共查询到20条相似文献,搜索用时 906 毫秒
1.
V.V. Atuchin D. Dimova-Malinovska T.I. Grigorieva I.E. Kalabin I. Savatinova I. Savova E.V. Spesivtsev S. Tonchev C.C. Ziling 《Applied physics. B, Lasers and optics》2001,73(5-6):559-563
The formation of high-temperature phases in low-doped H:LiTaO3 waveguide layers in Z-cut LiTaO3 has been observed both by refractive-index and IR-spectra measurements. This permits us to correlate the index jumps to the
changes of the OH bonds in the crystal lattice. Reversible phase transitions were detected in the temperature interval T=50–200 °C
over a wide range of hydrogen content including as-grown LiTaO3. The high-temperature phases are metastable close to room temperature. This was demonstrated by tracing the time evolution
of the refractive-index change. It was shown that the high-temperature phases are responsible for the long-term refractive-index
instabilities in both H:LiTaO3 waveguides and virgin LiTaO3.
Received: 7 May 2001 / Revised version: 10 August 2001 / Published online: 30 October 2001 相似文献
2.
Y.N. Korkishko V.A. Fedorov A.N. Alkaev F. Laurell 《Applied physics. B, Lasers and optics》2001,73(5-6):519-522
A detailed correlation between the fabrication conditions, crystallographic phase state of HxLi1-xTaO3 waveguides and second-order optical non-linearity has been investigated by using reflected SHG measurements from the polished
waveguide end face. The non-linearity, strongly reduced after the initial proton exchange, is found to be restored and even
increased after annealing. However, this apparent increase in the non-linearity is accompanied by a strong degradation of
the quality of the SHG reflected beam in the region of the initial as-exchanged waveguide due to beam scattering. The high
temperature proton exchange technique has been shown to produce high-quality α-phase waveguides with essentially undegraded
non-linear optical properties. There is no phase transition when the α-phase waveguides are fabricated by direct exchange.
This phase presents the same crystalline structure as that of LiTaO3 and maintains the excellent non-linear properties of the bulk material. The results obtained are important for the design,
fabrication and optimization of guided-wave non-linear optical devices in LiTaO3.
Received: 21 May 2001 / Published online: 23 October 2001 相似文献
3.
Yu.N. Korkishko V.A. Fedorov S.M. Kostritskii 《Applied physics. B, Lasers and optics》1998,67(5):577-581
i -HxLi1-xNbO3 phases generated on x-cut LiNbO3 the new anisotropic libration mode at 890–940 cm-1 is observed in addition to the known isotropic mode at 960–970 cm-1, whereas the same phases on z-cut exhibit only latter isotropic libration mode. The observed phenomena are explained as a result
of anisotropic stresses generated in the x-cut waveguides, whereas the stresses in the structures on z-cut are isotropic.
The OH-bond librations are clearly anisotropic in the α, κ1, and κ2 phases generated on both z- and x-cuts, which indicates a fundamental difference of the local symmetry of the proton’s position
in the βi phases compared to the α, κ1, and κ2 HxLi1-xNbO3 phases.
Received: 4 May 1998/Revised version: 26 June 1998 相似文献
4.
High pressure Raman spectroscopic studies on Gd2(MoO4)3(GMO) have been carried out at ambient temperature in the diamond cell to 10 GPa hydrostatic pressure. These experiments have
revealed pressure-induced phase transitions in GMO near 2 GPa and 6.0 GPa. The first transition is from Pba2(β′) phase to another undetermined crystalline phase, designated as phase II, and the second transition is to an amorphized
state. On releasing pressure there is a partial reversion to the crystalline state. The Raman data indicate that the amorphization
is due to disordering of the MoO4 tetrahedral units. Further, it is inferred from the nature of the Raman bands in the amorphized material that the Mo-O bond
lengths and bond angles have a range of values, instead of a few set values. The results of the present study as well as previous
high pressure-high temperature quenching experiments strongly support that pressure-induced amorphization in GMO is a consequence
of the kinetically impededβ toα phase transition. The system in frustration becomes disordered. The rare earth trimolybdates crystallizing in theβ′ structure are all expected to undergo similar pressure-induced amorphization. 相似文献
5.
