共查询到20条相似文献,搜索用时 562 毫秒
1.
S. Banerjee K. Miyata K. Kato N. Saito S. Wada 《Applied physics. B, Lasers and optics》2007,87(1):101-103
AgGa1-xInxS2 with x=0.14±0.01 was found to be 90° phase-matchable for type-I difference-frequency generation (DFG) by mixing the dual-wavelength
pulses emitted from an electronically tuned Ti:sapphire laser. Infrared radiation continuously tunable over the range of 4.80–6.98 μm
was generated by independently varying the two wavelengths in the 705–932 nm spectral range, and 4.04 μm radiation by mixing
a Nd:YAG laser with the Ti:sapphire laser. In addition, this material was found to be noncritically phase-matchable for the
second harmonic generation (SHG) of CO2 laser radiation at 10.591 μm at 203 °C. Sellmeier equations that reproduce well these experimental data are presented.
PACS 42.65.-k; 42.65.ky 相似文献
2.
We present a Sellmeier equation that describes the refractive index dispersion of congruently grown LiTaO3, accurate from 0.3 to 5 μm and from 23 to above 200°C. Data were acquired by two different ways: directly by the minimal
deviation technique in the visible and near-infrared range and indirectly by quasi-phase-matched optical parametric generation
in PPLT in the mid-infrared range. The data was fit to a Sellmeier equation based on two oscillators in the UV and an infrared
correction. The resulting equation accurately predicts the tuning curves for optical parametric generation in the infrared,
as well as the correct quasi-phase-matching conditions for frequency conversion into the ultraviolet by second-harmonic generation. 相似文献
3.
The electrophysical properties and structure of the nonstoichiometric high-temperature superconductor YBa2Cu3O
y
restored at T = 930–950°C after low-temperature decomposition (T = 200°C) into phases different in the oxygen content have been studied. It has been shown that, unlike heat treatments at
T ≤ 900°C, the superconducting properties are almost completely restored for 3–5 h during grain recrystallization, which is
impossible at lower temperatures. After short-term annealing at T = 930–950°C (for 1–2 h), the ceramic material still contains a significant number of structural defects, most likely, in
cation sublattices. These defects can contribute to the pinning of magnetic vortices, which substantially increases the critical
current density in magnetic fields up to 2 T as compared to ceramic materials produced by the conventional technology. 相似文献
4.
A. V. Semirov D. A. Bukreev A. A. Moiseev V. A. Lukshina E. G. Volkova S. O. Volchkov G. V. Kurlyandskaya 《Technical Physics》2011,56(3):395-399
The temperature dependences of the magnetic properties and the magnetoimpedance effect of soft magnetic nanocrystalline Fe73.5Si16.5B6Nb3Cu1 alloy ribbons are studied in the temperature range 24–160°C. A high temperature sensitivity of the impedance and the magnetoimpedance
effect of the ribbons are detected in the ac frequency range 0.1–50 MHz. At an ac frequency of 50 MHz, the change in the impedance
reaches 0.2 Ω/°C (0.5%/°C) in the temperature range 85–160°C. When the temperature increases, a monotonically decreasing character
of the dependence of the magnetoimpedance effect on the applied magnetic field changes into a dependence having an increasing
initial segment. The effect of temperature on the magnetoimpedance properties of the soft magnetic nanocrystalline ribbons
is shown to result from temperature-induced changes in their electrical conductivity, magnetization, and effective magnetic
anisotropy. 相似文献
5.
V. Singh S. Watanabe T. K. Gundu Rao I.-J. Lee 《Applied physics. B, Lasers and optics》2011,104(4):1019-1027
Tricalcium aluminate doped with Eu3+ was prepared at furnace temperatures as low as 500°C by using the convenient combustion route and examined using powder X-ray
diffraction, scanning electron microscope and photoluminescence techniques. A room-temperature photoluminescence study showed
that the phosphors can be efficiently excited by UV/Visible region, emitting a red light with a peak wavelength of 616 nm
corresponding to the 5D0–7F2 transition of Eu3+ ions. The phosphor exhibits three thermoluminescence (TL) peaks at 195°C, 325°C and 390°C. Electron Spin Resonance (ESR)
studies were carried out to study the defect centres induced in the phosphor by gamma irradiation and also to identify the
defect centres responsible for the TL process. Room-temperature ESR spectrum of irradiated phosphor appears to be a superposition
of three distinct centres. One of the centres (centre I) with principal g-value 2.0130 is identified as O− ion while centre II with an axially symmetric principal values g
∥=2.0030 and g
⊥=2.0072 is assigned to an F+ centre (singly ionized oxygen vacancy). O− ion (hole centre) correlates with the TL peak at 195°C and the F+ centre (electron centre), which acts as a recombination centre, is also correlated to the 195°C TL peak. F+ centre further appears to be related to the high temperature peak at 390°C. Centre III is also assigned to an F+ centre and seems to be the recombination centre for the TL peak at 325°C. 相似文献
6.
