共查询到20条相似文献,搜索用时 46 毫秒
1.
V.H. MudavakkatV.V. Atuchin V.N. KruchininA. Kayani C.V. Ramana 《Optical Materials》2012,34(5):893-900
Yttrium oxide (Y2O3) thin films were grown onto Si(1 0 0) substrates using reactive magnetron sputter-deposition at temperatures ranging from room temperature (RT) to 500 °C. The effect of growth temperature (Ts) on the growth behavior, microstructure and optical properties of Y2O3 films was investigated. The structural studies employing reflection high-energy electron diffraction RHEED indicate that the films grown at room temperature (RT) are amorphous while the films grown at Ts = 300-500 °C are nanocrystalline and crystallize in cubic structure. Grain-size (L) increases from ∼15 to 40 nm with increasing Ts. Spectroscopic ellipsometry measurements indicate that the size-effects and ultra-microstructure were significant on the optical constants and their dispersion profiles of Y2O3 films. A significant enhancement in the index of refraction (n) (from 2.03 to 2.25) is observed in well-defined Y2O3 nanocrystalline films compared to that of amorphous Y2O3. The observed changes in the optical constants were explained on the basis of increased packing density and crystallinity of the films with increasing Ts. The spectrophotometry analysis indicates the direct nature of the band gap (Eg) in Y2O3 films. Eg values vary in the range of 5.91-6.15 eV for Y2O3 films grown in the range of RT-500 °C, where the lower Eg values for films grown at lower temperature is attributed to incomplete oxidation and formation of chemical defects. A direct, linear relationship between microstructure and optical parameters found for Y2O3 films suggest that tuning optical properties for desired applications can be achieved by controlling the size and structure at the nanoscale dimensions. 相似文献
2.
Tb3Al5O12 transparent ceramics have been prepared by solid state reaction and vacuum sintering. The optical quality and the microstructure of the samples were investigated. The sample sintered at 1650 °C possessed relatively good optical transparency from 400 nm to 1600 nm. The Verdet constant measured at 632.8 nm of the quasi-pore-free Tb3Al5O12 transparent ceramic was −172.72 rad T−1 m−1, which was close to the counterpart of Tb3Al5O12 single crystal. The thermal conductivity of the sample was also measured. To the best of our knowledge, this is the first time that Tb3Al5O12 transparent ceramic with relatively good optical quality and magneto-optical property has been reported. 相似文献
3.
A novel method for preparing Al2O3/ZrO2 (Y2O3) eutectic was developed by combining combustion synthesis with melt-casting under ultra-high gravity (CSMC-UHG). The application of UHG = 800 g resulted in a high relative density of 99.8%, and an orientation-growth along the UHG direction. The microstructure was composed of aligned growth regimes containing a triangular dispersion of orderly ZrO2 rods in Al2O3 matrix with a spacing of 300 nm. The eutectic had a high fracture toughness up to 17.9 MPa·m1/2, which was mainly attributed to the nanostructure and the elastic bridge effects of the aligned ZrO2 rods. 相似文献
4.
Sue Jin KimHyung Il Won Nersisyan HaykChang Whan Won Duk Young JeonArtavazd G. Kirakosyan 《Materials Science and Engineering: B》2011,176(18):1521-1525
A new composition of red strontium aluminate phosphor (Sr4Al2O7:Eu3+, Eu2+) is synthesized using a solid state reaction method in air and in a reducing atmosphere. The investigation of firing temperature indicates that a single phase of Sr4Al2O7 is formed when the firing temperature is higher than 1300 °C and that a Sr3Al2O6 phase is formed as the main peak below 1300 °C. The effects of firing temperature and doping concentration on luminescent properties are investigated. Sr4Al2O7 phosphors exhibit the typical red luminescent properties of Eu3+ and Eu2+. A comparison photoluminescence study with Sr3Al2O6 phosphor shows that Sr4Al2O7 has higher emission intensity than Sr3Al2O6 as a result of the higher optimum doping concentration of Sr4Al2O7 phosphor. 相似文献
5.
