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1.
Sm3+-activated La2O2S phosphors with good crystallinity were prepared by solid-state reaction. The formation mechanism of La2O2S formation was assumed and the phase change with different temperatures was discussed. The luminescence properties of phosphors with different sintering temperatures and different doping concentrations of Sm3+were investigated. The emission peak at 605 nm showed a well intensity can be attributed to the 4G5/2 → 6H7/2 transition of Sm3+. The optical absorption of La2O2S phosphors showed a stronger intensity in UV-vis region comparing with the Y2O2S phosphors. The long afterglow properties were investigated after the phosphors were excited with a fluorescent lamp. Phosphorescence lasted for about 3 min in the limit of light perception of the dark-adapted human eye (0.32 mcdm−2).  相似文献   

2.
The sensitive composite material was prepared by loading Pt and La2O3 into ultrafine In2O3 matric material (8 nm) synthesized by microemulsion method. A highly selective ethanol gas sensor was developed based on hot-wire type gas sensor, which was sintered in a bead (0.8 mm in diameter) to cover a platinum wire coil (0.4 mm in diameter). The gas sensor was operated by a bridge electric circuit. The influences of La2O3 and Pt additives on C2H5OH sensing properties of In2O3-based gas sensor were discussed. The addition of La2O3 resulted in a prominent selectivity for C2H5OH, and the addition of Pt improved the response rate to C2H5OH without affecting the sensitivity. The temperature and humidity characteristics of the sensor output were also investigated. The selective sensor had low power consumption, significantly minor humidity and temperature dependence, high selectivity and prominent long-term stability.  相似文献   

3.
CdIn2O4 sensor with high sensitivity and excellent selectivity for H2S gas was synthesized by using sol-gel technique. Structural, electrical and gas sensing properties of doped and undoped CdIn2O4 thick films were studied. XRD revealed the single-phase polycrystalline nature of the synthesized CdIn2O4 nanomaterials. Since the resistance change of a sensing material is the measure of its response, selectivity and sensitivity was found to be enhanced by doping different concentrations of cobalt in CdIn2O4 thick films. The sensor exhibits high response and selectivity toward H2S for 10 wt.% Co doped CdIn2O4 thick films. The current-voltage characteristics of 10 wt.% Co doped CdIn2O4 calcined at 650 °C shows one order increase in current with change in the bias voltage at an operating temperature of 200 °C for 1000 ppm H2S gas.  相似文献   

4.
CuInS2 thin films were deposited by chemical spray of aqueous solutions containing CuCl2, InCl3 and thiourea at substrate temperature of 250 °C in air and subjected to annealing at 530 °C in H2S atmosphere. Structure and composition before and after annealing were studied by XRD, EDS, XPS and Raman spectroscopy. As-sprayed films were low-crystalline, showed uniform distribution of elements in film thickness and no oxygen content. For the CuInS2 films deposited from the solutions with [Cu2+] / [In3+] = 1.0 and 1.1, H2S treatment for 30 min increased the chalcopyrite content up to 73% and 51%, respectively. CuXS phase in sprayed CIS films promotes the crystallite growth but retards the formation of chalcopyrite phase during H2S treatment.  相似文献   

5.
Two routes have been proposed for the synthesis of In2O3 powders from InCl3•4H2O and thiourea. One route involved a two-step procedure (that is, firstly, In2S3 clusters constructed with mainly nanoflakes were synthesized by heating the mixture of InCl3•4H2O and thiourea in air from room temperature to 200 °C, coupled with a subsequent washing treatment; secondly, In2O3 was obtained by calcining the In2S3 clusters in air at 600 °C for 6 h), and the other route was a one-step procedure (that is, In2O3 was synthesized directly by calcining the mixture of InCl3•4H2O and thiourea in air at 600 °C for 6 h). The resultant products were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electronic microscope and room temperature photoluminescence (RT-PL) spectra. It was observed that the In2O3 nanocrystals obtained via the two-step procedure exhibited PL peaks at about 453 and 471 nm, corresponding to the defeat-related emission; while the In2O3 submicron polyhedral crystals obtained via the one-step procedure and In2O3 pyramids obtained by calcining the only InCl3•4H2O in air at 600 °C for 6 h displayed a PL band centered at around 338 nm, corresponding to the band edge emission.  相似文献   

