共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Szerypo H.U. Friebel D. Frischke R. Grossmann H.J. Maier 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2008,590(1-3):73
Production of HgS targets, based on HgO, is described. The HgS is precipitated from HgO dissolved in diluted HNO3 by gaseous H2S. Subsequently the target is manufactured by evaporation–condensation of HgS in vacuum. This way the 204HgS layers of 500 μg/cm2 on a backing carbon foil of 26 μg/cm2 were produced. 相似文献
2.
H. Sakata T. Kikuchi H. H. Qiu H. Shimizu M. Amano 《Journal of Materials Science: Materials in Electronics》1999,10(9):643-648
Amorphous films of the V2O5-CaO-MoO3 system are fabricated by r.f.-sputtering and the d.c. conductivity and optical properties are studied. The conductivity of 1200–1400 nm thick amorphous V2O5-CaO-MoO3 films with different film compositions ranges from 4.7 × 10–4 to 1.1 S cm–1 at 458 K. The films are n-type semiconducting. The conduction of the films is attributed to adiabatic small polaron hopping and is primarily due to hopping between V4+ and V5+ ions. The films are optically transparent in the visible range. The optical band gap energy is evaluated to be between 2.90 and 2.39 eV. The Urbach tail analysis gives the width of localized states between 0.40 and 0.58 eV. A feasibility study reveals the films to be applicable as transparent film thermistors. 相似文献
3.
Fluorescence and nonlinear optical properties of non-aggregating hexadeca-substituted phthalocyanine
Hacene Manaa Abdullah Al Mulla Saad Makhseed Moyyad Al-sawah Jacob Samuel 《Optical Materials》2009,32(1):108-114
Highly non-aggregating hexadeca-substituted phthalocyanine (Pc) complexes were prepared and their fluorescence and nonlinear optical properties were studied. Three visible fluorescence bands were observed when the Pc complexes were excited at 355 nm and found to be concentration dependent. They are attributed to the optical transitions S2 → S0 at 415 nm, T2 → T1 at 630 nm, and S2 → S1 at 755 nm. Nonlinear absorptive and refractive effects were measured with the help of Z-scan technique. Saturation absorption was observed at 632.8 nm where the nonlinear absorption coefficient is found to be very large (β = −2.8 × 10−2 cm/W) and the refractive nonlinear coefficient γ = −9.5 × 10−11 cm2/W. In the transparency domain at 532 nm, reverse absorption saturation is observed and β and γ are found to be 17.5 and 15.5 times smaller, respectively. Optical limiting performances are measured in the absorption and transparency domains. Purely refractive-based optical limiting at 632.8 nm is found to have a threshold of 0.16 kW/cm2, lower than the reverse absorption saturation and refractive-based optical limiting of 0.90 kW/cm2 at 532 nm. 相似文献
4.
K. R. Murali 《Journal of Materials Science》2003,38(18):3845-3849
CdSe
x
Te1 – x
films have been deposited by the brush plating technique for the first time, on titanium and conducting glass substrates at room temperature. These films were annealed in argon atmosphere at 475°C for 15 min. Their structural, optical and photoelectrochemical (PEC) properties are presented and discussed. The power conversion efficiency has been found to be 9.0% at 60 mW cm–2white light illumination. A peak quantum efficiency of 0.7 has been obtained for the films of composition CdSe0.7Te0.3. Donor concentration of 1017cm–3and electron mobility of 60 cm2V–1sec–1were obtained. 相似文献
5.