Shingo Kanehira Masaaki Sakakura Yasuhiko Shimotsuma Masaaki Eida Kiyotaka Miura Kazuyuki Hirao 《Applied Physics A: Materials Science & Processing》2010,101(1):81-85
Phase control of Fe–Si amorphous thin film in micro area is demonstrated using femtosecond laser irradiation. A femtosecond
laser beam with a high repetition rate over 200 kHz and tightly focused through an objective lens promotes both crystallization
and phase transformation from an amorphous phase into crystalline β-FeSi2, α-FeSi2, or ε-FeSi phases. Formation of each crystalline phase is possible by changing the pulse energy or the scanning speed of the incident
laser beam. 相似文献
6.
S. Firmino?Mendes C. M. Costa V. Sencadas J. Serrado?Nunes P. Costa R. Gregorio J. L. Gomez Ribelles S. Lanceros-Méndez 《Applied Physics A: Materials Science & Processing》2009,96(4):1037-908
In this work, poly(vinilidene fluoride)/Pb(Zr0.53Ti0.47)O3([PVDF]1−x
/[PZT]
x
) composites of volumetric fractions x and (0–3) type connectivity were prepared in the form of thin films. PZT powder of crystallite size of 0.84, 1.68, and 2.35
μm in different amounts of PZT (10, 20, 30, and 40%) was mixed with the polymeric matrix. The crystalline phase of the polymeric
matrix was the nonpolar α-phase and the polar β-phase.
Dielectric and dynamic mechanical (DMA) measurements were performed to these composites in order to evaluate the influence
of particle size and the amount of PZT filler with respect to the PVDF matrix. The inclusion of ceramic particles in the PVDF
polymer matrix increases the complex dielectric constant and dynamical mechanical response of the composites. A similar behavior
is observed for the α- or β-phase of the polymeric matrix indicating that the PVDF polymer matrix is not particularly relevant for the composite behavior.
On the other hand, ceramic size and especially content play the major role in the increase of the dielectric response and
the room temperature storage modulus. In particular, the storage modulus increases with increasing PZT concentration, but
this increase is more pronounced, in terms of maximum value, for the sample with 2.35 μm particle size; DMA reveals two main
relaxations in the analyzed samples. A low-temperature process maximum at ca. −40°C, usually labeled by β or α
a
associated to the T
g
of the polymer and the α-relaxation at temperatures above 30°C. The β-relaxation is also observed in the dielectric measurements.
The models used to asses the dielectric behavior of the samples with increasing PZT concentration indicate that the particle–matrix
interaction plays a relevant role, as well as the particle asymmetry and relative orientation, being the Yamada model the
most appropriate to describe the composite behavior.
An erratum to this article can be found at 相似文献
7.
Y. Yan J. Y. Zhang T. Cui Y. Li Y. M. Ma J. Gong Z. G. Zong G. T. Zou 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(4):397-403
The lattice dynamics of lithium nitride (Li3N) under high pressure are extensively investigated to probe its phase transformations by using the pseudopotential plane-wave
method within the density functional theory. A new second order α↦α′-Li3N phase transition is identified for the first time. The newly proposed α′-phase possesses a hexagonal symmetry with four ions in the unit cell having a space group of P-3m1. Further enthalpy and
phonon calculations support the existence of this phase, which stabilizes in a narrow pressure range of 2.8 – 3.6 GPa at zero
temperature. Upon further compression, transitions to denser packed phases of β-and γ-Li3N are typical first order. The analysis of the electronic densities of states suggests that all the high pressure modifications
of Li3N are insulators and, interestingly, the typical behavior of compression is to broaden the band gap. 相似文献
8.
