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1.
Effects of Gd Substitution on Sintering and Optical Properties of Highly Transparent (Y0.95−xGdxEu0.05)2O3 Ceramics
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Bin Lu Ji‐Guang Li Hidehiko Tanaka Xudong Sun Yoshio Sakka 《Journal of the American Ceramic Society》2015,98(8):2480-2487
Highly transparent (Y0.95?xGdxEu0.05)2O3 (x = 0.15–0.55) ceramics have been fabricated by vacuum sintering at the relatively low temperature of 1700°C for 4 h with the in‐line transmittances of 73.6%–79.5% at the Eu3+ emission wavelength of 613 nm (~91.9%–99.3% of the theoretical transmittance of Y1.34Gd0.6Eu0.06O3 single crystal), whereas the x = 0.65 ceramic undergoes a phase transformation at 1650°C and has a transparency of 53.4% at the lower sintering temperature of 1625°C. The effects of Gd3+ substitution for Y3+ on the particle characteristics, sintering kinetics, and optical performances of the materials were systematically studied. The results show that (1) calcining the layered rare‐earth hydroxide precursors of the ternary Y–Gd–Eu system yielded rounded oxide particles with greatly reduced hard agglomeration and the particle/crystallite size slightly decreases along with increasing Gd3+ incorporation; (2) in the temperature range 1100°C–1480°C, the sintering kinetics of (Y0.95?xGdxEu0.05)2O3 is mainly controlled by grain‐boundary diffusion with similar activation energies of ~230 kJ/mol; (3) Gd3+ addition promotes grain growth and densification in the temperature range 1100°C–1400°C; (4) the bandgap energies of the (Y0.95?xGdxEu0.05)2O3 ceramics generally decrease with increasing x; however, they are much lower than those of the oxide powders; (5) both the oxide powders and the transparent ceramics exhibit the typical red emission of Eu3+ at ~613 nm (the 5D0→7F2 transition) under charge transfer (CT) excitation. Gd3+ incorporation enhances the photoluminescence and shortens the fluorescence lifetime of Eu3+. 相似文献
2.
《Journal of the European Ceramic Society》2020,40(6):2426-2431
To obtain red-emitting luminescent material for high-power UV LED and UV LD applications, an additive-free Y2O3:Eu3+ phosphor ceramic was successfully prepared in this work. The nitrate pyrogenation method is applied to obtain raw nanopowders with high reactivity, and a hybrid sintering method combining low-temperature presintering and subsequent hot isostatic pressing (HIP) is then applied to realize full densification of the final ceramic products. The effects of the presintering temperature on the density, microstructural, and optical properties are investigated in detail. The HIP-treated Y2O3:Eu3+ ceramic presintered at 1450 °C exhibits a high transmittance near 80 % at 600 nm. Due to the nonuse of sintering additives, the thermal conductivity of Y2O3:Eu3+ ceramic product reaches 10.9 Wm−1 K−1 at room temperature. The achieved Y2O3:Eu3+ ceramic also exhibits good applicability under the excitation of a UV LED chip and UV laser light, showing promise as a color converter for high-power UV LED and UV LD applications. 相似文献
3.
Fabrication and Characterization of Transparent (Y0.98−xTb0.02Eux)2O3 Ceramics with Color‐Tailorable Emission
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Bin Lu Ji‐Guang Li Xudong Sun Yoshio Sakka 《Journal of the American Ceramic Society》2015,98(12):3877-3883
Transparent (Y0.98?xTb0.02Eux)2O3 (x = 0–0.04) ceramics with color‐tailorable emission have been successfully fabricated by vacuum sintering at the relatively low temperature of 1700°C for 4 h. These ceramics have the in‐line transmittances of ~73%–76% at 613 nm, the wavelength of Eu3+ emission (the 5D0→7F2 transition). Thermodynamic calculation indicates that the Tb4+ ions in the starting oxide powder can essentially be reduced to Tb3+ under ~10?3 Pa (the pressure for vacuum sintering) when the temperature is above ~394°C. The photoluminescence excitation (PLE) spectra of the transparent (Y0.98?xTb0.02Eux)2O3 ceramics exhibit one spin‐forbidden (high‐spin, HS) band at ~323 nm and two spin‐allowed (low‐spin, LS) bands at ~303 and 281 nm. Improved emissions were observed for both Eu3+ and Tb3+ by varying the excitation wavelength from 270 to 323 nm, without notably changing the color coordinates of the whole emission. The transparent (Y0.98Tb0.02)2O3 ceramic exhibits the typical green emission of Tb3+ at 544 nm (the 5D4→7F5 transition). With increasing Eu3+ incorporation, the emission color of the (Y0.98?xTb0.02Eux)2O3 ceramics can be precisely tailored from yellowish‐green to reddish‐orange via the effective energy transfer from Tb3+ to Eu3+ under the excitation with the peak wavelength of the HS band. At the maximum Eu3+ emission intensity (x = 0.02), the ceramic shows a high energy‐transfer efficiency of ~85.3%. The fluorescence lifetimes of both the 544 nm Tb3+ and 613 nm Eu3+ emissions were found to decrease with increasing Eu3+ concentration. 相似文献
4.