Vijay Singh R.P.S. Chakradhar J.L. Rao Jun-Jie Zhu 《Materials Chemistry and Physics》2008,111(1):143-148
Red-emitting BaAl2O4:Cr3+ phosphor material is prepared by urea combustion route in 5 min. Powder X-ray (XRD) diffraction, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and BET surface area measurements are used to characterize the as-prepared combustion products. Electron Paramagnetic Resonance (EPR) studies have been carried out on Cr3+ ions in BaAl2O4 phosphors at room temperature and at 110 K. The number of spins participating in resonance (N) and its paramagnetic susceptibilities (χ) have also been evaluated. The excitation spectra shows two broad and intense bands corresponding to Cr3+ ion in octahedral symmetry. The red emission peak observed at 705 nm is identified as due to 2Eg → 4A2g transition from Cr3+ ions. The crystal field parameter Dq and Racah inter-electronic repulsion parameters B and C have been evaluated. From the results and analyses of the EPR and optical studies, the site symmetry of Cr3+ ion in this phosphor is attributed to a distorted octahedron. 相似文献
6.
Xiaoxia Zhao Xiaojun Wang Baojiu Chen Qingyu Meng Bin Yan Weihua Di 《Optical Materials》2007,29(12):1680-1684
A novel red emitting phosphor α-Gd2(MoO4)3:Eu3+ was developed for white light emitting diodes (LEDs). The phosphor was prepared by solid-state reaction. The effects of the flux content and the activator concentration on the crystal structure, morphology and luminescent properties were investigated by using XRD, SEM, and fluorescent spectra. These results showed that this phosphor can be effectively excited by ultraviolet (UV) (395 nm) and blue (465 nm) light, matching the output wavelengths of ultraviolet or blue LED chips. The α-Gd2 (MoO4)3 phosphor may be a better candidate for solid state lighting application. 相似文献
7.
Jiang Li Zhenrong Sun Xiaorong Zhu Heping Zeng Zhizhan Xu Zugeng Wang Jian Lin Wenhai Huang Robert S. Armstrong Peter A. Lay 《Optical Materials》2004,25(4):401-405
We examined the optical nonlinear properties of ZnO–Nb2O5–TeO2. The absorption and Raman spectra were measured, the third-order nonlinear susceptibility was determined by degenerated four wave mixing technique. The magnitude of χ(3) is about 1.0 × 10−12 esu, larger than that of silica glasses, and the optical bistability was observed in a Fabry–Perot cavity. 相似文献
8.
The experimental results on the physical and hydrophobic properties of the ambient pressure dried silica aerogels as a function of sol-gel and drying conditions, are reported.The aerogels have been produced by a two stage (acidic and basic) catalytic sol-gel process using tetraethylorthosilicate (TEOS) precursor, oxalic acid (OXA) and ammonium hydroxide (NH4OH) catalysts, ethanol (EtOH) solvent and hexamethyldisilazane (HMDZ) silylating agent at 200∘C.The molar ratios of HMDZ/TEOS (M), OXA/TEOS (A) NH4OH/TEOS (B), acidic H2O/TEOS (Wa) basic H2O/TEOS (Wb), EtOH/TEOS (S) were varied from 0.09 to 0.9, 3.115 × 10− 5 to 3.115 × 10−3, 4 × 10− 3 to 8 × 10− 2, 2 to 9, 1.25 to 5 and 1 to 16 respectively. The physical properties such as the percentage (%) of volume shrinkage, density, thermal conductivity, percentage of porosity, the percentage of optical transmission and contact angle have been found to be strongly dependent on the sol-gel parameters. It was found from the FTIR spectra of the aerogels that with the increase of M, the bands at 3500 and 1600 cm− 1 corresponding to H-OH and Si-OH respectively decreased and the bands at 840 and 1250 cm− 1 due to Si-C and 2900 and 1450 cm−1 due to C-H increased. The best quality silica aerogels in terms of low density, low volume shrinkage, low thermal conductivity, high hydrophobicity and high optical transmission have been obtained with the molar ratio of TEOS:EtOH:acidicH2O:basicH2O:OXA:NH4OH:HMDZ at 1:8:3.75:2.25:6.23 × 10− 5: 4 × 10− 2:0.36 respectively, by ambient pressure dried method. 相似文献
9.