A composite film of nanocrystalline Si (nc-Si) embedded in (Al2O3 + SiO2) has been prepared on a quartz substrate by thermally evaporating a 400 nm thick Al film on a quartz substrate and annealing in air at 580 °C for 1 h. During annealing, the Al reacts with the SiO2 of the quartz substrate and produces nc-Si, which is embedded in the (Al2O3 + SiO2) film. The average size of nc-Si is ~ 22 nm and the thickness of the nc-Si:(Al2O3 + SiO2) composite film is ~ 810 nm. It is found that the prepared film is thermoelectric with a Seebeck coefficient of − 624 μV/K at 293 K and − 225 μV/K at 413 K. 相似文献
6.
Degang DengShiqing Xu Xingyu SuQian Wang Yinqun LiGaofeng Li Youjie HuaLihui Huang Shilong ZhaoHuanping Wang Chenxia Li 《Materials Letters》2011,65(8):1176-1178
Y6Si3O9N4:Ce3+ phosphor was prepared by a solid-state reaction in reductive atmosphere. X-ray powder diffraction (XRD) analysis confirmed the formation of Y6Si3O9N4:Ce3+. Scanning electron microscopy (SEM) observation indicated that the microstructure of the phosphor consisted of irregular fine grains with an average size of about 5 μm. Photoluminescence (PL) measurements showed that the phosphor can be efficiently excited by near ultraviolet (UV) or blue light excitation, and exhibited bright green emission peaked at about 525 nm. Compared with Ce3+-doped Y4Si2O7N2 phosphors, Ce3+-doped Y6Si3O9N4 phosphors showed longer wavelengths of both excitation and emission. The Y6Si3O9N4:Ce3+ is a potential green-emitting phosphor for white LEDs. 相似文献
7.
Very small nanoparticles (size 3-5 nm) of Y2Sn2O7, Y2Sn2O7:Tb3+ and Sb3+ co-doped Y2Sn2O7:Tb3+ were prepared at a relatively low temperature of 700 °C. Y2Sn2O7 host is characterised by an emission around 436 nm, which is arising from the oxygen vacancies present in the lattice. Tb3+ emission improves significantly when Sb3+ ions are co-doped with Y2Sn2O7:Tb3+ nanoparticles. Incorporation of Sb3+ ions at the Y3+ site of Y2Sn2O7 lattice and associated lattice distortion around Tb3+/Y3+ ions brought about by the difference in the stable coordination number of Sb3+ and Y3+ ions are responsible for the improved Tb3+ emission from the co-doped samples. 相似文献
8.
Eu2+ and Dy3+ ion co-doped Sr3Al2O6 red-emitting long afterglow phosphor was synthesized by sol-gel-combustion methods using Sr(NO3)2, Al(NO3)3·9H2O, Eu2O3, Dy2O3, H3BO3 and C6H8O7·H2O as raw materials. The crystalline structure of the phosphors were characterized by X-ray diffraction, luminescent properties of phosphors were analyzed by fluorescence spectrophotometer. The effect of excitation wavelengths on the luminescent properties of Sr3Al2O6:Eu2+, Dy3+ phosphors was discussed. The emission peak of Sr3Al2O6:Eu2+, Dy3+ phosphor lays at 516 nm under the excitation of 360 nm, and at 612 nm under the excitation of 468 nm. The results reveal that the Sr3Al2O6:Eu2+, Dy3+ phosphor will emit a yellow-green light upon UV illumination, and a bright red light upon visible light illumination. The emission mechanism was discussed according to the effect of nephelauxetic and crystal field on the 4f65d1 → 4f7 transition of the Eu2+ ions in Sr3Al2O6. The afterglow time of (Sr0.94Eu0.03Dy0.03)3 Al2O6 phosphors lasts for over 600s after the excited source was cut off. 相似文献
9.