Danlei Yin Jun Wang Peng Liu Haiyong Zhu Bingqing Yao Zhili Dong Dingyuan Tang 《Journal of the American Ceramic Society》2019,102(12):7462-7468
Transparent 0.6 at% Nd:Y2O3 ceramics were fabricated by vacuum sintering at 1550°C and hot isostatic pressing (HIP) at 1540°C. The ceramics sintered at such temperatures had good homogeneity with dense microstructures, without any residual pores and secondary phases. The in-line transmittance reached 81.6% at 1000 nm and remained 81.1% at 650 nm. Continuous wave (CW) laser operation of an uncoated ceramic slab was evaluated. A maximum output power of 3.6 W with slope efficiency of 45.2% at 1.08 μm was obtained. 相似文献
5.
Zhigang Sun Ziyun Chen Mengyao Wang Bin Lu 《Journal of the American Ceramic Society》2020,103(2):809-818
We first report the novel Ce3+-activated and Lu3+-stabilized gadolinium aluminate garnet (GAG) transparent ceramics derived from their precipitation precursors via a facile co-precipitation strategy using ammonium hydrogen carbonate (AHC) as the precipitant. The resulting precursors in liquid phase were substantially homogeneous solid solutions and could directly convert into sinterable garnet powders via pyrolysis. Substituting 35 at.% of Lu3+ for Gd3+ was effective to stabilize the cubic GAG garnet structure and transparent (Gd,Lu)3Al5O12:Ce ceramics were successfully fabricated by vacuum sintering at 1715°C. The ceramic transparency was improved by optimizing the particle processing conditions and the best sample had an in-line transmittance of ~70% at 580 nm (Ce3+ emission center) and over 80% in partial infrared region with a fine average grain size of ~4.5 μm. Transparent (Gd,Lu)3Al5O12:Ce ceramics have a short critical wavelength (<200 nm) and a maximal infrared cut-off at ~6.6 μm. Both the (Gd,Lu)3Al5O12:Ce phosphor powder and the transparent ceramic exhibited characteristic yellow emission of Ce3+ with strong broad emission bands from 490 to 750 nm upon UV excitation into two groups of broad bands around 340 and 470 nm. The photoluminescence and photoluminescence excitation intensities as well as the quantum yield were greatly enhanced via high-temperature densification. Both the phosphor powder and ceramic bulk had short effective fluorescence lifetimes. 相似文献
6.
Transparent ceramics have become a research hotspot in the preparation of fluorescent materials in recent years, because of their excellent physical and chemical properties and high transparency. Gadolinium aluminate, as a stable matrix material, is often doped with various active ions to obtain luminescence with different colors. However, it is very difficult to fabricate gadolinium aluminate transparent ceramics by a traditional method, although they are the charming solid lighting materials. Here, we developed a pressureless sintering method to prepare GdAlO3:Mn (GAP:Mn) transparent ceramic films, which were prepared by spin coating layered rare-earth hydroxide (LRH) on amorphous alumina substrate and sintering at 1550°C for 2 h. Through the interface reaction, the Al2O3 reacted with Gd2O3 to form mesophase Gd4Al2O9 below 1550°C. However, the final products are GdAlO3 at 1550°C. The GAP:Mn4+ film exhibits a high transmittance of about 90%. Under UV excitation at 310 nm, the ceramic film outputs deep red and NIR emissions, which are both arising from the 2Eg–4A2g transition of Mn4+. Due to the electron traps arising from unequal valence substitution, the ceramic film exhibits a negative thermal quenching phenomenon. The ceramic film has a good luminescence thermal stability, because its emission intensity at 150°C maintains over 72% that at room temperature. This work may pave a new way to fabricate transparent ceramics using LRHs. 相似文献
7.