Xiangling Ren Xianwei Meng Fangqiong Tang Lin Zhang 《Materials science & engineering. C, Materials for biological applications》2009,29(7):2234-2238
In this paper, glucose biosensor is fabricated with immobilization of glucose oxidase (GOx) in platinum and silica sol. The glucose biosensor combined with Pt and SiO2 nanoparticles could make full use of the properties of nanoparticles. A set of experimental results indicates that the current response for the enzyme electrode containing platinum and silica nanoparticles increases from 0.32 µA cm− 2 to 33 µA cm− 2 in the solution of 10 mM β-D-glucose. The linear range is 3 × 10− 5 to 3.8 × 10− 3 M with a detection limit of 2 × 10− 5 M at 3σ. The effects of the various volume ratios of Pt and SiO2 sols with respect to the current response and the stability of the enzyme electrodes are studied. 相似文献
10.
K. K. Maurya Neelam Srivastava S. A. Hashmi S. Chandra 《Journal of Materials Science》1992,27(23):6357-6364
A new proton conducting polymer electrolyte PEO + NH4l system has been investigated. The solution-cast films of different stochiometric ratios have been prepared and characterized. Proton transport has been established using various experimental studies, namely optical microscopy, X-ray diffraction, differential thermal analysis, infrared, coulometry transient ionic current and electrical conductivity measurements at different temperatures and humidity. The maximum conductivity of the complexed material has been found to be 10–5 S cm–1. Both H+ ion and I– anion movements are involved with respective transference numbers and mobilities ast
H+=0.74, ,t
l–=0.09, H+=4.97 × 10–6 cm2 V–1 s–1 and l–=7.65. 相似文献
11.
This work focuses on the development of Eu2+-doped strontium (Sr)-borate as a yellow-emitting phosphor and its application to the fabrication of white light-emitting diodes (LEDs). Synthesis of Eu2+-doped Sr-borate phosphors was finely tuned for obtaining the efficient yellow luminescence through varying host composition, Eu concentration, and firing temperature. The 1300 °C-fired Eu2+-doped Sr3B2O6, which was found to be the most efficient candidate to date, was used for white LED fabrication. Their optical properties were evaluated, resulting in warm white lights with CIE chromaticity coordinates of (0.340–0.372, 0.287–0.314) and color rendering indices of 75–77 under the forward currents of 5–40 mA. 相似文献
12.
Undoped and Eu3+-doped CaF2–SiO2 gels were prepared by the sol–gel method and their optical properties have been studied. The UV–VIS–NIR absorption and photoluminescence spectra have shown the bands typical for the Eu3+ ions transitions. When the Eu-doped gel is annealed at temperatures up to 800 °C (i.e. above the CaF2 crystallisation peak at 460 °C) the photoluminescence spectra intensity increase, the 590 nm (5D0→7F1) and 620 nm (5D0→7F2) luminescence bands become comparable and a structuring of the 620 nm band is observed. The phonon sidebands peaks associated with the 5F0→7D2 transition of the Eu3+ ion were observed at around 1000 and 620 cm−1 and have been assigned to the Si–O and Ca–O bonds, respectively. A phonon sideband signal in the range of 300–400 cm−1 was attributed to Ca–F bonds in the precipitated CaF2 phase. From the optical absorption, photoluminescence and phonon sidebands spectra we have concluded that in the gels annealed at 800 °C, the Eu3+ ions are incorporated into the silica network and in the precipitated CaF2 phase. 相似文献
13.
