共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
V.M. Sreekumar R.M. Pillai B.C. Pai M. Chakraborty 《Applied Physics A: Materials Science & Processing》2008,90(4):745-752
The present study analyzes the morphological transformations of reaction products i.e., MgO, MgAl2O4 occurring during the reaction between SiO2 and Al-Mg alloy in Al-Mg-SiO2 composite processed by the liquid metallurgy technique. Different phases of platelet and hexagonal morphologies are detected
and their composition analysis by EDS has confirmed them as being transition phases existing between MgO, MgAl2O4 and Al2O3. This study has also revealed the gradual transformation of (i) MgO needles to octahedral MgAl2O4 through Mg-Al-Si-O and Mg-Al-O transition phases having platelet morphologies and (ii) MgAl2O4 to Al2O3 through hexagonal transition phases on holding of Al-5Mg-SiO2 and Al-1Mg-SiO2 composites respectively at 1023K. Fully developed α-Al2O3 crystals are not observed under the present experimental conditions, wherein the Mg content is well above the equilibrium
Mg content required for the formation of stable Al2O3 (<0.05 wt. %).
PACS 05.70.Np 相似文献
3.
H. Cherkani-Hassani S. Cherkani-Hassani D. S. Belic J. J. Jureta J. Lecointre P. Defrance 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,58(1):75-83
Absolute cross-sections for electron-impact ionization and dissociation of
C2H2+ and C2D2+ have been measured for electron energies
ranging from the corresponding thresholds up to 2.5 keV. The animated
crossed beams experiment has been used. Light as well as heavy fragment ions
that are produced from the ionization and the dissociation of the target
have been detected for the first time. The maximum of the cross-section for
single ionization is found to be (5.56 ± 0.03)× 10-17 cm2 around 140 eV. Cross-sections for dissociation of C2
H2+ (C2D2+) to ionic products are seen to decrease for two orders
of magnitude, from C2D+ (12.6 ± 0.3) × 10-17 cm2 over CH+(9.55 ± 0.06) × 10-17 cm2,
C+ (6.66 ± 0.05) × 10-17 cm2, C2+ (5.36 ± 0.27) × 10-17 cm2, H+ (4.73 ±
0.29) × 10-17 cm2 and CH2+ (4.56 ± 0.27) × 10-18 cm2 to H2+ (5.68 ± 0.49) ×
10-19 cm2. Absolute
cross-sections and threshold energies have been compared with the scarce
data available in the literature. 相似文献
4.
Tingyin Ning Cong Chen Yueliang Zhou Heng Lu Dongxiang Zhang Hai Ming Guozhen Yang 《Applied Physics A: Materials Science & Processing》2009,94(3):567-570
CaCu3Ti4O12 (CCTO) thin films were successfully prepared on LaAlO3 substrates by pulsed laser deposition technique. We measured the nonlinear optical susceptibility of the thin films using
Z-scan method at a wavelength of 532 nm with pulse durations of 25 ps and 7 ns. The large values of the third-order nonlinear
optical susceptibility, χ
(3), of the CCTO film were obtained to be 2.79×10−8 esu and 3.30×10−6 esu in picosecond and nanosecond time regimes, respectively, which are among the best results of some representative nonlinear
optical materials. The origin of optical nonlinearity of CCTO films was discussed. The results indicate that the CCTO films
on LaAlO3 substrates are promising candidate materials for applications in nonlinear optical devices. 相似文献
5.
Jian Shen Jonathon B. Clemens Evgueni A. Chagarov Darby L. Feldwinn Wilhelm Melitz Tao Song Sarah R. Bishop Andrew C. Kummel Ravi Droopad 《Surface science》2010,604(19-20):1757-1766
The structural and electronic properties of group III rich In0.53Ga0.47As(001) have been studied using scanning tunneling microscopy/spectroscopy (STM/STS). At room temperature (300 K), STM images show that the In0.53Ga0.47As(001)–(4 × 2) reconstruction is comprised of undimerized In/Ga atoms in the top layer. Quantitative comparison of the In0.53Ga0.47As(001)–(4 × 2) and InAs(001)–(4 × 2) shows the reconstructions are almost identical, but In0.53Ga0.47As(001)–(4 × 2) has at least a 4× higher surface defect density even on the best samples. At low temperature (77 K), STM images show that the most probable In0.53Ga0.47As(001) reconstruction is comprised of one In/Ga dimer and two undimerized In/Ga atoms in the top layer in a double (4 × 2) unit cell. Density functional theory (DFT) simulations at elevated temperature are consistent with the experimentally observed 300 K structure being a thermal superposition of three structures. DFT molecular dynamics (MD) show the row dimer formation and breaking is facilitated by the very large motions of tricoodinated row edge As atoms and z motion of In/Ga row atoms induced changes in As–In/Ga–As bond angles at elevated temperature. STS results show there is a surface dipole or the pinning states near the valence band (VB) for 300 K In0.53Ga0.47As(001)–(4 × 2) surface consistent with DFT calculations. DFT calculations of the band-decomposed charge density indicate that the strained unbuckled trough dimers being responsible for the surface pinning. 相似文献
6.