《Ceramics International》2016,42(15):16640-16643
Transparent Y2O3 ceramics were fabricated by the solid-state reaction and vacuum sintering method using La2O3, ZrO2 and Al2O3 as sintering aids. The microstructure of the Y2O3 ceramics sintered from 1550 °C to 1800 °C for 8 h were analyzed by SEM. The sintering process of the Y2O3 transparent ceramics was optimized. The results showed that when the samples were sintered at 1800 °C for 8 h under vacuum, the average grain sizes of the ceramics were about 3.5 µm. Furthermore, the transmittance of Y2O3 ceramic sintered at 1800 °C for 8 h was 82.1% at the wavelength around the 1100 nm (1 mm thickness), which was close to its theoretical value. Moreover, the refractive index of the Y2O3 transparent ceramic in the temperature range from 30 °C to 400 °C were measured by the spectroscopic ellipsometry method. 相似文献
8.
《Ceramics International》2022,48(13):18716-18722
All-inorganic fluorescent materials with high luminescence efficiency, high thermal stability and adjustable spectrum are urgently needed, especially for high-power white LEDs. In this work, Y2.84Lu0.1Al5O12: 0.06Ce3+ fluorescent ceramics were prepared firstly by vacuum sintering technology, and then Y2.84Lu0.1Al5O12: 0.06Ce3+/SrAlSiN3: Eu2+ composite fluorescent ceramics were synthesized by technology screen-printing and laser ablation. Under 460 nm excitation, the composite fluorescent ceramic exhibits a broad emission band from 500 nm to 675 nm, which is attributed to the 5d → 4f transitions of Ce3+ and Eu2+ ions, respectively. By controlling the screen-printed times, the color coordinates of the composite fluorescent ceramics could be tuned from (0.3125, 0.2437) to (0.4106, 0.3824), and the correlated color temperature can vary from 3296 to 9689 K. In particular, the thermal stability of composite fluorescent ceramics is improved obviously after laser ablation. At 423 K, the luminescence intensity at 535 nm and 620 remains 91% and 94% of that at room temperature, respectively. Combining a 460 nm blue chip and the composite fluorescent ceramic, a white LED with CRI = 90, and the maximum luminous efficiency can be up to 148 lm/W. Our results indicate that Y2.84Lu0.1Al5O12: 0.06Ce3+/SrAlSiN3: Eu2+ composite fluorescent ceramics could be used in high-power white LEDs. 相似文献
9.
Zhengjuan Wang Xiaojun Wang Guohong Zhou Jianjun Xie Shiwei Wang 《Journal of the European Ceramic Society》2019,39(10):3229-3234
Highly transparent yttrium titanate (Y2Ti2O7) ceramics were fabricated by vacuum sintering using co-precipitated powders for the first time. The effects of the powder calcination temperature on the phase composition, morphology of the calcined powders, and on the microstructure and transmittance of the Y2Ti2O7 ceramics were investigated. When the calcination temperature was above 850 °C, pure phase Y2Ti2O7 nanopowders with high sintering activity were obtained. Transparent Y2Ti2O7 ceramics were obtained after vacuum sintered at 1600 °C for 6 h and annealed at 1100 °C for 5 h in air. The highest transmittance reached 73% at 1000 nm when the calcination temperature was 1150 °C. The measured refractive index of Y2Ti2O7 ceramics was higher than 2.24 at the wavelength range of 350–1000 nm, making it a promising candidate for optical devices. 相似文献
10.
《Journal of the European Ceramic Society》2020,40(4):1665-1670
Highly transparent Gd2Zr2O7 ceramic was fabricated by vacuum sintering using combustion synthesized nanopowder with mean particle size of about 80 nm. The morphology and structure were analyzed by X-ray diffractometer, scanning electron microscopy, Raman spectroscopy and transmission electronic microscopy. The Gd2Zr2O7 nanopowder and transparent ceramic are both in low ordered pyrochlore structure. The effects of sintering temperature on the density and transmittance of Gd2Zr2O7 ceramic were investigated, and the optimum sintering temperature (1825 °C) was obtained. Gd2Zr2O7 transparent ceramic sintered at 1825 °C for 6 h shows the highest transmittance of 77.3 % and the average grain size of about 80 μm. 相似文献
11.
《Ceramics International》2015,41(8):9577-9584
Mono-dispersed spherical Lu2O3:Eu (5 mol%) powders for transparent ceramics fabrication were synthesized by urea-based homogeneous precipitation technique. The effects of the doped-Eu3+ on the synthesis of Lu2O3:Eu particles were investigated in detail. The results show that the doping of Eu3+ ions into Lu system can significantly decrease the particle size of the resultant precursor spheres. Owing to the sequential precipitation in Lu/Eu system, there are compositional gradients within each of the resultant precursor spheres. Well dispersed, homogeneous and spherical/near spherical Lu2O3:Eu powders were obtained after calcination at 600–1000 °C for 4 h. The powder calcined at 600 °C shows better sintering behavior and can be densified into transparent ceramic after vacuum sintering at 1700 °C for 5 h. The luminescence properties of the obtained Lu2O3:Eu powder and transparent ceramic were also studied. 相似文献
12.