Zhe Zheng Yunzhong Chen Zexiang Shen Jan Ma Chorng-Haur Sow Wei Huang Ting Yu 《Applied Physics A: Materials Science & Processing》2007,89(1):115-119
We report the synthesis of single-crystalline α-Fe2O3 nanoflakes from a simple Fe–air reaction within the temperatures range of 260–400 °C. The nanoflakes synthesized at the lowest
temperature (260 °C) in this work show an ultra-sharp morphology: 5–10 nm in thickness, 1–2 μm in length, 20 nm in base-width
and around 5 nm at the tips; successfully demonstrate the promising electron field emission properties of a large-scaled α-Fe2O3 nanostructure film and exhibit the potential applications as future field-emission (FE) electron sources and displays (FEDs).
The formation and growth of α-Fe2O3 nanostructures were discussed based on the surface diffusion mechanism.
PACS 79.60.Jv; 79.70.+q; 77.84.Bw 相似文献
7.
C. Masingboon S. Maensiri T. Yamwong P.L. Anderson S. Seraphin 《Applied Physics A: Materials Science & Processing》2008,91(1):87-95
Nanocrystalline CaCu3Ti4O12 powders with particle sizes of 50–90 nm were synthesized by a simple method using Ca(NO3)2·4H2O, Cu(NO3)2·4H2O, titanium(diisoproproxide) bis(2,4-pentanedionate) and freshly extracted egg white (ovalbumin) in aqueous medium. The synthesized
precursor was characterized by TG-DTA to determine the thermal decomposition and crystallization temperature which was found
to be at above 400 °C. The precursor was calcined at 700 and 800 °C in air for 8 h to obtain nanocrystalline powders of CaCu3Ti4O12. The calcined CaCu3Ti4O12 powders were characterized by XRD, FTIR, SEM and TEM. Sintering of the powders was conducted in air at 1100 °C for 16 h.
The XRD results indicated that all sintered samples have a typical perovskite CaCu3Ti4O12 structure and a small amount of CuO, although the sintered sample of the 700 °C calcined powders contained some amount of
CaTiO3. SEM micrographs showed the average grain sizes of 12.0±7.8 and 15.5±8.9 μm for the sintered CaCu3Ti4O12 ceramics prepared using the CaCu3Ti4O12 powders calcined at 700 and 800 °C, respectively. The sintered samples exhibit a giant dielectric constant, ε′ of ∼ 1.5–5×104. The dielectric behavior of both samples exhibits Debye-like relaxation, and can be explained based on a Maxwell–Wagner model.
PACS 77.22.Gm; 81.05.Je; 81.07.Wx; 81.20.Ev 相似文献
8.
A. V. Semirov D. A. Bukreev V. O. Kudryavtsev A. A. Moiseev A. A. Gavrilyuk A. L. Semenov G. V. Zakharov 《Technical Physics》2009,54(11):1586-1590
The effect of temperature and elastic tensile stresses on the magnetoimpedance of an amorphous Vitrovac 6025Z (Fe4CO67Mo1.5Si16.5B11) foil is studied. Two temperature ranges (20–70 and 70–220°C) in which the effect of elastic tensile stresses on the magnetoimpedance
has different characters are detected. The existence of these two temperature ranges is shown to be caused by a change in
the sign of a magnetostriction constant at 70°C. 相似文献
9.
The recently discovered compound LiFeVO4 was prepared by solid-state reaction at 570 °C during a 7-h period. The X-ray diffraction pattern revealed an orthorhombic
crystal structure. Thermogravimetric measurements revealed a reversible mechanism which was attributed to absorption–desorption
of humidity. Impedance spectroscopy measurements were carried out at 25 °C steps in the temperature range from 25 to 500 °C
and equivalent circuits were drawn to fit the impedance measurement results at each temperature level. The elements of the
equivalent circuits were assigned to bulk, grain boundary, and along grain boundary conductivity. All three conduction mechanisms
were found to be humidity sensitive. Arrhenius plots were plotted for the bulk and grain boundary conductivity processes.