H. Cherkani-Hassani D. S. Belic J. J. Jureta J. Lecointre P. Defrance 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,58(1):85-94
Absolute cross-sections for electron-impact dissociative ionization of C2
H2+ and C2 D2+ to CH+, C+, C2+ , H+, CH2+
and C2D+ fragments are determined for electron energies ranging
from the corresponding threshold to 2.5 keV. Results obtained in a crossed
beams experiment are analyzed to estimate the contribution of dissociative
ionization to each fragment formation. The dissociative ionization cross
sections are seen to decrease for more than an order of magnitude, from
CH+ (5.37±0.10) × 10-17 cm2 over C+ (4.19±
0.16) × 10-17 cm2, C2D+ (3.94±0.38) ×
10-17 cm2, C2+ (3.82±0.15) × 10-17 cm2
and H+ (3.37±0.21) × 10-17 cm2 to CH2+
(2.66±0.14) × 10-18 cm2. Kinetic energy release
distributions of fragment ions are also determined from the analysis of the
product velocity distribution. Cross section values, threshold energies and
kinetic energies are compared with the data available from the literature.
Conforming to the scheme used in the study of the dissociative excitation of
C2H2+
( C2 D2+ )\left( {\rm C}_2 {\rm D}_2^+ \right), the cross-sections are presented in
a format suitable for their implementation in plasma simulation codes. 相似文献
7.
V. P.S. Awana A. Vajpayee M. Mudgel V. Ganesan A. M. Awasthi G. L. Bhalla H. Kishan 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):281-294
We report synthesis, structure/micro-structure, resistivity under magnetic
field [ρ(T)H], Raman spectra, thermoelectric power S(T), thermal conductivity
κ(T), and magnetization of ambient pressure argon annealed
polycrystalline bulk samples of MgB2, processed under identical
conditions. The compound crystallizes in hexagonal structure with space
group P6/mmm. Transmission electron microscopy (TEM) reveals electron micrographs
showing various types of defect features along with the presence of 3–4 nm
thick amorphous layers forming the grain boundaries of otherwise crystalline
MgB2. Raman spectra of the compound at room temperature exhibited
characteristic phonon peak at 600 cm-1. Superconductivity is observed
at 37.2 K by magnetic susceptibility χ(T), resistivity ρ(T), thermoelectric power
S(T), and thermal conductivity κ(T) measurements. The power law fitting
of ρ(T) give rise to Debye temperature (ΘD) at 1400 K which is
found consistent with the theoretical fitting of S(T), exhibiting Θ
D of 1410 K and carrier density of 3.81 × 1028/m3. Thermal
conductivity κ(T) shows a jump at 38 K, i.e., at Tc, which was
missing in some earlier reports. Critical current density (Jc) of up to
105 A/cm2 in 1–2 T (Tesla) fields at temperatures (T) of up to 10 K
is seen from magnetization measurements. The irreversibility field, defined
as the field related to merging of M(H) loops is found to be 78, 68 and 42 kOe
at 4, 10 and 20 K respectively. The superconducting performance parameters
viz. irreversibility field (Hirr) and critical current density
Jc(H) of the studied MgB2 are improved profoundly with addition of
nano-SiC and nano-diamond. The physical property parameters measured for
polycrystalline MgB2 are compared with earlier reports and a
consolidated insight of various physical properties is presented. 相似文献
8.
Y. Xiao Y. Su C. M. N. Kumar C. Ritter R. Mittal S. Price J. Perßon Th. Brückel 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,82(2):113-121
The physical and structural properties of Fe1.11Te and
Fe1.11Te0.5Se0.5 have been investigated by means of
X-ray and neutron diffraction as well as physical property
measurements. For the Fe1.11Te compound, the structure
distortion from a tetragonal to monoclinic phase takes place at 64 K
accompanied with the onset of antiferromagnetic order upon cooling.