L. Wang 《Thin solid films》2010,518(17):4817-4820
Y2O3:Eu3+ red-emitting thin film phosphor was prepared by a two-step process: the cathodical deposition of thin film of yttrium hydroxide and europium hydroxide followed by an annealing process to achieve Eu3+ doped Y2O3 film. It is found that the atomic content of Eu3+ can be well controlled by simply adjusting the volume ratio of Y(NO3)3 to Eu(NO3)3 solutions. Dependence of the photoluminescence intensity on the atomic content of Eu3+ in Y2O3 was also studied. The best photoluminescence performance of Y2O3:Eu3+ thin film phosphor was achieved as atomic content of Eu3+ equal to 1.85 at.%. 相似文献
10.
In this work, two Tb3+ activated green phosphors: Y2O3:Tb3+ and YBO3:Tb3+ were prepared by hydrothermal method. Photoluminescence properties of both phosphors were studied in details. Both phosphors exhibit similar luminescent characteristics symbolized by the dominant green emission at 545 nm. Concentration quenching occurs at the Tb3+ concentration of 1.60 atomic% and 2.57 atomic% for Y2O3:Tb3+ and YBO3:Tb3+, respectively. Luminescence decay properties were characterized to better understand the mechanism of concentration quenching. Based on the calculation, the concentration quenching in both phosphors was caused by the dipole–dipole interaction between Tb3+ ions. 相似文献
11.
Aluminium oxide (Al2O3) films doped with CeCl3, TbCl3 and MnCl2 were deposited at 300 °C with the ultrasonic spray pyrolysis technique. The films were analysed using the X-ray diffraction technique and they exhibited a very broad band without any indication of crystallinity, typical of amorphous materials. Sensitization of Tb3+ and Mn2+ ions by Ce3+ ions gives rise to blue, green and red simultaneous emission when the film activated by such ions is excited with UV radiation. The overall efficiency of such energy transfer results to be about 85% upon excitation at 312 nm. Energy transfer from Ce3+ to Tb3+ ions through an electric dipole-quadrupole interaction mechanism appears to be more probable than the electric dipole-dipole one. A strong white light emission for the Al2O3:Ce3+(1.3 at.%):Tb3+(0.2 at.%):Mn2+(0.3 at.%) film under UV excitation is observed. The high efficiency of energy transfer from Ce3+ to Tb3+ and Mn2+ ions, resulting in cold white light emission (x = 0.30 and y = 0.32 chromaticity coordinates) makes the Ce3+, Tb3+ and Mn2+ triply doped Al2O3 film an interesting material for the design of efficient UV pumped phosphors for white light generation. 相似文献
12.
Y3 − xCexAl5O12 (YAG:Ce3+) phosphor powders were successfully prepared by hydrothermal-homogenous precipitation (HHP) method, under mild conditions with inexpensive aluminum and yttrium nitrates as the starting materials and urea as homogenous precipitant. The pure YAG crystalline phase could be formed after hydrothermal treatment at 100 °C for 4 h and 240 °C for 20 h and postannealing process at 1200 °C for 2 h. All of the as-prepared YAG:Ce3+ powders did not have the CeO2 phase. The photoluminescence spectrum of crystalline YAG:Ce3+ phosphors showed the emission intensity of phosphor increased with increasing the annealed temperature and reached its maximum as the molar fraction of cerium ion was 0.10, and also showed the maximum emission wavelength nearly unchanged with the calcination temperature and cerium doping concentration. 相似文献
13.
Xinghua Zhang Zunming Lu Fanbin MengFang Lu Long HuXuewen Xu Chengchun Tang 《Materials Letters》2012,66(1):16-18
A series of yellow-emitting phosphors based on a silicate host matrix, Ca3 − xSi2O7: xEu2+, was prepared by solid-state reaction method. The structure and photoluminescent properties of the phosphors were investigated. The XRD results show that the Eu2+ substitution of Ca2+ does not change the structure of Ca3Si2O7 host and there is no impurity phase for x < 0.12. The SEM images display that phosphors aggregate obviously and the shape of the phosphor particle is irregular. The EDX results reveal that the phosphors consist of Ca, Si, O, Eu and the concentration of these elements is close to the stoichiometric composition. The Ca3 − xSi2O7: xEu2+ phosphors can be excited at a wavelength of 300-490 nm, which is suitable for the emission band of near ultraviolet or blue light-emitting-diode (LED) chips. The phosphors exhibit a broad emission region from 520 to 650 nm and the emission peak centered at 568 nm. In addition, the shape and the position of the emission peak are not influenced by the Eu2+ concentration and excitation wavelength. The phosphor for x = 0.045 has the strongest excitation and emission intensity, and the Ca3 − xSi2O7: xEu2+ phosphors can be used as candidates for the white LEDs. 相似文献
14.