The activation energy for the bulk conductivity process was calculated to be 0.25 eV over the temperature range from 175 to
500 °C and the activation energy for the grain boundary conductivity process was calculated to be 0.41 eV from 300 to 500 °C
and 0.20 eV from 175 to 275 °C. An explanation for the existence of these two grain boundary activation energies is attempted.
The dependence of the material conductivity mechanisms on humidity suggests that LiFeVO4 could be used as a humidity sensor. 相似文献
10.
Yu. M. Shul’ga E. N. Kabachkov D. V. Matyushenko E. N. Kurkin I. A. Domashnev 《Technical Physics》2011,56(1):97-101
TiO2 nanopowder is produced by the low-temperature hydrolysis of TiCl4. The phase composition of the sample is found to form at a hydrolysis temperature of 30–38°C. Low-temperature annealing (up
to 440°C) increases the degree of crystallinity of the phases present in the sample (anatase, brookite) and only weakly affects
their ratio. At 500°C, the sample consists of three phases: rutile is detected apart from anatase and brookite. Brookite begins
to fail at 600°C; at 700°C, crystalline brookite fails completely. 相似文献
11.
O. M. Fedorova V. F. Balakirev Yu. V. Golikov 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(8):1153-1154
The solubility ranges of Er2O3 and Mn3O4 oxides and ErMn2O5 manganite in ErMnO3 ± δ are determined for the temperature range 900–1400°C. 相似文献
12.
Banarji Behera Pratibindhya Nayak Ram N. P. Choudhary 《Central European Journal of Physics》2008,6(2):289-295
A polycrystalline sample of KCa2Nb5O15 with tungsten bronze structure was prepared by a mixed oxide method at high temperature. A preliminary structural analysis
of the compound showed an orthorhombic crystal structure at room temperature. Surface morphology of the compound shows a uniform
grain distribution throughout the surface of the sample. Studies of temperature variation on dielectric response at various
frequencies show that the compound has a transition temperature well above the room temperature (i.e., 105°C), which was confirmed
by the polarization measurement. Electrical properties of the material have been studied using a complex impedance spectroscopy
(CIS) technique in a wide temperature (31–500°C) and frequency (102–106 Hz) range that showed only bulk contribution and non-Debye type relaxation processes in the material. The activation energy
of the compound (calculated from both the loss and modulus spectrum) is same, and hence the relaxation process may be attributed
to the same type of charge carriers. A possible ‘hopping’ mechanism for electrical transport processes in the system is evident
from the modulus analysis. A plot of dc conductivity (bulk) with temperature variation demonstrates that the compound exhibits
Arrhenius type of electrical conductivity.
相似文献
13.
Using a very simple and straightforward approach we derive the condition to be satisfied for achieving wavelength-insensitive broadband phase matching in a type-I noncollinear optical parametric amplifier (NOPA), required for the generation of ultra-fast laser radiation. Nonlinear optical properties of a relatively newly grown crystal Li2B4O7 (LB4) have also been studied and we found that this crystal satisfies the condition required to realize the broadband phase matching and is suited for the generation of tunable visible–near-infrared ultra-fast laser radiation employed in a 395-nm-pumped type-I NOPA. The phase-matching bandwidths of type-I NOPAs in different borate-group crystals, such as BBO, CLBO, and KABO, are also numerically estimated. The values are 157, 164, 152, and 174 THz for 1-mm-thick BBO, CLBO, KABO, and LB4 crystals, with the noncollinear angles between the input pump and the signal beams 3.7°, 3.0°, 3.4°, and 2.9°, respectively, for the signal wavelengths centered at 630 nm. In addition to the largest bandwidth, LB4 crystal has several other attractive properties to be used in optical parametric applications, such as high laser damage threshold, wide optical transmission, easy crystal growth to excellent optical quality with large sizes, easy treatment of cutting and polishing, and nonhygroscopicity. PACS 42.65.Yj; 42.65.Re; 42.70.Mp 相似文献
14.
R.G. Abhilash Kumar K. Vinod U. Syamaprasad 《Applied Physics A: Materials Science & Processing》2007,88(2):243-247
MgB2/Fe wires were prepared by electrical self-heating of in situ powder-in-tube wires for the first time at ambient conditions.