J. Kurpeta A. Andreyev J. Äystö A.-H. Evensen M. Huhta M. Huyse A. Jokinen M. Karny E. Kugler J. Lettry A. Nieminen A. Płochocki M. Ramdhane H.L. Ravn K. Rykaczewski J. Szerypo P. Van Duppen G. Walter A. Wöhr 《The European Physical Journal A - Hadrons and Nuclei》2000,7(1):49-54
The decay of the neutron–rich isotope 216Bi, produced by proton–induced spallation at the PS Booster–ISOLDE facility, was investigated by β-γγ, αγ coincidence and
spectrum-multiscaling measurements. A new method for reducing isobaric contamination enabled to cover the unknown region “east”
of 208Pb for the isobaric chain A=216. The half-life of the β decay of 216Bi was found as T1/2= 135 ± 5 s. Its decay scheme was extended and the possible shell model configurations are proposed.
Received: 13 July 1999 / Revised version: 22 September 1999 相似文献
9.
L. I. Yakovenkova L. E. Kar’kina O. A. Elkina 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(5):650-652
An electron microscopic analysis of the dislocation structure of two-phase α2/β Ti-21.4 at % Al-5.6 at % Nb alloy deformed at ambient temperature was performed. It was established that after deformation,
the microstructure of the α2 phase consists of mobile a-superdislocations in the basal and prism planes and of 2c + a-superdislocations in the pyramidal planes. Some dislocations with the Burgers vector [0001] in the prism planes were also
observed. Deformation transfer from the α2 to the β phase occurs only due to a-super-dislocations with a Burgers vector corresponding to the Burgers orientation relations between these phases. The reasons
for the increase in plasticity in two-phase Ti3Al with Nb alloys are discussed. 相似文献
10.
A differential thermal analysis in vacuum and studies of the coefficients of electrical conductivity and thermal conductivity,
and of the thermal emf are made in Ag2Te in the neighborhood of the structural phase transition. It is shown that these data can be used to calculate the switching
factor L(T), determine the region in which the phases coexist within the transition, and calculate the thermodynamic parameters. Prior
to and after the main phase transition, additional displacement transitions are observed. It is found that the phase transition
takes place roughly according to the scheme α
385 K→α′405 K→β′420 K→β
440 K. The specific heat C
p, changes in entropy ΔS and transition enthalpy ΔH, as well as the minimum phase fluctuation volume V, and the heat Q of the phase transition are determined. It is shown that excesses of Te and Ag have almost no effect on the transition temperatures
T
0, but have a substantial effect on the thermodynamic parameters.
Fiz. Tverd. Tela (St. Petersburg) 40, 1693–1697 (September 1998) 相似文献
11.
K. P. Meletov A. V. Kuzmin R. P. Shibaeva 《Journal of Experimental and Theoretical Physics》2020,130(1):69-75
The Raman scattering spectra and crystalline structure of vanadyl IV phthalocyanine (VOPc) at normal and high pressures has been studied. According to the X-ray diffraction data, the initial microcrystalline powder represented a mixture of the triclinic α phase (79%) and the monoclinic β phase (21%) possessing P$$\bar {1}$$ and P21/c symmetry, respectively. Raman spectra of the two phases are similar, but the phonon modes of the β phase are shifted toward higher frequencies (energies). The pressure dependence of the spectra of the α phase has been determined and it is established that the interval of 2.3–3.4 GPa reveals reversible pressure-dependent variations: above 3 GPa, some phonon modes exhibit splitting and the coefficients of pressure-induced (baric) shift for almost all modes show a decrease. A high-pressure feature observed in the Raman spectra can be related to changes in intermolecular interactions in crystalline structure of the α phase. The pressure dependence of the α phase unit cell volume measured at pressures increasing up to 4 GPa is a smooth monotonic function that can be well described by the Murnaghan equation of state. The obtained data were used to calculate the Grüneisen parameters of VOPc phonon modes. 相似文献
12.
