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1.
Wenwei Ge Hong Liu Xiangyong Zhao Xiaobing Li Xiaoming Pan Di Lin Haiqing Xu Xiangping Jiang Haosu Luo 《Applied Physics A: Materials Science & Processing》2009,95(3):761-767
In this paper, a single crystal of 0.96Na0.5Bi0.5TiO3-0.04BaTiO3 with dimensions of Φ 30×10 mm was grown by the top-seeded-solution growth method. X-ray powder diffraction results show that the as-grown crystal
possesses the rhombohedral perovskite-type structure. The dielectric, piezoelectric and electrical conductivity properties
were systematically investigated with 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples. The room-temperature dielectric constants
for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples are found to be 650, 740 and 400 at 1 kHz. The (T
m, ε
m) values of the dielectric temperature spectra are almost independent of the crystal orientations; they are (306°C, 3718),
(305°C, 3613) and (307°C, 3600) at 1 kHz for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal. The optimum poling conditions were
obtained by investigating the piezoelectric constants d
33 as a function of poling temperature and poling electric field. For the 〈001〉 and 〈110〉 crystal samples, the maximum d
33 values of 146 and 117 pC/N are obtained when a poling electric field of 3.5 kV/mm and a poling temperature of 80°C were applied
during the poling process. The as-grown 0.96Na0.5Bi0.5TiO3-0.04BaTiO3 crystal possesses a relatively large dc electrical conductivity, especially at higher temperature, having a value of 1.98×10−11 Ω−1⋅m−1 and 3.95×10−9 Ω−1⋅m−1 at 25°C and 150°C for the 〈001〉 oriented crystal sample. 相似文献
2.
The temperature dependence of the principal values of the refractive index in Sr1−x
CaxTiO3 (x=0.014) has been measured in the 17–275 K range under various conditions of sample illumination with 1.96 eV photons. The
spontaneous photorefractive contribution δn
ph to the temperature-induced variation of the refractive index of Sr1−x
CaxTiO3, which appears after illumination of the sample in the ferrophase (transition temperature T
c=32 K) and persists in the paraphase under heating up to 150 K, has been separated. The photoinduced polarization has been
estimated.
Fiz. Tverd. Tela (St. Petersburg) 39, 711–713 (April 1997) 相似文献
3.
The barium strontium titanate ceramics Ba1 − x
Sr
x
TiO3 with a spatially variable composition has been prepared according to the thick film technology (tape casting). The strontium
content over the film thickness is varied from 0 to 30 mol %. The structure and polarization characteristics of the samples
prepared have been investigated. It has been found that the polarization characteristics of multilayer structures are determined
by the ratio between the thicknesses of layers with different compositions and by their properties. No shift of the hysteresis
loops in the graded thick Ba1 − x
Sr
x
TiO3 (
x
= 0–0.3) films has been revealed. The results obtained have been analyzed in the framework of modern theoretical approaches. 相似文献
4.
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
5.
Theoretical expressions of 〈y
N〉, 〈|y
N − σ1
y
P
c
|〉 and 〈|y
N
2
−σ
1
2
(y
P
c
)2|〉 (wherey
N andy
P
c
are the normalized structure amplitudes of the structure and the model respectively) are derived in terms of the heavy atom
contributionσ
1
2
for monoclinic and orthorhombic crystals containing a few (i.e., 1 or 2) heavy atoms of the same kind per asymmetric unit by taking the heavy atom part alone as the model. Results are obtained
for both the related and unrelated cases. The local values of 〈y
N〉 and 〈|y
N
n
− σ
1
n
(y
P
c
)
n
|〉, (n=1, 2) calculated from these expressions can be used to calculate the overall values of the conventionalR-indicesR(F) andR(I) for the related and unrelated cases. These overall values could be used to check the correctness of heavy atoms located
in the structure.
Contribution No. 550 相似文献
6.
Ba2−x
Sr
x
NaNb5O15 thin films were prepared on La0.05Sr0.95TiO3 substrates by pulsed laser deposition. The structural and ferroelectric properties of the thin films depended on substrate
temperature (T
sub) and Sr concentration. When T
sub was fixed at 700 °C, the Ba2−x
Sr
x
NaNb5O15 (x = 0, 0.6, 1.0, and 1.4) thin films exhibited a high c-axis orientation. The thin films consisted of well-developed grains and exhibited a smooth surface. The c-axis-oriented Ba0.6Sr1.4NaNb5O15 thin film with the lowest Curie temperature also exhibited a high c-axis orientation and a P-E hysteresis loop with a high ferroelectricity at T
sub 650 °C. Thus, its remanent polarization (P
r) and coercive field (E
c) were 2P
r 24.9 μC/cm2 and 2E
c 107 kV/cm, respectively. These values indicate that Ba2−x
Sr
x
NaNb5O15 has ferroelectricity in the thin film form. 相似文献
7.