Characterization of the wires processed at 750 °C, 800 °C and 850 °C for 15 min by XRD, SEM, ϱ–T, susceptibility and JC measurements shows that the MgB2 formed is of high quality particularly with respect to phase purity and transport JC. The method considerably reduces the overall energy consumption vis-à-vis the production cost, simplifies the complexity
of the fabrication procedure and is promising for manufacture of high-quality MgB2 superconducting wires.
PACS 74.70.Ad; 74.62.Bf; 74.25.Fy; 74.25.Ha; 81.20.Hy 相似文献
15.
M.?Cristina?Gon?alves Verónica?de?Zea Bermudez M.?M.?Silva M.?J.?Smith Enrique?Morales Rute?A.?Sá Ferreira Luís?D.?Carlos 《Ionics》2010,16(3):193-201
Variable chain length di-urethane cross-linked poly(oxyethylene) (POE)/siloxane hybrid networks were prepared by application
of a sol-gel strategy. These materials, designated as di-urethanesils (represented as d-Ut(Y′), where Y′ indicates the average
molecular weight of the polymer segment), were doped with lithium triflate (LiCF3SO3). The two host hybrid matrices used, d-Ut(300) and d-Ut(600), incorporate POE chains with approximately 6 and 13 (OCH2CH2) repeat units, respectively. All the samples studied, with compositions ∞ > n ≥ 1 (where n is the molar ratio of (OCH2CH2) repeat units per Li+), are entirely amorphous. The di-urethanesils are thermally stable up to at least 200 °C. At room temperature the conductivity
maxima of the d-Ut(300)- and d-Ut(600)-based di-urethanesil families are located at n = 1 (approximately 2.0 × 10−6 and 7.4 × 10−5 Scm−1, respectively). At about 100 °C, both these samples also exhibit the highest conductivity of the two electrolyte systems
(approximately 1.6 × 10−4 and 1.0 × 10−3 Scm−1, respectively). The d-Ut(600)-based xerogel with n = 1 displays excellent redox stability. 相似文献
16.
J. C. Cruz V. Baglio S. Siracusano R. Ornelas L. Ortiz-Frade L. G. Arriaga V. Antonucci A. S. Aricò 《Journal of nanoparticle research》2011,13(4):1639-1646
Nanosized IrO2 electrocatalysts (d ~ 7–9 nm) with specific surface area up to 100 m2 g−1 were synthesized and characterized for the oxygen evolution reaction in a solid polymer electrolyte (SPE) electrolyzer. The
catalysts were prepared by a colloidal method in aqueous solution and a subsequent thermal treatment. An iridium hydroxide
hydrate precursor was obtained at ~100 °C, which was, successively, calcined at different temperatures from 200 to 500 °C.
The physico-chemical characterization was carried out by X-ray diffraction (XRD), thermogravimetry–differential scanning calorimetry
(TG–DSC) and transmission electron microscopy (TEM). IrO2 catalysts were sprayed onto a Nafion 115 membrane up to a loading of 3 mg cm−2. A Pt catalyst was used at the cathode compartment with a loading of 0.6 mg cm−2. The electrochemical activity for water electrolysis of the membrane-electrode assemblies (MEAs) was investigated in a single
cell SPE electrolyzer by steady-state polarization curves, impedance spectroscopy and chrono-amperometric measurements. A
maximum current density of 1.3 A cm−2 was obtained at 1.8 V and 80 °C for the IrO2 catalyst calcined at 400 °C for 1 h. A stable performance was recorded in single cell for this anode catalyst at 80 °C. The
suitable catalytic activity and stability of the most performing catalyst were interpreted in terms of proper combination
between nanostructure and suitable morphology. 相似文献
17.
The photovoltaic characteristics of a photoelectrochemical cell of ITO/TiO2/PVC-LiClO4/graphite are reported. This paper is concerned with the influence of light intensity and temperature on short-circuit current
density, Jsc and open-circuit voltage, Voc of the device. The photoelectrochemical cell material was a screen-printed layer of titanium dioxide onto an ITO-covered
glass substrate, which was used as a working electrode of the cell. The solid electrolyte was polivinylchloride-lithium perchlorate.
