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1.
Gd2O3 thin films as high-κ gate dielectrics were deposited directly on Si(001) substrates by magnetron sputtering at a pressure of 1.3 Pa and different temperatures. X-ray diffraction results revealed that all the films grown from 450 to 570 ℃ were crystalline, and the Gd2O3 thin films consisted of a mixture of cubic and monoclinic phases. The growth temperature was a critical parameter for the phase constituents and their relative amount. Low temperature was favorable for the formation of cubic phase while higher temperature gave rise to more monoclinic phase. All the Gd2O3 thin films grown from different temperatures exhibited acceptable electrical properties, such as low leakage current density (JL) of 10-5 A/cm^2 at zero bias with capacitance equivalent SiO2 thickness in the range of 6-13 nm. Through the comparison between films grown at 450 and 570 ℃, the existence of monoclinic phase caused an increase in JL by nearly one order of magnitude and a reduction of effective dielectric constant from 17 to 9.  相似文献   

2.
The Gd2O2CO3:Eu^3+ with type-Ⅱ structure phosphor was successfully synthesized via flux method at 400 ℃ and their photoluminescence properties in vacuum ultraviolet (VUV) region were examined. The broad and strong excitation bands in the range of 153-205 nm owing to the CO3^2- host absorption and charge transfer (CT) of Gd^3+-O2^- were observed for Gd2O2CO3:Eu^3+. Under 172 nm excitation, Gd2O2CO3:Eu^3+ exhibited strong red emission with good color purity, indicating Eu^3+ ions located at low symmetry sites and the chromaticity coordination of luminescence for Gd2O2CO3:Eu^3+ was (x=0.652, y=0.345). The photoluminescence quenching concentration of Eu^3+ excited by 172 nm for Gd2O2CO3:Eu^3+ was about 5%. Gd2O2CO3:Eu^3+ would be a potential VUV-excited red phosphor applied in mercury-free fluorescent lamps.  相似文献   

3.
CdGd2 (WO4)4 -δ single crystal was grown using the Czochralski's method. The crystal structure was tetragonal seheelite with lattice parameters a = b = 0.5203 nm and c = 1. 1359 nm. There were vacancies of (WO4)^2- , therefore, there were some Gd^2+ ions. Langevin paramagnetism and anisotropy were observed from the δ-T curves at room temperature. The susceptibility X//was 3.5018×10^-3, and X⊥ was 3.4403× 10^-2. The anisotropy was also observed in the electron spin resonance (ESR) experiments. The anisotropic Land6 factors were g//= 2. 1333 and g~ = 2. 8411. The direction of easy magnetization was in the α-b plane. Anisotropic paramagnetic Curie constants C//and C⊥ were not only related to macroscopic a that was observed through the experiment, but were also related to J⊥ and J//, which were the microscopic quantum numbers of the Gd^2+ and Gd^3| ions. Based on the detailed analyses, the proportion of 36.8% of Gd^3+ ions to 63.2% of Gd^2+ ions in the Gd ions of the CdGd2(WO4)4-δ crystal was calculated, and δ was 0.638 in the single crystal.  相似文献   

4.
(Bi2O3)0.73(Y2O3)0.27 fine powders prepared by wet chemical precipitation method were cold isostatically pressed to form solid electrolyte tubes, and sintered at 900 ℃ for 10 h in the air. Their pumping oxygen characteristics in non-dehydrated Ar gas were investigated, where a ZrO2 (Y2O3 stabilized) oxygen sensor was used to measure the oxygen partial pressure Po2. The results showed that the Po2 value reached magnitudes of 1×10^-2-1×10^-10 Pa at the applied pumping oxygen voltage of 0.5 V, 1×10^-37-1×10^-27 Pa at 1.0 V and 1×10^-53-1×10^47 Pa at 2.0 V within the temperature range from 550 to 650 ℃. Moreover, no cracks were found in the tested solid electrolyte tubes. Thus, the Bi2O3-Y2O3 system might be used in solid electrolyte oxygen pump for purifying gases.  相似文献   