M. O. Vlasova N. D. Galanina V. S. Demidov A. A. Nedosekin A. Ya. Ostapchuk V. A. Sadykov N. A. Khaldeeva A. L. Endalov M. A. Martem’yanov A. K. Ponosov F. M. Sergeev M. Yu. Tel’nov 《JETP Letters》1996,64(4):258-262
The polarization of the leading Λ hyperons produced on carbon and lead target nuclei by 4–10 GeV neutrons in the angle range
Θ<8.5° with respect to the beam and with only neutral-particle accompaniment is measured: 〈Π〉=−0.096±0.018 for C and 〈Π〉=−
0.128±0.047 for Pb. The dependence of the polarization on the transverse momentum and the Feynman variable is measured. The
normalized invariant cross section as a function of p
⊥
2
is found to be approximated by the function A exp(−Bp
⊥
2
), where the parameter B is independent of the kind of nucleus (B=8.71±0.09 (GeV/c)−2 for carbon and B=8.83±0.18 (GeV/c)−2 for lead).
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 4, 237–240 (25 August 1996) 相似文献
8.
X.H. Zhu H.L.W. Chan C.-L. Choy K.-H. Wong D. Hesse 《Applied Physics A: Materials Science & Processing》2006,82(4):709-713
We report a comparative study of the microstructure of compositionally graded (Ba1-xSrx)TiO3 (BST) films with two compositionally graded directions, up and down, with respect to the substrate, which were deposited
epitaxially on (La,Sr)CoO3 (LSCO)-covered MgO(100) single-crystal substrates by pulsed laser deposition. Cross-sectional transmission electron microscopy
(TEM) images and electron diffraction show that the graded films grow epitaxially with their (100) plane parallel to the (100)
surface of the MgO single-crystal substrate, and with an in-plane orientation relationship of 〈001〉BST//〈001〉LSCO//〈001〉MgO. The crystalline quality and surface morphology of the graded films are closely related to the direction of the compositional
gradient built into the graded films. Down-graded films (starting with a BaTiO3 layer at the film/substrate interface) have a much better crystalline quality and a smoother surface than the up-graded films
(starting with a (Ba0.75Sr0.25)TiO3 layer at the film/substrate interface). Obviously, the BaTiO3 bottom layer in the down-graded film acts not only as a part of the graded film but also as an excellent seeding layer to
enhance the crystallization of the subsequent film layers, resulting in a high crystalline quality of the down-graded film
and an enhanced dielectric behavior. Planar (high-resolution) TEM images also demonstrate that down-graded films have a larger,
and more uniform, grain size than up-graded films, and that the latter contain voids.
PACS 81.15.-z; 77.55.+f; 68.37.Lp; 61.14.-x 相似文献
9.
W. J. Kossler X. H. Yu A. Greer H. E. Schone C. E. Stronach M. Davis R. S. Cary J. E. Crow W. F. Lankford J. Oostens 《Hyperfine Interactions》1991,63(1-4):81-86
Transverse and zero-field μSR measurements were made on YBa2(Cu1−xNix)3O7−y withx=0.1 and 0.2, and YBa2(Cu1−x
Zn
x
)3O7−y
withx=0.03, 0.06, 0.1, and 0.16, wherey≈0.1. Since doping may lead to magnetic ordering this was searched for with both zero and transverse field μSR, but no evidence
was found over the temperature range studied: 10–100 K. However, depolarization rates as functions of temperature were obtained,
and the low temperature values of these are σ=3.2 μs−1.1.6μs−1, and 1 μs−1 forx=0.01, and 0.2 Ni, respectively, and σ=0.8 μs−1, 0.75 μs−1, 0.65 μs−1, and 0.4 μs−1 forx=0.03, 0.06, 0.1, and 0.16 Zn, respectively. Estimates for the effect of decreasing electron concentration for Zn are made,
but these alone do not account for the drop in σ. Estimates for the effect of scattering on λ and hence σ are made. The reduction
in σ for Ni dopant is in surprisingly good agreement with these estimates. For Zn the order of magnitude is correct, but the
relative lack of further change in σ after the effect of the first 0.03 addition seems to imply a saturation of the effect
of scattering. 相似文献
10.
Dielectric properties of ceramic samples of Sr1−x
PbxTiO3 solid solutions for x varying from 0 to 0.3 have been studied. The ferroelectric phase transition in this system has been established to persist
down to x=0.005. Within the x values of 0.002 to 0.05, the ferroelectric transition temperature is shown to follow the relation T
c=A(x−x
c)1/2, with A=440 K and x
c=0.002.
Fiz. Tverd. Tela (St. Petersburg) 39, 714–717 (April 1997) 相似文献
11.