The graphite film serves as a counter electrode of the cell. The current density–voltage characteristics of the device under
an illumination of 20, 40, 60, 80 and 100 mW cm−2 light from a tungsten halogen lamp were recorded at 40 °C as well as under an illumination of 100 mW cm−2 at 30, 35, 40, 45 and 50 °C, respectively. It was found that the short-circuit current density, Jsc of the device increases with both light intensity and temperature. The Jsc obtained at 100 mW cm−2 was 1.0 μAcm−2 and that at 50 °C was 0.7 μAcm−2. 相似文献
18.
Fei Qi Anna Moiseev Joachim Deubener Alfred Weber 《Journal of nanoparticle research》2011,13(3):1325-1334
Anatase is the low-temperature (300–550 °C) crystalline polymorph of TiO2 and it transforms to rutile upon heating. For applications utilizing the photocatalytic properties of nanoscale anatase at
elevated temperatures (over 600 °C) the issue of phase stabilisation is of major interest. In this study, binary TiO2/SiO2 particles were synthesized by a flame aerosol process with TiCl4 and SiCl4 as precursors. The theoretical Si/Ti ratio was varied in the range of 0.7–1.3 mol/mol. The synthesized TiO2/SiO2 samples were heat treated at 900 and 1,000 °C for 3 h to determine the thermostability of anatase. Pyrogenic TiO2 P25 (from Evonik/Degussa, Germany) widely applied as photocatalyst was used as non-thermostabilized reference material for
comparison of photocatalytic activity of powders. Both the non-calcinated and calcinated powders were characterized by means
of XRD, TEM and BET. Photocatalytic activity was examined with dichloroacetic acid (DCA) chosen as a model compound. It was
found that SiO2 stabilized the material retarding the collapse of catalyst surface area during calcination. The weighted anatase content
of 85% remains completely unchanged even after calcination at 1,000 °C. The presence of SiO2 layer/bridge as spacer between TiO2 particles freezes the grain growth: the average crystallite size increased negligibly from 17 to 18 nm even during the calcination
at 1,000 °C. Due to the stabilizing effect of SiO2 the titania nanoparticles calcinated at 900 and 1,000 °C show significant photocatalytic activity. Furthermore, the increase
in photocatalytic activity with calcination temperature indicates that the titania surface becomes more accessible either
due to intensified cracking of the SiO2 layer or due to enhanced transport of SiO2 into the necks thus releasing additional titania surface. 相似文献
19.
D.S. Jung S.K. Hong J.S. Cho Y.C. Kang 《Applied Physics A: Materials Science & Processing》2007,89(3):769-774
Fine-sized BaO-ZnO-B2O3-SiO2 (BZBS) glass powders were directly prepared by high temperature spray pyrolysis. The hollow glass powders prepared at low
preparation temperature of 1000 °C had a low density of 2.65 g/cm3. However, the densities of the BZBS powders obtained at preparation temperatures of 1200 and 1400 °C were each 3.92 and 4.13 g/cm3. The mean size of the BZBS glass powders prepared by spray pyrolysis at preparation temperature of 1400 °C was 0.98 μm. The
glass transition temperature (Tg) of the prepared BZBS glass powders was 518.9 °C. The dielectric layers formed from the prepared BZBS glass powders with
a dense structure had a clean surface and a dense inner structure without voids at the firing temperature of 580 °C. The transparencies
of the dielectric layers formed from the prepared BZBS glass powders were higher than 90% within the visible range.
PACS 42.70.Ce; 85.60.Pg; 71.55.Jv 相似文献
20.
Elemental mixtures of Al, Cu, Fe powders with the nominal composition of Al70Cu20Fe10 were mechanically alloyed in a planetary ball mill for 80 h. Subsequent annealing of the as-milled powders were performed
at 600–800°C temperature range for 4 h. Structural characteristics of the mechanically alloyed Al70Cu20Fe10 powders with the milling time and the heat treatment were investigated by X-ray diffraction (XRD), differential scanning
calorimeter (DSC) and differential thermal analysis (DTA). Mechanical alloying of the Al70Cu20Fe10 did not result in the formation of icosahedral quasicrystalline phase (i-phase) and a long time milling resulted in the formation
of β-Al(Cu,Fe) solid solution phase (β-phase). The i-phase was observed only for short-time milled powders after heat treatment above 600°C. The β-phase was one of the major phases in the Al70Cu20Fe10 alloy. The w-Al7Cu2Fe1 phase (w-phase) was obtained only after heat treatment of the short-time milled and unmilled samples. The present investigation
indicated that a suitable technique to obtain a large amount of quasicrystalline powders is to use a combination of short-time
milling and subsequent annealing. 相似文献