Comparison of the electro-optic coefficient r33 in well-defined phases of proton exchanged LiNbO3 waveguides 总被引:1,自引:0,他引:1
A. Méndez G. de la Paliza A. García-Cabañes J.M. Cabrera 《Applied physics. B, Lasers and optics》2001,73(5-6):485-488
The electro-optic coefficient, r33, of proton exchanged LiNbO3 waveguides has been measured in well-defined phases of the exchanged layer. Namely, in two low index-jump α-phases, i.e.
unannealed soft-exchanged (SPE) and annealed (APE) guides, and in two high index-jump phases, i.e. β1 guides and, for comparison, ordinary proton exchanged (PE) guides (having a mixture of phases). The following values have
been obtained (in pm/V): 22.1±0.6 for SPE; 20.9±0.7 for APE; 0.33±0.01 for β1; and 0.76±0.04 for PE. Differences between these values are discussed in terms of the structure of the phase involved.
Received: 18 May 2001 / Revised version: 22 August 2001 / Published online: 30 October 2001 相似文献
13.
Z.Y. Chen J.P. Zhao T. Yano T. Ooie 《Applied Physics A: Materials Science & Processing》2002,75(2):213-216
Raman characteristics of carbon nitride films synthesized by nitrogen-ion-beam-assisted pulsed laser deposition were investigated.
In addition to the D (disorder) band and G (graphitic) band commonly observed in carbon nitride films, two Raman bands located
at 1080–1100 and 1465–1480 cm-1 were found from our carbon nitride films. These two bands were well matched with the predicted Raman frequencies for βC3N4 and the observed Raman bands reported for carbon nitride films, indicating their relation to carbon-nitrogen stretching vibrations.
Furthermore, the relative intensity ratio of the two Raman bands to the D and G bands increased linearly with increasing nitrogen
content of the carbon nitride films.
Received: 30 October 2000 / Accepted: 5 February 2001 / Published online: 2 October 2001 相似文献
14.
T. Matsuzaki K. Nagamine K. Ishida N. Kawamura S. N. Nakamura M. Kato H. Sugai M. Tanase K. Kudo N. Takeda G. H. Eaton 《Hyperfine Interactions》2001,138(1-4):295-305
We have measured X-rays and neutrons associated with the muon catalyzed t–t fusion process at the RIKEN-RAL Muon facility.
In the X-ray measurement, we observed Kα and Kβ X-rays originating from the muon sticking process in muon catalyzed t–t fusion, and obtained the Kα X-ray yield and the Kβ/Kα intensity ratio. An average recoil energy of the (μ−α) atoms in a solid T2 medium was determined from the observed Doppler broadening width of the Kα X-ray line. The obtained t–t fusion neutron has shown an exponential time spectrum with a single component and a continuous
energy spectrum with a maximum energy of 9 MeV. We have determined the t–t fusion neutron yield, the t–t fusion cycling rate
and the muon sticking probability from the neutron data. The obtained maximum neutron energy is a very peculiar value from
the view point of the reaction Q value (11.33 MeV) with the three-particle decay mode at the exit channel: t + t → α + n + n + Q. The obtained neutron energy distribution was analyzed by a simple model with two neutron energy components; reasonable agreement
has been obtained, suggesting a strong (n–α) correlation in the exit channel of the t–t muon catalyzed fusion reaction.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
J. Mrázek M. Honusek A. Špalek J. Bielčík J. Slívová J. Adam A.A. Pasternak 《The European Physical Journal A - Hadrons and Nuclei》1999,5(4):399-408
The results of in-beam investigations of excited states of 99Ru using the 98Mo(α,3n) reaction are presented. Angular distributions of γ–rays and γ–γ coincidences have been measured. Excited states have
been identified up to an energy of E = 5603 keV and spin of Iπ= 31/2−. Mean lifetimes τ have been determined using the DSA method for eleven levels. Aligned angular momenta are discussed and
the probable (νh
11/2) origin of a backbending at frequency about 0.5 MeV was confirmed. The possible role of (νd
5/2) alignment at frequencies above 0.5 MeV was pointed out.
Received: 13 January 1999 / Revised version: 26 March 1999 相似文献
16.
This paper presents an exhaustive study of the Li-Zn-P system through the synthesis and electrochemical characterisation of
several binary and ternary phases: Li9ZnP4, LiZnP, Zn3P2 (α and β), ZnP2 (α and β), LiZn, and LiZn4. Three synthetic routes have been used to prepare these materials: ceramic synthesis and ball milling without and with annealing.