The magnetic structure of the monoclinic phase was confirmed to be
of antiferromagnetic configuration with a propagation vector
k = (1/2, 0, 1/2) based on Rietveld refinement of neutron
powder diffraction data. The structural/magnetic transitions are
also clearly visible in magnetic, electronic and thermodynamic
measurements. For superconducting Fe1.11Te0.5Se0.5
compound, the superconducting transition with T
c
= 13.4 K
is observed in the resistivity and ac susceptibility measurements.
The upper critical field H
c2 is obtained by measuring
the resistivity under different magnetic fields. The Kim’s critical
state model is adopted to analyze the temperature dependence of the
ac susceptibility and the intergranular critical current density is
calculated as a function of both field amplitude and temperature.
Neutron diffraction results show that
Fe1.11Te0.5Se0.5 crystalizes in tetragonal structure
at 300 K as in the parent compound Fe1.11Te and no structural
distortion is detected upon cooling to 2 K. However an anisotropic
thermal expansion anomaly is observed around 100 K. 相似文献
9.
J.-E. Jørgensen L. Keller 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(4):445-453
The crystal and magnetic structures of
Dy1-xCaxBaCo2O5.5
for x = 0.0 and 0.1 have been studied by neutron powder diffraction and the
crystal structures of both compounds were found to be best described in
space group Pmmm with a ap × 2ap × 2ap unit cells where ap is the lattice parameter
of the cubic perovskite unit cell. The a- and b-axes were found to decrease
and increase abruptly between 315 and 350 K as the temperature
increases and the unit cell volumes exhibit signs of excess thermal
expansion in the temperature range from 260 to 315 K.
Dy0.9Ca0.1BaCo2O5.5
orders antiferromagnetically for T ≤ 305 K into a G-type magnetic
structure with a 2ap × 2ap × 2ap
magnetic unit cell. DyBaCo2O5.5 exhibits two
magnetically ordered phases and a G-type magnetic structure was observed at
the investigated temperatures 260 and 290 K. A 2ap ×
2ap × 4ap magnetic unit cell was needed for
indexing of the magnetic reflections observed for T ≤ 230 K. The
low temperature magnetic structure of
DyBaCo2O5.5 is different from the observed
magnetic structures of TbBaCo2O5.5 and
HoBaCo2O5.5 despite the proximity of Tb, Dy and
Ho in the periodic table. It is a relatively complex antiferromagnetic
structure with both pyramidally and octahedrally coordinated Co ions in the
intermediate spin state. It contains both ferro- and antiferromagnetic
interactions and the magnetic moments are canted in the
a, b-plane. The canting
angles between the magnetic moments and the
b-axis are 6.6 and 50.0° at 20 K for the
pyramidally and octahedrally coordinated Co ions, respectively. The high and
low temperature magnetic phases were found to coexist at 230 K. 相似文献
10.
C. Wang N. Srivastava 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(3):465-477
OH radical number density in multiple atmospheric pressure microwave plasma
jets is measured using UV cavity ringdown spectroscopy of the OH (A–X) (0–0) band at 308 nm. The plasma cavity was excited
by a
2.45 GHz microwave
plasma source and plasma jets of 2–12 mm long were generated by using
three different plasma gases, argon (Ar), Ar/N2, and Ar/O2.
Comparative characterization of the plasma jets in terms of plasma shape,
stability, gas temperature, emission intensities of OH, NO, and N2, and
absolute number density of the OH radical was carried out under different
plasma gas flow rates and powers at various locations along the plasma jet
axis. With three different operating gases, the presence of OH radicals in
all of the plasma jets extended to the far downstream. As compared to the
argon plasma jets, the plasma jets formed with Ar/N2 and Ar/O2 are more diffuse and less stable. Plasma gas temperatures along
the jet axis were measured to be in the range of 470–800 K for all of the
jets formed in the different gas mixtures. In each plasma jet, OH number
density decreases along the jet axis from the highest OH density in the
vicinity of the jet tip to the lowest in the far downstream. OH density
ranges from 1.3 × 1012 to 1.1 × 1016, 4.1 ×
1013 to 3.9 × 1015, and 7.0 × 1012 to 4.6
× 1016 molecule/cm3 in the Ar, Ar/N2, and Ar/O2
plasma jets, respectively. The OH density dependence on plasma power and gas
flow rate in the three plasma jets is also investigated. 相似文献
11.