6.
The varistor properties of the ZnO-Pr6O11-CoO-Cr2O3-Y2O3-In2O3 ceramics were investigated for different concentrations of In2O3. The increase of In2O3 concentration slightly increased the sintered density (5.60-5.63 g/cm3) and slightly decreased the average grain size (3.4-2.9 μm). The breakdown field increased from 6023 to 14822 V/cm with increasing concentration of In2O3. The nonlinear coefficient increased from 17.6 to 44.6 for up to 0.005 mol%, whereas the further doping caused it to decrease to 36.8. In2O3 acted as an acceptor due to the donor concentration, which decreases in the range of 1.02 × 1017 to 0.24 × 1017/cm3 with increasing concentration of In2O3.  相似文献   

7.
A.B. Bodade 《Vacuum》2008,82(6):588-593
This paper reports the preparation and gas-sensing characteristic of ZnO:TiO2-based hydrogen sulfide (H2S) gas sensor with different mol% of CdO by polymerized complex method. The structural and gas-sensing properties of ZnO:TiO2 materials have been characterized using X-ray diffraction and gas-sensing measurement. The electrical resistance response of the sensor based on the materials was investigated at different operating temperatures and different gas concentrations. The sensor with 10 mol% CdO-doped ZnO:TiO2 shows excellent electrical resistance response toward H2S gas. The cross sensitivity was also checked for reducing gases like CH4, CO and H2 gas. The selectivity and sensitivity of ZnO:TiO2-based H2S gas sensor were improved by the addition of 10 mol% of CdO at an operating temperature of 250 °C.  相似文献   

8.
In this paper, a modified sol-gel method was employed to prepare nanostructured MgAl2O4 spinel powders doped with Tb3+ ions and thermally treated at 700 and 1000 °C for 3 h. The structural properties of the prepared at 700 and 1000 °C powders where characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). According to obtained XRD patterns the formation of single-phase spinels after calcination was confirmed. The XRD analyses demonstrated that the powders were single-phase spinel nanopowders with high crystallite dispersion. The Rietveld method was applied to calculate lattice parameters. The averaged spinel particle size was determined to be ∼10 nm for calcination at 700 °C and ∼20 nm at 1000 °C. The emission and excitation spectra measured at room and low temperature (77 K) for the samples calcined at 700 and 1000 °C demonstrated characteristic spectra of Tb3+ ions. The effect of MgAl2O4:Tb3+ grain sizes on luminescence properties was noticed.  相似文献   

9.
Eu3+ doped (Gd,Lu)2O3 nanopowders with particle sizes ranging from 20 to 70 nm were synthesized by the co-precipitant method using mixed precipitants, namely the mixture of ammonium hydroxide (NH3⋅H2O) and ammonium hydrogen carbonate (NH4HCO3). The precipitate precursor prepared by this method was believed to possess a basic carbonate composition and its thermal decomposition of the (Gd,Lu)2O3:Eu3+ powders were investigated by Thermogravimetric analysis and differential thermal analysis (TG-DTA). This preparation was followed by a calcination process at 800-1100 °C and corresponding phosphor structure were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Photoluminescence measurement of the (Gd,Lu)2O3:Eu3+ particles show typical red emission at the 612 nm corresponding to the 5D0 → 7F2 transition. We found that the optimal Eu3+ molar doping concentration, calcined temperature and reaction time were 7 mol%, 1000 °C, and 2 h, respectively, which is helpful to obtain the final transparent ceramics with excellent properties.  相似文献   

10.
Eu3+ (2.5 at.%) and Tb3+ (0.005-0.01 at.%) co-doped gadolinium and yttrium oxide (Gd2O3 and Y2O3) powders and films have been prepared using the sol-gel process. High density and optical quality thin films were prepared with the dip-coating technique. Gadolinium (III) 2,4-pentadionate and yttrium (III) 2,4-pentadionate were used as precursors, and europium and terbium in their nitrate forms were used as doping agents. Chemical and structural analyses (infrared spectroscopy, X-ray diffraction and high-resolution transmission electron microscopy) were conducted on both sol-gel precursor powders and dip-coated films. The morphology of thin films heat-treated at 700 °C was studied by means of atomic force microscopy. It was shown that the highly dense and very smooth films had a root mean roughness (RMS) of 2 nm ± 0.2 (A = 0.0075 Tb3+) and 24 nm ± 3.0 (B = 0.01 Tb3+). After treatment at 700 °C, the crystallized films were in the cubic phase and presented a polycrystalline structure made up of randomly oriented crystallites with grain sizes varying from 20 to 60 nm. The X-ray induced emission spectra of Eu3+- and Tb3+-doped Gd2O3 and Y2O3 powders showed that Tb3+ contents of 0.005, 0.0075 and 0.01 at.% affected their optical properties. Lower Tb3+ concentrations (down to 0.005 at.%) in both systems enhanced the light yield.  相似文献   