The wave mechanics of two impenetrable hard core particles in a 1-D box is analyzed. Each particle in the box behaves like
an independent entity represented by a macro-orbital (a kind of pair waveform). While the expectation value of their interaction, 〈 V
HC
(x) 〉, vanishes for every state of two particles, the expectation value of their relative separation, 〈 x 〉, satisfies 〈 x 〉≥λ/2 (or q ≥ π/d, with 2d=L being the size of the box). The particles in their ground state define a close-packed arrangement of their wave packets (with
〈 x 〉= λ/2, phase position separation Δϕ = 2π and momentum |q
o| = π/d) and experience a mutual repulsive force (zero point repulsion) f
o
=h
2/2md
3 which also tries to expand the box. While the relative dynamics of two particles in their excited states represents usual
collisional motion, the same in their ground state becomes collisionless. These results have great significance in determining
a correct microscopic understanding of widely different many-body systems. 相似文献
12.
A. E. Nikiforov A. Yu. Zakharov V. A. Chernyshev M. Yu. Ugryumov S. V. Kotomanov 《Physics of the Solid State》2003,45(5):864-867
The structure of the mixed fluorites Ca1−x
SrxF2 and Sr1−x
BaxF2, as well as the structure of the Eu2+ impurity center in these crystals, is calculated within the framework of the virtual-crystal method realized in the shell
model and pair-potential approximation. The phenomenological dependence of the position of the lower level of the 4f
65d configuration of the Eu2+ ion on distance to the Eu2+-ligand is derived. The dependences of the Stokes shift and the Huang-Rhys factor on x are calculated for the yellow luminescence in Sr1−x
BaxF2:Eu2+. The value of x at which the lower level of the 4f
65d configuration of the Eu2+ ion in Sr1−x
BaxF2:Eu2+ falls within the conduction band is found.
__________
Translated from Fizika Tverdogo Tela, Vol. 45, No. 5, 2003, pp. 823–826.
Original Russian Text Copyright ? 2003 by Nikiforov, Zakharov, Chernyshev, Ugryumov, Kotomanov. 相似文献
13.
A. S. Barabash 《Physics of Atomic Nuclei》2010,73(1):162-178
The present status of double-beta-decay experiments (including the search for 2β
+, ECβ
+, and ECEC processes) are reviewed. The results of the most sensitive experiments are discussed. Average and recommended half-life
values for two-neutrino double-beta decay are presented. Conservative upper limits on effective Majorana neutrino mass and
the coupling constant of the Majoron to the neutrino are established as 〈m
ν
〉 < 0.75 eV and 〈g
ee
〉 < 1.9 × 10−4, respectively. Proposals for future double-betadecay experiments with a sensitivity for the 〈m
ν
〉 at the level of 0.01–0.1 eV are considered. 相似文献
14.
The vibration frequencies of unstable ferroelectric and antiferrodistortion modes and the dependences of the energy on the
ion displacement amplitude have been calculated within the generalized Gordon-Kim model for distortions along eigenvectors
of these modes in the mixed compounds Sr1 − x
A
x
Ti1 − x
/4□
x/4O3 and Sr1 − y
A
2y
/3□
y/3TiO3 (A = Sc3+, In3+, La3+, Bi3+; □ is the vacancy). To compensate an excess positive charge, vacancies are introduced into the Ti4+ or Sr2+ site. Calculations have been performed in the “daverage” crystal approximation for impurity concentrations of 0.25 and 0.50.
To this end, a set of 40 atomic superlattices with various orderings of heterovalent ions Sr2+ and impurity A
3+ has been considered. It has been found that each impurity type, independently of charge balance, induces ferroelectric instabilities
in doped compounds. In the case of doping with In3+ and La3+ for concentration x = 0.25, the possibility of rotating the polarization vector has been shown. 相似文献
15.
Xiaorong Cheng 《Solid State Communications》2007,141(11):587-590
The dielectric and ferroelectric properties of (BaxSr1−x)0.77Ca0.23TiO3 ceramics with x=1 to 0.7 were studied and compared with those of BaxSr1−xTiO3 and Ba0.77Ca0.23TiO3 ceramics. It has been found that Sr doping of the Ba0.77Ca0.23TiO3 ceramics causes a drastic decrease of the Curie temperature, just like Sr doping of pure BaTiO3 ceramics, demonstrating a cell volume effect. However, the (BaxSr1−x)0.77Ca0.23TiO3 ceramics with x=0.9 and 0.8 have larger spontaneous polarization than those of the corresponding BaxSr1−xTiO3 and Ba0.77Ca0.23TiO3 ceramics, along with sufficient insulating properties. The enhancement of their polarization was explained by the increase of the lattice parameter c/a ratio due to the lattice distortion and strain developed in the ceramics. 相似文献
16.