5.
For the 90% v/v CH3OH–10% v/v 7 M HNO3 system the affinity series of nitrate complexes of rare earth elements(III) for the strongly basic anion-exchanger Wofatit SBW×4% DVB was determined. The effect of ammonium nitrate and polar organic solvent addition on the effectiveness of separation of the ion-exchanging pair Y(III)–Nd(III) on Wofatit SBW×4% DVB as well as that of macrocomponent (yttrium) concentration on the yield of the purification process on Wofatit SBW×6% DVB were investigated. The weight and bed distribution coefficients for individual rare earth elements(III) were determined. It was shown that the neodymium content in the purified yttrium(III) can be decreased from 1% to 10−3% under controlled conditions.  相似文献   

6.
Nd^3+: Gd3Ga5O12(Nd : GGG) nanopowder for transparent laser ceramics was synthesized using sol-gel method. XRD, SEM, and fluorescence spectrum were used to study the properties of Nd^3+ :Gd3Ga5O12 nanopowder. XRD patterns of samples show that it has a cubic structure. Meanwhile, pure Nd:GGG crystals were obtained at 1000 ℃ for 12 h. SEM photographs show that dispersed, uniform, ball-like Nd:GGG nanopowder is obtained. Both XRD and SEM results show that the crystallization degree and the grain size increase with the increase in calcining temperature. Analysis of fluorescence spectrum shows that fluorescence emission occurs at 1062.7 nm, which is the result of Nd^3+ (^4F3/2→^4I11/2) transition. Homogenous Nd : GGG nanopewder with a small grain size synthesized using the sol-gel method is favorable for sintering the transparent ceramic, which proves that the nanopewder obtained is suitable as a precursor for preparing GGG transparent ceramics.  相似文献   

7.
K.  Lemanski  Deren    A.  Gagor    W.  Strek 《中国稀土学报(英文版)》2009,27(4):560-563
Absorption, excitation and emission spectra as well as decay time measurements at 10, 77, and 300 K were performed for Ga3Gd3Sc2O12 garnet single-crystal doped with Cr3+ and Nd3+ ions. Strong reabsorption of Cr3+ emission by Nd3+ absorption lines was observed. The assignments of f–f and d–d transitions were proposed. The broad emission band of chromium ions is an indication that weak/intermediate crystal field strength is present at the Cr3+ site.  相似文献   

8.
重型发电燃气轮机低排放、高效率的发展目标,要求燃气轮机透平的进气温度不断提高。热障涂层作为保护金属热端部件的重要手段,是实现这一目标的关键技术之一。目前世界上最先进的J级燃气轮机的透平进口温度已经达到1600℃,热端部件表面温度超过1250℃,传统的YSZ热障涂层已经不能满足这一发展需求,因此迫切需要开发温度更高、热导率更低的新型热障涂层。本文对La_2(Zr_(0.7)Ce_(0.3))_2O_7(以下简称LZ7C3)热障涂层在重型发电燃气轮机中的应用进行了初步验证。结果表明,LZ7C3涂层具有比常规YSZ热障涂层更低的热导率(0.79~0.48Wm~(-1)K~(-1),相对传统YSZ涂层下降30%以上),且在1250℃的高温火焰台架试验中表现出优良的热循环寿命( 7370次),具有良好的应用前景。  相似文献   

9.
Polycrystalline Gd2(MoO4)3:Dy3+ phosphors have been synthesized by high temperature solid-state reaction method. The phosphors were characterized with X-ray diffractometer, thermogravimetric analysis and different scanning calorimeter, scanning electron microscopy, and photoluminescence spectrofluorimeter. Several peaks at 351, 389, 425, 452, and 472 nm appeared in photoluminescence excitation spectrum, which matched well with the emission of the ultraviolet (UV) and blue-light emitting diode (LED) chips. Upon excitation at 389 nm UV light, intense emissions centered at 484, 575 and 668 nm were attributed to the transitions of 4F9/26H15/2, 4F9/26H13/2 and 4F9/26H11/2 of Dy3+, respectively. The chromaticity coordinates and correlative color temperatures have been calculated and presented in the Commission International de I'Eclairage (CIE) diagrams. The results indicated that Gd1.9(MoO4)3:Dy0.13+ with CIE coordinates of (x=0.38, y=0.41) and the correlative color temperature of 4134 K is a potential candidate for white LEDs.  相似文献   

