 10−4–10−6 Hz. The dependence of the samples’ thermal stability and electrical conductivity on the size of the substituting ions was
established. 相似文献
17.
Peiqun Zhang L. Urhahn I. Dézsi A. Vantomme G. Langouche 《Hyperfine Interactions》1990,56(1-4):1667-1670
Si(111) single crystals were implanted with57Fe in a broad dose range in order to overlap the concentration range of bulk amorphous Fe
x
Si1−x
samples. At high (≥1016 atoms/cm2) doses the measured hyperfine interaction values were found to be the same as in the bulk amorphous samples, suggesting the
same Fe−Si bonding and a very similar structure for the two amorphous phases produced by different methods. A comparison of
the isomer shift (δ) and quadrupole splitting (ΔE) values with the values of the stoichiometric crystalliine phases showed the same δ but different δE values indicating similar Fe−Si bonding but different atomic arrangement around the iron atom. 相似文献
18.
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
19.
X. Q. Shen J. Xiang F. Z. Song M. Q. Liu 《Applied Physics A: Materials Science & Processing》2010,99(1):189-195
By the electrospinning and calcination techniques, we have prepared uniform nanofibers of Co1−x
Zn
x
Fe2O4 (0.0≤x≤0.5) ferrites with diameters of 110–130 nm. The Co1−x
Zn
x
Fe2O4 nanofibers are single-phase spinels and the lattice constant with Zn content deviates from the Vegard’s law for these Co1−x
Zn
x
Fe2O4 nanofibers. The Co1−x
Zn
x
Fe2O4 nanocrystal grains by which are built nanofibers increase with calcination temperature. Variations of coercivity and saturation
magnetization with calcination temperature can be explained in terms of the grain-size (D) effect. The coercivity (H
c) of Co0.5Zn0.5Fe2O4 nanofibers varies as D
0.65 and basically follows the predicted D
2/3 dependence based on the random anisotropy model in a D range below the single-domain size around 40 nm. The saturation magnetization of Co1−x
Zn
x
Fe2O4 nanofibers initially increases with increasing Zn content, reaches a maximum value at x=0.3 and then decreases with further increase of Zn content, while the coercivity exhibits a continuous reduction with the
increase of Zn content. 相似文献
20.
A semiquantitative model of circular magneto-optical effects in iron garnets is constructed within the concept of charge-transfer transitions and the existing qualitative notions. In the framework of the proposed model, the drastic enhancement of circular magneto-optical effects in R3Fe5O12 iron garnets containing impurities of Bi3+ or Pb2+ ions is explained by the increase in the oxygen contribution to the spin-orbit coupling constant of the (FeO6)9? and (FeO4)5? complexes (the main magneto-optically active centers in iron garnets). This increase is associated with the covalent admixture of the Bi3+ (or Pb2+) 6p orbitals (with a giant one-electron spin-orbit coupling constant) to the oxygen 2p orbitals. The influence of the substitution does not reduce to an enhancement of the oxygen spin-orbit interaction alone but also leads to the appearance of the effective anisotropic tensor contributions to the spin-orbit interaction and circular magneto-optical effects. These contributions to the magneto-optical effects in garnets are estimated. The influence of an inhomogeneous bismuth distribution on the magneto-optical effects in Y3?xBixFe5O12 garnets is investigated using computer simulation. Analysis of the available experimental data on the magneto-optical effects in garnets confirms the validity of the theoretical model proposed. 相似文献