N. I. Sorokin M. V. Fominykh E. A. Krivandina Z. I. Zhmurova B. P. Sobolev O. I. Lyamina 《Physics of the Solid State》1998,40(4):604-607
The fluoride-ion conductivity of the nonstoichiometric tysonite phases La0.95(Ba1−x
Srx)0.05Fe2.95 (0⩽x⩽1) is investigated by impedance spectroscopy. Electrophysical measurements are performed in the frequency range 5–5×105 Hz and temperature range 300–700 K. A discontinuity is observed in the temperature dependence of the conductivity at T
c=410–430 K. The behavior of the temperature dependence of the electrical conductivity is explained within a transport model
taking into account the migration of fluoride ions between different inequivalent structural sites. The maximum value of the
conductivity at room temperature (293 K) is 2×10−4 Ω−1 cm−1 for the solid solution La0.95Sr0.05F2.95. The fluorine-ion conductivity in La0.95(Ba1−x
Srx)0.05F2.95 single crystals is almost an order of magnitude larger than the value for the commercial solid electrolyte La0.992Eu0.008F2.992 (a fluorine-selective membrane) having a tysonite structure.
Fiz. Tverd. Tela (St. Petersburg) 40, 658–661 (April 1998) 相似文献
17.
Yu. A. Abrahamian G. G. Karamian V. I. Serago V. I. Stafeyev 《International Journal of Infrared and Millimeter Waves》1997,18(12):2315-2322
Photoconductivity of single crystal Pb1−xSnxTe〈In〉, (0.24≤x≤0.25), films at 4.2K in the wavelength region 4÷5 mm and magnetic fields up to 8 T was studied. Preparation
technology of the films with high photoconductivity (PFEP ≤ 10−12 W×Hz1/2) and photoresponsiveness (τ ≤ 10−6 s), as well as the measurements procedure are described in the paper. Also the mechanism of photoconductivity is discussed. 相似文献
18.
A group of position-thickness-dependent stresses are used to modified Landau-Devonshire theory to investigate the second-order
phase transition in Ba1−x
Sr
x
TiO3 films. The result shows that the short-range interaction between the unit cells of the film and the substrate induces the
phase transition dispersion and the rise of the transition temperature in the films. The dependence of the effective dielectric
constant on the temperature and the average spontaneous polarization on the film thickness are computed, which qualitatively
agree with the experiments.
相似文献
19.
M. I. Daunov I. K. Kamilov A. B. Magomedov 《Journal of Experimental and Theoretical Physics》1997,84(2):309-316
We use the data on the pressure (up to P=1.5 GPa) and field (up to H=17 kOe) dependence of the Hall coefficient and the resistivity at 77.6 and 300 K in p-CdSnAs2〈Cu〉 to calculate the effective kinetic characteristics of the charge carriers, the density and mobility of the conduction
electrons and the holes of the deep acceptor and valence bands, in an interval of excess-acceptor densities N
ext ranging from 1010–1017 cm−3. We establish that in a heavily doped semiconductor with a deep impurity band at the tail of the density of states of the
intrinsic band, with unequal donor and acceptor densities, a a heavily doped and fully compensated semiconductor state is
realized under hydrostatic compression. The threshold value of the pressure that initiates the transition into such a state,
P
c, depends on the extent to which the impurity band is populated. In p-CdSnAs2〈Cu〉 at N
ext=N
A, where N
A is the density of deep acceptors, and T⩽77.6 K the value of P
c amounts to 10−4 GPa. As the population of the deep acceptor band grows, P
c increases and in the limit becomes infinite. We discuss the special features of the electrophysical properties of p-CdSnAs2〈Cu〉 arising from the absence of an energy gap between the states of the conduction band and those of the deep acceptor band.
Zh. éksp. Teor. Fiz. 111, 562–574 (February 1997) 相似文献
20.
P. Zh. Aslanyan V. N. Emelyanenko G. G. Rikhkvitzkaya 《Physics of Particles and Nuclei Letters》2007,4(1):60-66
The experimental data from the 2-m propane bubble chamber have been analyzed for pC → Λ(K
s
0
)X reactions at 10 GeV/c. The estimation of experimental inclusive cross sections for Λ and K
s
0
production in the p
12C collision is equal to σΛ = (13.3 ± 1.7) mb and σ
K
s
0
= (4.6 ± 0.6) mb, respectively. The measured 〈Λ〉/〈π+〉 ratio from pC reaction is equal to (5.3 ± 0.8) × 10−2, and it is approximately two times larger than the 〈Λ〉/〈π+〉 ratio simulated by the FRITIOF model and than that of experimental pp reactions at the same energy.
The text was submitted by the authors in English. 相似文献