10.
The structure and magnetic properties of Gd2Fe15.5Cr1.5 compound were investigated by means of X-ray diffraction and magnetization measurements.The Gd2Fe15.5Cr1.5 compound had a rhombohedral Th2Zn17-type structure.The Curie temperature of Gd2Fe15.5Cr1.5 compound was about 570 K.This value was about 60 K higher than that of the mother compound Gd2Fe17.Negative thermal expansion was found in Gd2Fe15.5Cr1.5 compound in a broad temperature range 294-572 K by X-ray dilatometry.The coefficient of the average thermal expansion was =-3.87×10-6 K-1 in 294-512 K,and-1.58×10-5 in 512-572 K.The magnetostriction deformations from 294 to 532 K were calculated by means of the differences between the experimental values of the lattice parameters and corresponding values extrapolated from the paramagnetic range.The result showed that the spontaneous volume magnetostrictive deformation ωS decreased linearly from 4.73×10-3 to 0.11×10-3 with the temperature increasing from 294 to 532 K.The analysis showed that the ωS mainly came from the contribution of the spontaneous linear magnetostrictive λc along the c axis.  相似文献   

11.
The process to prepare pure phase of hexagonal Y2O2S was investigated. Effect of mixed flux of Na2CO3 and S amounts was studied. The phase composition and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the single phase of Y2O2S with smooth morphology could not be obtained as the molar ratio of Y2O3, Na2CO3 and S was in the range of 1:(0.5-1):(2-3) until the molar ratio was increased to 1:1.5:4. Different Er3+ concentration doped Y2O2S...  相似文献   

12.
The electrochemical behaviour of samarium was investigated in LiF-BeF2 system on an inert (Mo) electrode by cyclic voltammetry and chronopotentiometry at 804, 833, 847 and 872 K. Redox process Sm3++e-→Sm2+ was recognized and analysed. Cyclic voltammetry data suggested that at potential sweep rates lower than 0.25 V/s, the reduction was limited by the diffusion of Sm3+ ions. It was not possible to observe reduction process of Sm2++2e-→Sm0 due to insufficient electrochemical stability of LiF-BeF2. Diffusion coefficients of Sm3+ ions in LiF-BeF2 were calculated from voltammetric and chronopotentiometric data in the temperature range 804-872 K. Diffusion coefficient values obeyed Arrhenius law. Activation energy was calculated to be 102.5 kJ/mol.  相似文献   

13.
La2O2CO3 was prepared by calcination of La2 (CO3)3 in the air. Catalysts Ni-Fe/La2O2CO3 with different mole ratios of Ni to Fe, Ni/La2O2CO3 and Fe/La2O2CO3 were prepared by impregnation method. The catalytic properties were evaluated on steam reforming of ethanol (SRE) from 300 to 700 ℃ under atmospheric pressure and the samples were characterized by Brunauer-Emmett-Teller method (BET), X-ray diffraction (XRD) and temperature programmed reduction (TPR). The results showed that Ni-Fe bimetallic catalysts exh...  相似文献   

14.
Nanophosphor with the nominal composition of Ca0.8 Zn0.2 TiO3 : Pr3 + , Na^+ (CZTOPN) was synthesized at relatively low temperature by the sol-gel method. Metal ions were dispersed by citric acid in ethylene glycol solvent and then react with Ti(OC4H9)4 to form sol and gel. The decomposition process of the precursor, and crystallization and particle size of CZTOPN were examined by thermal analysis (TG-DSC), powder X-ray diffraction (XRD), and scan election microscopy (SEM). Results of TG-DSC and XRD reveal that the composition of Ca0.8 Zn0.2 TiO3 : Pr3 + , Na^+ changes with the sintering temperature. SEM data indicate that the diameter of particles is under 50 nm even if the sintering temperature increases to 1000 ℃. In contrast to a solid state reaction, the excitation spectra of samples synthesized by the sol-gel method shift blue about 10 nm and the emission intensity at 617 nm increases significantly.  相似文献   

15.
Nanoscale RE3+ (RE=Ce, Tb) doped and codoped lutetium pyrosilicate Lu2Si2O7 (LPS) phosphors were prepared by using the sol-gel method. Heat treatment was performed in the temperature range from 900 to 1100 °C. The crystal structure was analyzed by X-ray diffraction (XRD). The results showed that the β-type structure of LPS was obtained at 1100 °C. The excitation spectra in the UV and VUV ranges and the emission spectra of the samples were measured at room temperature, and their luminescent properties were studied. The energy transfer from Ce3+ to Tb3+ in the codoped samples were observed and discussed.  相似文献   