Li-Zn-P system phases have been evaluated through X-ray diffraction and electrochemical reactivity towards lithium. Exhibiting
high specific capacities at potentials close to 0.7 V vs. Li+/Li, some of these materials are promising as negative electrode materials for lithium ion battery.
Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 – 18, 2004. 相似文献
17.
V. Aravindan P. Vickraman A. Sivashanmugam R. Thirunakaran S. Gopukumar 《Applied Physics A: Materials Science & Processing》2009,97(4):811-819
Polyvinylidenefluoride–hexafluoropropylene-based (PVdF–HFP-based) gel and composite microporous membranes (GPMs and CPMs)
were prepared by phase-inversion technique in the presence 10 wt% of AlO(OH)
n
nanoparticles. The prepared membranes were gelled with 0.5-M LiPF3(CF2CF3)3 (lithium fluoroalkylphosphate, LiFAP) in EC:DEC (1:1 v/v) and subjected to various characterizations; the AC impedance study
shows that CPMs exhibit higher conductivity than GPMs. Mechanical stability measurements on these systems reveal that CPMs
exhibit Young’s modulus higher than that of bare and GPMs and addition of nanoparticles drastically improves the elongation
break was also noted. Transition of the host from α to β phase after the loading of nanosized filler was confirmed by XRD and Raman studies. Physico-chemical properties, like liquid
uptake, porosity, surface area, and activation energy, of the membranes were calculated and results are summarized. Cycling
performance of Li/CPM/LiFePO4 coin cell was fabricated and evaluated at C/10 rate and delivered a discharge capacity of 157 and 148 mAh g−1 respectively for first and tenth cycles. 相似文献
18.
A variational approach is developed for bound state calculations in three- and four-electron atomic systems. This approach
can be applied to determine, in principle, an arbitrary bound state in three- and four-electron ions and atoms. Our variational
wave functions are constructed from four- and five-body Gaussoids that respectively depend on six (r
12, r
13, r
14, r
23, r
24, r
34) and ten (r
12, r
13, r
14, r
15, r
23, r
24, r
25, r
34, r
35 and r
45) relative coordinates. The approach allows operating with the more than one electron spin functions. In particular, the trial
wave functions for the 1
S states in four-electron atomic systems include the two independent spin functions χ1 = αβαβ + βαβα − βααβ − αββα and χ2 = 2ααββ + 2ββαα − βααβ − αββα − βαβα − αβαβ. We also discuss the construction of variational wave functions for the excited
23
S states in four- electron atomic systems. 相似文献
19.
K. Wang H. Lee R. Cooper H. Liang 《Applied Physics A: Materials Science & Processing》2009,95(2):435-441
We investigate the time-dependent and anisotropic phase transformation of poly (vinylidene difluoride) (PVDF) under bending.
Using combined techniques of an atomic force microscope and a Fourier transform infrared spectroscope, observation of surface
morphology and phase transformation in time was made. Results showed that bending stress induces the transformation of amorphous,
α,β, and γ crystalline phases. Specifically, the amorphous phase was transformed into the β phase when the bending force was applied. In addition, the transformation observed was time and direction dependent. The
anisotropic behavior observed brings insights into the origin of the piezoelectricity of PVDF. 相似文献
20.
This paper reports the heterogeneously doped alumina (Al2O3) on the ionic conductivity of thallium iodide. Composite materials of formula (1 − x) TlI–xAl2O3, x = 0–0.7 have been prepared and studied by X-ray diffraction, differential scanning calorimetry, and electrical conductivity.
X-ray diffraction and differential scanning calorimetry proved the formation of composite in this binary system. The maximum
enhancement observed is about three orders of magnitude with respect to the host material. The enhancement of electrical conductivity
in comparison with pure thallium iodide can be interpreted with the space charge layer model. Moreover, the increased content
of alumina in the system leads to the disappearance of phase transition β–α thallium iodide, which is usually observed in
the pure compound. This behavior was explained by stabilizing effect of β-phase at high temperatures and suppression of α-phase
at higher contents of alumina. 相似文献