Yongchao JiaHui Qiao Ning GuoYuhua Zheng Mei YangYeju Huang Hongpeng You 《Optical Materials》2011,33(11):1803-1807
The blue-emitting phosphors Ca(4−x)EuxSi2O7F2 (0 < x ? 0.05) have been prepared by solid-state reaction and the photoluminescence properties have been studied systematically. The electronic structure of calcium fluoride silicate Ca4Si2O7F2 was calculated using the CASTEP code. The calculation results of electronic structure show that Ca4Si2O7F2 has an indirect band gap with 5 eV. The top of the valence band is dominated by O 2p and Si 3p states, while the bottom of the conduction band is mainly composed of Ca 3d states. Under the 350 nm excitation, the obtained sample shows a broad emission band in the wavelength range of 400-500 nm with peaks of 413 nm and 460 nm from two different luminescence centers, respectively. The relative intensity of the two peaks changes with the alteration of the Eu2+ concentration. The strong excitation bands of the powder in the wavelength range of 200-420 nm are favorable properties for the application as lighting-emitting-diode conversion phosphor. 相似文献
15.
Y2O3:Eu red-emitting nanophosphors were synthesized directly by dissolving Y2O3 and Eu2O3 in HNO3 and by using an atmospheric microwave-plasma torch for a direct continuous preparation and for mass production of Y2O3:Eu powders. Atmospheric microwave plasmas produce a high-temperature plasma flame due to ohmic heating by high frequency electric fields, revealing a maximum central temperature of 6500 ± 350 K. Therefore, the synthesized Y2O3:Eu nanophosphors from instantaneous evaporation of dissolved Y2O3 and Eu2O3 in HNO3 have favorable characteristics such as regular size and cubic equilibrium structure. The nanophosphors were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL). 相似文献
16.
K. Pimraksa P. ChindaprasirtA. Rungchet K. Sagoe-CrentsilT. Sato 《Materials Science and Engineering: A》2011,528(21):6616-6623
The syntheses of lightweight geopolymeric materials from highly porous siliceous materials viz. diatomaceous earth (DE) and rice husk ash (RHA) with high starting SiO2/Al2O3 ratios of 13.0-33.5 and Na2O/Al2O3 ratios of 0.66-3.0 were studied. The effects of fineness and calcination temperature of DE, concentrations of NaOH and KOH, DE to RHA ratio; curing temperature and time on the mechanical properties and microstructures of the geopolymer pastes were investigated. The results indicated that the optimum calcination temperature of DE was 800 °C. Increasing fineness of DE and starting Na2O/Al2O3 ratio resulted in an increase in compressive strength of geopolymer paste. Geopolymer pastes activated with NaOH gave higher compressive strengths than those with KOH. The optimum curing temperature and time were 75 °C and 5 days. The lightweight geopolymer material with mean bulk density of 0.88 g/cm3 and compressive strength of 15 kg/cm2 was obtained. Incorporation of 40% RHA to increase starting SiO2/Al2O3 and Na2O/Al2O3 ratios to 22.5 and 1.7 and enhanced the compressive strength of geopolymer paste to 24 kg/cm2 with only a marginal increase of bulk density to 1.01 g/cm3. However, the geopolymer materials with high Na2O/Al2O3 (>1.5) were not stable in water submersion. 相似文献
17.