16.
The effect of Eu-substitution on the density and thermoelectric properties of ternary sulfide Ce3–xEuxS4 (0≤x≤0.8) compacts was investigated. Ce3–xEuxS4 powders were prepared via the sulfurization of the oxide using CS2 gas at 1473 K. The pressureless sintered Ce3–xEuxS4 compacts in the atmosphere were crystallized in the γ-phase. The density of the Ce3–xEuxS4 compacts increased with the increasing of Eu-substitution. Eu-substitution yielded a higher Seebeck coefficient and lower electrical resistivity. The highest value of the thermoelectric power factor of 1.41×10−4 W/K2m was obtained for the Ce2.2Eu0.8S4 compact at 673 K. It indicated that Eu-substitution was effective for improving thermoelectric properties of Ce3–xEuxS4.  相似文献   

17.
To take the advantage of gadolinium(Gd) in developing and manufacturing RE-permanent magnets,the magnetic properties and phase precipitation behavior of Gd2Fe14B alloys prepared by melt spinning were investigated in this work.The results show that optimally direct quenched nanocrystalline Gd2Fe14B alloy exhibits the magnetic properties with remanence Jr of 0.51 T,coercivity Hc of 187 kA/m,and maximum energy product(BH)max  相似文献   

18.
The temperature dependence of the microwave absorption of conventionally heated nonstoichiometric ferrous oxide (Fe0.925O) was characterized via the cavity perturbation technique between 294 K and 1373 K (21 °C and 1100 °C). The complex relative permittivity and permeability of the heated Fe0.925O sample slightly change with temperature from 294 K to 473 K (21 °C to 200 °C). The dramatic variations of permittivity and permeability of the sample from 473 K to 823 K (200 °C to 550 °C) are partially attributed to the formation of magnetite (Fe3O4) and metal iron (Fe) from the thermal decomposition of Fe0.925O, as confirmed by the high-temperature X-ray diffraction (HT-XRD). At higher temperatures up to 1373 K (1100 °C), it is found that Fe0.925O regenerates and remains as a stable phase with high permittivity. Since the permittivity dominates the microwave absorption of Fe0.925O above 823 K (550 °C), resulting in shallow microwave penetration depth (~0.11 and ~0.015 m at 915 and 2450 MHz, respectively), the regenerated nonstoichiometric ferrous oxide exhibits useful microwave absorption capability in the temperature range of 823 K to1373 K (550 °C to 1100 °C).  相似文献   

19.
Two novel washcoats Ce0.8Zr0.15La0.05Oδ and Ce0.8Zr0.2O2 was prepared by an impregnation method, which acted as a host for the active Pd component to prepare Pd/Ce0.8Zr0.15La0.05Oδ/substrate and Pd/Ce0.8Zr0.2O2/substrate monolithic catalysts for toluene combustion. The washcoats was characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauner-Emmett-Teller (BET), and H2-temperature-programmed reduction (H2-TPR). The result indicated that both the washcoats had strong vibration-shock resistance according to ultrasonic test. Doping La3+ into CeO2-ZrO2 solid solution could generate more oxygen vacancies, and could inhibit the sinter of CeO2-ZrO2 solid solution when calcined at high temperatures (800, 900 and 1000 °C). The washcoat Ce0.8Zr0.15La0.05Oδ had much better redox properties. The reductive temperature of Ce4+ species shifted to low temperature by 60 °C when the washcoats calcined at high temperatures (800, 900 and 1000 °C). The Pd/Ce0.8Zr0.15La0.05Oδ/substrate monolithic catalyst calcination at 500 °C had the best catalytic activity and the 95% toluene conversion at a temperature as low as 190 °C. When calcined at low temperature (500 and 700 °C), the catalytic activity has little improvement, however, when calcined at high temperature, the catalytic activity of Pd/Ce0.8Zr0.15La0.05Oδ/substrate monolithic catalysts had significant improvement. As catalyst washcoat, the Ce0.8Zr0.15La0.05Oδ had better thermal stability than the washcoat Ce0.8Zr0.2O2, the developed Pd/Ce0.8Zr0.15La0.05Oδ/substrate monolithic catalyst in this work was promising for eliminating Volatile organic compounds.  相似文献   

20.
It is well known that sulfur dioxide(SO2) , morethan50%of which arise fromcombustion of fossil fu-els ,are precursors of acidrain andtheir emission pos-es a global threat tothe atmosphere .Environmental a-gencies have ,therefore ,regulated emissions of SO…  相似文献   

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