S. Vatnik M. C. Pujol J. J. Carvajal X. Mateos M. Aguiló F. Díaz V. Petrov 《Applied physics. B, Lasers and optics》2009,95(4):653-656
The three thermo-optic coefficients of the biaxial laser host KLu(WO4)2 are measured at 633 nm by a deflection method. Their values at 300 K amount to ∂
n
g
/∂
T=−7.4×10−6 K−1; ∂
n
m
/∂
T=−1.6×10−6 K−1 and ∂
n
p
/∂
T=−10.8×10−6 K−1. Nearly athermal propagation directions are found for polarizations along the N
m
and N
p
dielectric axes. 相似文献
12.
D. P. Kozlenko N. T. Dang Z. Jirák S. E. Kichanov E. V. Lukin B. N. Savenko L. S. Dubrovinsky C. Lathe C. Martin 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,77(3):407-411
The crystal and magnetic structures of Pr0.15Sr0.85MnO3
manganite have been studied by means of powder X-ray and neutron diffraction
in the temperature range 10–400 K at high external pressures up to 55 and 4 GPa, respectively. A structural phase transition
from cubic to tetragonal
phase upon compression was observed, with large positive pressure
coefficient of transition temperature dT
ct
/dP = 28(2) K/GPa. The C-type
antiferromagnetic (AFM) ground state is formed below T
N
≈ 260 K
at ambient pressure. While at ambient pressure the structural and magnetic
transition temperatures are close, T
ct
~ T
N
, upon compression
they become decoupled with T
N
≪ T
ct
due to much weaker
T
N
pressure dependence with coefficient dT
N
/dP = 3.8(1) K/GPa. 相似文献
13.
A molecular dynamics (MD) simulation study has been performed for the rapid solidification of Cu70Ni30 adopting the quantum Sutton-Chen many-body potentials. By analyzing the bond-types and the relation of atomic average energy
versus temperature, it was demonstrated that as cooling rate being 2×1012 K/s, the Cu70Ni30 formed fcc crystal structures and freezing point was found. In addition, having analyzed the transformation of microstructures
and the detail of crystal growth by using atomic trace and visual method, not only could the formation of binary disordered
solid solution be showed, but also the solidification of liquid metals and the crystal growth processes could be, further
understood. 相似文献
14.
Epitaxial BaFe1.8Cr0.2As2 thin films with the tetragonal c-axis perpendicular to the thin film surface were grown on (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) single crystalline substrates using pulsed laser deposition (PLD). Resistive measurements indicate the existence of two transitions at temperatures of about 80 K and 40 K. The transition at 80 K is attributed to the structural transition from the high temperature tetragonal phase to the low temperature orthorhombic phase accompanied with the magnetic transition from a paramagnetic to an antiferromagnetic state as known for doped bulk systems. Below T ≈ 40 K the magnetization curves measured perpendicularly to the orthorhombic c-axis in fields up to 9 Tesla show two inflexion points indicating metamagnetic transitions. 相似文献
15.
Magnetic anisotropies of 20 nm epitaxial film of palladium–iron alloy Pd0.92Fe0.08 grown on the (001) MgO substrate were studied. Ferromagnetic resonance (FMR) spectroscopy and vibrating sample magnetometry (VSM) were exploited to determine magnetic parameters of the film. It was found that the synthesized film reveals cubic anisotropy with tetragonal distortion. The simulated magnetic hysteresis loops, obtained utilizing the magnetic anisotropy constants taken from the FMR spectra analysis, agree well with those measured by VSM. 相似文献
16.
A new member of the family of garnets with fast lithium ion conduction has been found with the composition Li7La3Hf2O12. The anion arrangement corresponds to the oxygen framework in garnets, e.g., in Ca3Fe2Si3O12. Hafnium is coordinated octahedrally while the lanthanum environment can be described as a distorted cube. Lithium occupies
a large number of positions with tetrahedral, trigonal planar, and metaprismatic coordination. Li7La3Hf2O12 shows a lithium bulk ion conductivity of 2.4 × 10−4 Ω−1 cm−1 at room temperature with an activation energy of 0.29 eV. 相似文献
17.