M. M. Elkholy Z. I. El-Badawy A. A. El-Adawy L. M. Sharaf El-Deen 《Journal of Materials Science: Materials in Electronics》1995,6(6):409-414
Infrared absorption spectra were measured in the spectral range 4000–200 cm–1 for the Cu2O-Bi2O3 glass system. Strong bands were observed around 436–477, 600–632, 700–715, 810–875, 975–1000, 1550–1610 and 3225–3510 cm–1 which are due to harmonics of the Bi-O-Bi stretching vibration, Cu-O stretching vibrations, O-Bi-O stretching vibrations, O-Bi-O bending vibrations, Bi-O stretching vibrations, free H2O normal-mode bending vibrations and free H2O molecules or OH– ions, respectively. Quantitative justification of these absorption bands shows that the values of the experimental wave number for most recorded absorption bands agree well with the theoretical ones.The optical absorption spectra were recorded for the same glass system in the spectral range 300–700 Nm. These records show that the absorption edge has a tail extending towards lower energies. The edge shifts towards lower energies with increasing Cu2O content. This shift is mostly related to the structural rearrangement and the relative concentrations of the glass basic units. By increasing the Cu2O content, the optical energy gap decreases, while the width of the localized states increases. 相似文献
14.
Brian Dickens Sabine H. Dickens 《Journal of research of the National Institute of Standards and Technology》1999,104(2):173-183
Integrated near infrared (NIR) absorbance has been used to determine the absorptivity of the υ2 + υ3 combination band of the asymmetric stretch (υ2) and the bending vibration (υ3) for water in several organic solvents. Absorptivity measured in this way is essentially constant across the absorption envelope and is found to be 336 L mol−1 cm−1 with a standard deviation of 4 L mol−1 cm−1 as estimated from a least squares fit of a straight line to data from water concentrations between 0.01 mol/L and 0.06 mol/L. Absorptivity measured from the peak maximum of the υ2 + υ3 combination band of water varies with the type of hydrogen bonding of the water molecule because the shape of the NIR absorption envelope changes with the hydrogen bonding.Because the integrated NIR absorptivity of the υ2 + υ3 combination band of water is essentially constant across the absorption envelope, the NIR absorption envelope reflects the distribution of hydrogen bonding of the water. The shape and location of the absorption envelope appear to be governed mostly by the number of hydrogen bonds from the water molecules to easily polarized atoms. Water that is a donor in hydrogen bonds to atoms which are not easily polarized (such as the oxygen of a typical carbonyl group) absorbs near 5240 cm−1 to 5260 cm−1. Water that donates one hydrogen bond to an easily polarized atom (such as a water molecule oxygen) absorbs near 5130 cm−1 to 5175 cm−1, and water that donates two hydrogen bonds to easily polarized atoms is estimated to absorb near 5000 cm−1 to 5020 cm−1. Water donating two hydrogen bonds to other water molecules may be said to be in a water-like environment. In no case does a small amount of water absorbed in a host material appear to have a water-like environment. 相似文献
15.
The optical properties of intrinsic SnO2 (TO) and fluorine doped (FTO) are characterized in terms of the dielectric function ε(ħω) = ε1(ħω) + iε2(ħω) by electronic structure calculations. The intrinsic TO shows intriguing absorption characteristics in the 3.0–8.0 eV region: (i) the low energy region of the fundamental band gap (3.2 < ħω < 3.9 eV), the optical transitions Г3+ → Г1+ (valence-band maximum to conduction-band minimum) is symmetry forbidden, and the band-edge absorption is therefore extremely weak. (ii) In the higher energy region (3.9 < ħω < 5.1 eV) the Г5− → Г1+ transitions (from the second uppermost valence band) is strongly polarized perpendicular to the main c axis. (iii) Transitions with polarization axis parallel to c axis are generated from Г2− → Г1+ transitions (from the third uppermost valence bands), and dominates at high energies (5.1 < ħω eV). Heavily F doped TO (FTO) with doping concentrations nF = 4 × 1020 cm− 3 changes the absorption significantly: (iv) Substitutional FO generates strong inter-conduction band absorption at 0.8, 2.2, and 3.8 eV which affects also the high frequency dielectric constant ε∞. (v) Interstitial Fi is inactive as a single dopant, but act as a compensating acceptor in highly n-type FTO. This explains the measured non-linear dependence of the resistivity with respect to F concentration. 相似文献
16.