R. MarderR. Chaim G. ChevallierC. Estournes 《Materials Science and Engineering: A》2011,528(24):7200-7206
Multiphase (MP) monoclinic and cubic Y2O3 nanoparticles, 40 nm in diameter, were densified by spark plasma sintering for 5-15 min and100 MPa at 1000 °C, 1100 °C, and 1500 °C. Densification started with pressure increase at room temperature. Densification stagnated during heating compared to the high shrinkage rate in cubic single-phase reference nanopowder. The limited densification of the MP nanopowder originated from the vermicular structure (skeleton) formed during the heating. Interface controlled monoclinic to cubic polymorphic transformation above 980 °C led to the formation of large spherical cubic grains within the vermicular matrix. This resulted in the loss of the nanocrystalline character and low final density. 相似文献
18.
Jong Seong BaeByung Kee Moon Byung Chun ChoiJung Hyun Jeong Soung Soo YiIll Won Kim Jeong Sik Lee 《Thin solid films》2003,424(2):291-295
ZnGa2O4 thin film phosphors have been deposited using a pulsed laser deposition technique on Si (1 0 0) and Al2O3 (0 0 0 1) substrates at a substrate temperature of 550 °C with various oxygen pressures 100, 200 and 300 mTorr, and various substrate temperatures of 450, 550 and 650 °C with a fixed oxygen pressure of 100 mTorr. The films grown under different deposition conditions have been characterized using microstructural and luminescent measurements. Under the different substrate temperatures, ZnGa2O4 thin films show the different crystallinity and luminescent intensity. The crystallinity and photoluminescence (PL) of the ZnGa2O4 films are highly dependent on the deposition conditions, in particular, oxygen pressure, substrate temperature, a kind of substrates. The luminescent spectra show a broad band extending from 350 to 600 nm peaking at 460 nm. The PL brightness data obtained from the ZnGa2O4 films grown under optimized conditions have indicated that the sapphire is one of the most promised substrates for the growth of high quality ZnGa2O4 thin film phosphor. 相似文献
19.
Spherical monodispersed, submicron-sized Y2O3 powder was prepared via a homogeneous precipitation method using nitrate and urea as raw materials. The structure, phase evolution and morphology of Y2O3 precursor and the calcined powder were studied by FTIR, TG/DTA, XRD and SEM methods. The sphere size of the precursor was about 250 nm and that of Y2O3 powder calcined at 800 °C for 2 h was about 200-210 nm. With the spherical Y2O3 powder and a commercial Al2O3 ultrafine powder, high transparent YAG ceramics was fabricated by vacuum sintering at 1780 °C for 6 h through a solid-state reaction method. The in-line transmittances of the as-fabricated YAG ceramics at the wavelength of 1064 nm and 400 nm were 82.8% and 79.5%, respectively, which were much higher than that of the YAG ceramics with a commercial Y2O3 powder and a commercial Al2O3 ultrafine powder directly. The superior properties are attributed to the good morphology, dispersibility and uniform grain size of the as-prepared spherical Y2O3 powder, which matches that of the commercial Al2O3 powder. 相似文献
20.
In this work, Y2O3 was evaluated as a gate insulator for thin film transistors fabricated using an amorphous InGaZnO4 (a-IGZO) active layer. The properties of Y2O3 were examined as a function of various processing parameters including plasma power, chamber gas conditions, and working pressure. The leakage current density for the Y2O3 film prepared under the optimum conditions was observed to be ~ 3.5 × 10− 9 A/cm2 at an electric field of 1 MV/cm. The RMS roughness of the Y2O3 film was improved from 1.6 nm to 0.8 nm by employing an ALD (Atomic Layer Deposition) HfO2 underlayer. Using the optimized Y2O3 deposition conditions, thin film transistors (TFTs) were fabricated on a glass substrate. The important TFT device parameters of the on/off current ratio, sub-threshold swing, threshold voltage, and electric field mobility were measured to be 7.0 × 107, 0.18 V/dec, 1.1 V, and 3.3 cm2/Vs, respectively. The stacked insulator consisting of Y2O3/HfO2 was highly effective in enhancing the device properties. 相似文献