V. Kusigerski D. Markovic V. Spasojevic M. Tadic M. Zentkova M. Mihalik 《Journal of nanoparticle research》2010,12(4):1299-1306
Pressure effects on magnetic properties of two La0.7Ca0.3MnO3 nanoparticle samples with different mean particle sizes were investigated. Both the samples were prepared by the glycine-nitrate
method: sample S—as-prepared (10 nm), and sample S900—subsequently annealed at 900 °C for 2 h (50 nm). Magnetization measurements revealed remarkable differences in magnetic properties
with the applied pressure up to 0.75 GPa: (i) for S sample, both transition temperatures, para-to-ferromagnetic T
C = 120 K and spin-glass-like transition T
f = 102 K, decrease with the pressure with the respective pressure coefficients dT
C/dP = −2.9 K/GPa and dT
f/dP = −4.4 K/GPa; (ii) for S900 sample, para-to-ferromagnetic transition temperature T
C = 261 K increases with pressure with the pressure coefficient dT
C/dP = 14.8 K/GPa. At the same time, saturation magnetization M
S recorded at 10 K decreases/increases with pressure for S/S900 sample, respectively. Explanation of these unusual pressure effects on the magnetism of sample S is proposed within the scenario
of the combined contributions of two types of disorders present in the system: surface disorder introduced by the particle
shell, and structural disorder of the particle core caused by the prominent Jahn–Teller distortion. Both disorders tend to
vanish with the annealing of the system (i.e., with the nanoparticle growth), and so the behavior of the sample S900 is similar to that previously observed for the bulk counterpart. 相似文献
18.
V. P. Dyakonov R. Szymczak A. D. Prokhorov E. Zubov A. A. Prokhorov G. Petrakovskii L. Bezmaternikh M. Berkowski V. Varyukhin H. Szymczak 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(3):291-298
Magnetic and electron paramagnetic resonance (EPR) properties of
EuFe3(BO3)4 single crystals have been studied over the
temperature range of 300–4.2 K and in a magnetic field up to 5 T. The
temperature, field and orientation dependences of susceptibility,
magnetization and EPR spectra are presented. An antiferromagnetic ordering
of the Fe subsystem occurs at about 37 K. The easy direction of
magnetization perpendicular to the c axis is determined by magnetic
measurements. Below 10 K, we observe an increase of susceptibility connected
with the polarization of the Eu sublattice by an effective exchange field of
the ordered Fe magnetic subsystem. In a magnetic field perpendicular to the
c axis, we have observed an increase of magnetization at T < 10 K in the
applied magnetic field, which can be attributed to the appearance of the
magnetic moment induced by the magnetic field applied in the basal plane.
According to EPR measurements, the distance between the maximum and minimum
of derivative of absorption line of the Lorentz type is equal to 319 Gs. The
anisotropy of g-factor and linewidth is due to the influence of crystalline
field of trigonal symmetry. The peculiarities of temperature dependence of
both intensity and linewidth are caused by the influence of excited states
of europium ion (Eu3+). It is supposed that the difference between the
g-factors from EPR and the magnetic measurements is caused by exchange
interaction between rare earth and Fe subsystems via anomalous Zeeman
effect. 相似文献
19.
Xinghua Zheng Lin Qiu Guoping Su Dawei Tang Yuchao Liao Yunfa Chen 《Journal of nanoparticle research》2011,13(12):6887-6893
A 3ω approach for the simultaneous determination of the effective thermal conductivity and thermal diffusivity of nanopowder
materials was developed. A 3ω experimental system was established, and the thermal properties of water and alcohol were measured
to validate and estimate the accuracy of the current experimental system. The effective thermal conductivity and thermal diffusivity
of the SiO2 nanopowder with 375, 475, and 575 nm diameters were measured at 290–490 K and at different densities. At room temperature,
the effective thermal conductivity and thermal diffusivity of the SiO2 nanopowder increased with temperature; however, both values decreased as the particle diameter was reduced. An optimum SiO2 powder density that decreased with decreasing diameter was also observed within the measurement range. The minimum effective
thermal conductivity and maximum effective thermal diffusivity were obtained at 85 × 10−3 kg/L, when the particle diameter was 575 nm. The optimum densities of the particles with 375 and 475 nm diameters were less
than 50.23 × 10−3 and 64.82 × 10−3 kg/L, respectively. 相似文献
20.
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