This paper reports the structural, optical and luminescence properties of Yb3+/Er3+ codoped Y2O3 phosphor synthesized by combustion method. The prepared phosphor was characterized by X-ray diffraction (XRD). XRD studies confirm the body-centered cubic structure of the phosphor. The optical properties such as diffuse reflectance (DR), photoluminescence and thermoluminescence were studied. DR spectra were used to determine the bandgap of the phosphor. Mechanism of upconversion by two-photon and energy transfer processes are interpreted and explained. The color coordinates were measured and the color tunability was analyzed as a function of the 980 nm excitation source power. Different trapping parameters associated with the glow peak were calculated by various glow curve methods. 相似文献
17.
Photothermal deflection is among the most sensitive techniques available for the measurement of small, localized heating, such as that from the absorption of a focused laser beam in the bulk or surface of a material. A thin optical probe beam is deflected by the refractive-index gradients arising from the heating, and the size of the deflection provides the measure of the heating. We describe the use of a critical fluid to enhance the sensitivity of the technique by at least 103. The diverging coefficient of thermal expansion of a pure fluid near the gas-liquid critical point gives this dramatic enhancement when used as a sensing fluid. With sensitivity calculations and measurements in supercritical xenon,T
c16.7C, we show that the noise floor of our apparatus when used for surface absorption measurements corresponds to a fractional power absorbed ofP
absorbed/P
incident=10–10, while the noise floor for bulk measurements corresponds to an absorption coefficient=10–13 cm–1. We report the first measurements of the surface absorption of superpolished surfaces of sapphire and fused quartz,P
a/P
i2×10–5, and the first measurements of the bulk absorption in xenon,2×10–6 cm–1. We also show how the present work fits into the current status of absorption measurement techniques and describe the effects of the peculiar properties of critical fluids on the execution of photothermal deflection measurements. 相似文献
18.
SrAl2O4:Eu2+ phosphor was prepared by a solid-state reaction in CO-reductive atmosphere. X-ray powder diffraction (XRD) analysis confirmed the formation of SrAl2O4:Eu2+. Field-emission scanning electron-microscopy (FE-SEM) observation indicated that the microstructure of the phosphor consisted of irregular fine grains with an average size of about 7–8 μm. Photoluminescence measurements showed that the phosphor can be efficiently excited by UV–visible light from 350 to 430 nm, and exhibited bright green emission peaked at about 516 nm. Bright green LEDs were fabricated by incorporating the phosphor with an InGaN-based UV chip. All the characteristics indicated that SrAl2O4:Eu2+ is a good candidate phosphor applied in white LEDs. 相似文献
19.
Ronald G. Munro 《Journal of research of the National Institute of Standards and Technology》2000,105(5):709-720
The physical, mechanical, and thermal properties of polycrystalline TiB2 are examined with an emphasis on the significant dependence of the properties on the density and grain size of the material specimens. Using trend analysis, property relations, and interpolation methods, a coherent set of trend values for the properties of polycrystalline TiB2 is determined for a mass fraction of TiB2 ⩾ 98 %, a density of (4.5±0.1) g/cm3, and a mean grain size of (9±1) µm. 相似文献
20.
A series of CuCr1 − xNixO2 (0 ≤ x ≤ 0.06) polycrystalline samples was prepared. The electrical conductivity was measured in the temperature range of 160–300 K. It was found that the electrical conductivity (σ) increases rapidly with the doping of Ni2+ ions. At room temperature, the σ is 0.047 S cm− 1 for the sample with x = 0.06, which is two orders of magnitude larger than that of the CuCrO2 sample (9.49E− 4 S cm− 1). The Seebeck coefficients are positive for all samples, which indicate p-type conducting of the samples. The experimental results imply that it is possible to get higher electrical conductivity p-type transparent conducting oxides (TCO) from CuMO2 by doping with divalent ions. 相似文献