11.
Influence of incorporation of Ga in amorphous In-Zn-O transparent conductive oxide films was investigated as a function of Zn/(Zn + In). For In-Zn-O films with no Ga2O3, the range of Zn/(Zn + In) ratio where the amorphous phase appears became narrow at a substrate temperature of 250 °C. With increasing Ga2O3 quantity, amorphous films were obtained even at a high substrate temperature of 250 °C in a wider range of Zn/(Zn + In) than that of In-Zn-O films with no Ga2O3. This means that the trend of crystallization at higher substrate temperature was disturbed with additional Ga incorporation. For the film deposited from ZnO:Ga (Ga2O3: 4.5-7.5 wt%) and In2O3 targets, we obtained a resistivity of 2.8 × 10−4 Ω cm, nearly the same value as that for an In-Zn-O film with no Ga2O3. The addition of more than 7.5 wt% Ga2O3 induced a widening of the optical band gap.  相似文献   

12.
The structural properties of La2O3 and Al2O3-La2O3 binary oxides prepared by sol-gel were studied by XRD, HRTEM and UV-vis. The binary oxides with high lanthana contents show an amorphous structure after calcination at 650 °C. At calcination temperatures higher than 1000 °C there is a phase transformation from the amorphous state to the crystalline LaAlO3 with a perovskite structure. The structure of La2O3 is consistent with the hexagonal system; however, some crystalline microdomains with a monoclinic structure were detected by HRTEM. Islands of La2O3 and LaAl11O18 phases were detected at high lanthana concentration in the binary oxide. The modification in the coordination shell of the Al3+ cations due to the interaction with La3+ cations confirms the formation of phases with a perovskite structure and the presence of islands of the LaAl11O18 phase.  相似文献   

13.
We present luminescence, luminescence excitation and luminescence time resolved spectra of La2Be2O5:Pr3+ system. We used high pressure spectroscopy approaches, with high pressure applied in diamond anvil cell (DAC) and sapphire anvil cell (SAC), for detailed analysis of luminescence related to the 4f5d → 4f2 and 4f2 → 4f2 transitions. We present effect of up-converted luminescence related to 4f5d → 4f2 transition excited with 488 nm. We also discussed possibility of existence of praseodymium trapped exciton (PTE) states in La2Be2O5:Pr3+ system. Lack of the PTE is attributed to high quantity of bulk modulus of this material.  相似文献   

14.
Li2TiO3 ceramics were prepared at the sintering temperatures from 1050 to 1250 °C. The optimal microwave dielectric properties were ?r = 23.29, Q × f = 15,525 GHz (5.9 GHz), and τf = 35.05 ppm/ °C for the sample sintered at 1200 °C. The microwave dielectric properties were improved obviously when the Li2TiO3 ceramics were sintered at low temperatures with small additions of H3BO3 (B2O3 in the form of H3BO3). Only monoclinic Li2TiO3 was found in the pure or H3BO3-doped Li2TiO3 ceramics. About 1.0 wt.% H3BO3 addition aided the sintering of Li2TiO3 ceramics effectively while excessive H3BO3 (≥2.5 wt.%) was not favorable. Typically the best microwave dielectric properties were ?r = 23.28, Q × f = 37,110 GHz (6.3 GHz), and τf = 30.43 ppm/ °C for the 1.0 wt.% H3BO3-doped Li2TiO3 ceramic sintered at 920 for 3 h, which is promising for LTCC applications.  相似文献   

15.
Transparent La2Hf2O7 (LHO) ceramics were, for the first time, successfully fabricated from combustion-synthesized powders. Nanosized La2Hf2O7 powders were obtained through combustion reaction, using glycine or EDTA as a fuel. The as-made powders were isostatically pressed at 180 MPa and then sintered at 1850 °C for 6 h in hydrogen atmosphere. The resulting ceramics have high optical transmittance.  相似文献   

16.
Lanthanide-doped uniform pure cubic phase Y2O3 hollow microspheres have been successfully synthesized via a facile, high yield urea-based coprecipitation route with assistant of carbon spheres templates. The diameter and shell thickness of the microspheres can be manipulated by adjusting carbon sphere templates. Under a 980 nm excitation, Yb3+/Er3+, Er3+, Yb3+/Tm3+-doped Y2O3 hollow microspheres emit bright upconversion red, green, blue light with high purity, respectively, while Eu3+, Eu3+/Tb3+-doped Y2O3 hollow microspheres exhibit intense downconversion red light under the excitation of 254 nm ultraviolet light. Especially, the 610 nm emission intensity of Eu3+ in the Eu3+/Tb3+-codoped Y2O3 hollow microspheres is almost 5 times of that in the Y2O3:Eu3+ hollow microspheres indicating the occurring of the energy transfer from Tb3+ to Eu3+ ions.  相似文献   

17.
The vacuum ultraviolet excited luminescent properties of Eu3+, Tb3+, Dy3+, Sm3+ and Tm3+ in the matrices of Ca4Y6(SiO4)6O were investigated. The bands at about 173 nm in the vacuum ultraviolet excited spectra were attributed to host lattice absorption of the matrix Ca4Y6(SiO4)6O. For Eu3+-doped samples, the O2− → Eu3+ CTB was identified at 258 nm. Typical 4f-5d absorption bands in the region of 195-300 nm were observed in Tb3+-doped samples. For Dy3+-doped and Sm3+-doped samples, the broad excitation bands consisted of host absorptions, CTB and f-d transition. For Tm3+-doped samples, the O2− → Tm3+ CTB was located at 191 nm. About the color purity and emission intensity, Ca4Y6(SiO4)6O:Tb3+ is an attractive candidate of green light PDP phosphor, and Ca4Y6(SiO4)6O:Dy3+ has potential application in the field of mercury-free lamps.  相似文献   

18.
The luminescence lifetime of the 0.01 mol.%-0.1 mol.% Er3+- and 0–20 mol.% Y3+-codoped Al2O3 powders prepared at a sintering temperature of 900°C in a non-aqueous sol-gel method has been investigated to explore the enhanced mechanism of photoluminescence properties of the Er3+-doped Al2O3 by Y3+ codoping. For the 0.1 mol.% Er3+-Y3+-codoped Al2O3 powders, the measured lifetime of Er3+ gradually increases with increasing Y3+ concentration. Consequently, codoping with 20 mol.% Y3+ leads to an increase in the measured lifetime from 3.5 to 5.8 ms. By comparing the measured lifetime for different Er3+ concentrations in the Al2O3 powders, the radiative lifetime of both the Er3+-doped and the Er3+-Y3+-codoped Al2O3 powders is estimated to be about 7.5 ms. Infrared absorption spectra indicate that Y3+ codoping does not change the-OH content in the Er3+-Y3+-codoped Al2O3 powders. The prolonged luminescence lifetime of the 4I13/2 level of Er3+ in Er3+-doped Al2O3 powders by Y3+ codoping is ascribed to the decrease in the energy transfer rate between the Er3+ ions and the Er3+ and -OH, respectively, due to the suppressed interaction between Er3+ ions.  相似文献   

19.
Fast response detection of H2S by CuO-doped SnO2 films prepared was prepared by a simple two-step process: electrodeposition from aqueous solutions of SnCl2 and CuCl2, and oxidization at 600 °C. The phase constitution and morphology of the CuO-doped SnO2 films were characterized by X-ray diffraction and scanning electron microscopy. In all cases, a polycrystalline porous film of SnO2 was the product, with the CuO deposited on the individual SnO2 particles. Two types of CuO-doped SnO2 films with different microstructures were obtained via control of oxidation time: nanosized CuO dotted island doped SnO2 and ultra-uniform, porous, and thin CuO film coated SnO2. The sensor response of the CuO doped SnO2 films to H2S gas at 50–300 ppm was investigated within the temperature range of 25–125 °C. Both of the CuO-doped SnO2 films show fast response and recovery properties. The response time of the ultra-uniform, porous, and thin CuO coated SnO2 to H2S gas at 50 ppm was 34 s at 100 °C, and its corresponding recovery time was about 1/3 of the response time.  相似文献   

20.
This paper deals with the influence of dysprosium oxide doping on thermophysical properties of LaMgAl11O19 ceramics. LaMgAl11O19 ceramic powders doped with different contents of dysprosium oxide were pressureless-sintered at 1700 °C for 10 h in air to fabricate dense bulk ceramics. La1−xDyxMgAl11O19 (= 0, 0.1, 0.2, 0.3) ceramics have a relative density of 90.7–96.0%, and exhibit a single phase of magnetoplumbite structure. Thermal diffusivity and thermal expansion coefficients of La1−xDyxMgAl11O19 ceramics were measured with a laser flash method and a high-temperature dilatometer. Thermal diffusivity of La1−xDyxMgAl11O19 ceramics decreases with increasing Dy2O3 content at identical temperature levels. The measured thermal conductivity of La1−xDyxMgAl11O19 ceramics is located in the range of 2.52–2.89 W m−1 K−1 at 1200 °C. Thermal expansion coefficient of La0.8Dy0.2MgAl11O19 ceramic is slightly higher than that of undoped LaMgAl11O19 ceramic at identical temperature levels.  相似文献   

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