Impact of Eu3+ Dopants on Optical Spectroscopy of Ce3+: Y3Al5O12‐Embedded Transparent Glass‐Ceramics
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Yang Zhou Daqin Chen Wendong Tian Zhenguo Ji 《Journal of the American Ceramic Society》2015,98(8):2445-2450
Transparent glass‐ceramics containing Ce3+: Y3Al5O12 phosphors and Eu3+ ions were successfully fabricated by a low‐temperature co‐sintering technique to explore their potential application in white light‐emitting diodes (WLEDs). Microstructure of the sample was studied using a scanning electron microscope equipped with an energy dispersive X‐ray spectroscopy. The impact of co‐sintering temperature, Ce3+: Y3Al5O12 crystal content and Eu3+ doping content on optical properties of glass‐ceramics were systematically studied by emission, excitation spectra, and decay curves. Notably, the spatial separation of these two different activators in the present glass‐ceramics, where Ce3+ ions located in YAG crystalline phase while the Eu3+ ones stayed in glass matrix, is advantageous to the realization of both intense yellow emission assigned to Ce3+: 5d→4f transition and red luminescence originating from Eu3+: 4f→4f transitions. As a result, the quantum yield of the glass‐ceramic reached as high as 93%, and the constructed WLEDs exhibited an optimal luminous efficacy of 122 lm/W, correlated color temperature of 6532 K and color rendering index of 75. 相似文献
13.
Zhentao Wang Yanwei Zeng Chuanming Li Zhupeng Ye Liangliang Cao Yuan Zhang 《Ceramics International》2018,44(9):10328-10334
Gd3+ and Fe3+ co-doped cerium oxide electrolytes, Ce0.9Gd0.1‐xFexO2-δ (x?=?0.00, 0.01, 0.03, 0.05, 0.07, 0.10), were prepared by co-precipitation for ultrafine precursor powders and sintering for densified ceramic pellets. The crystal and microscopic structures were characterized by XRD, FESEM and Raman spectroscopy and their electrical properties were studied by AC impedance spectroscopy and the measurement of single cell's outputs. In comparison with Ce0.9Gd0.1O1.95, the ceramic pellets of Ce0.9Gd0.1‐xFexO2-δ with a relative density of 95% can be obtained after sintered at 1000?°C for 5?h, showing a remarkably enhanced sintering performance with a sintering temperature reduction of 500?°C, which might be ascribed to the highly activated migration of constituent species in the cerium oxide lattice doped with Gd3+ and Fe3+ions. Moreover, the electrical conductivity of Ce0.9Gd0.1‐xFexO2-δ can be significantly enhanced depending on the mole fraction x, with Ce0.9Gd0.07Fe0.03O1.95 exhibiting the highest electrical conductivity of 38 mS/cm at 800?°C, about 36% higher than that of Ce0.9Gd0.1O1.95 electrolyte sintered at 1500?°C for 5?h. So, The Gd3+ and Fe3+ co-doped cerium oxide would be an excellent candidate electrolyte for ILT SOFCs due to its prominent sintering performance and enhanced electrical conductivity. 相似文献
14.
《Ceramics International》2017,43(2):2165-2169
In this paper, (Lu,Gd)2O3:Eu ceramics were consolidated by the solid-state reaction method combined with vacuum sintering at 1820 °C for 10 h. It is found that the Gd2O3 incorporates well into the Lu2O3 lattices and forms a solid solution. Particularly, strong red emission of 5D0→7F2 transition of Eu3+ at 611 nm, matched well to the spectral sensitivity of typical CCD arrays, was observed in the photoluminescence and radioluminescence spectra. What's more, radioluminescence intensity of the 4f→4f transitions of Eu3+ reaches up to 10 times of bismuth germanium oxide (BGO) single crystal reference scintillator. Intensities of the radioluminescence and the integrated thermoluminescence versus temperatures, as well as the influence of annealing treatment on the thermoluminescence intensity, were also studied. We think that (Lu,Gd)2O3:Eu ceramic scintillators may have great potential in medical X-ray computed tomography (CT) due to their excellent properties. 相似文献
15.
Xiaorui Hou Shengming Zhou Wenjie Li Yukun Li 《Journal of the European Ceramic Society》2010,30(15):3125-3129
Transparent Y2O3 ceramics were fabricated by solid-state reaction using high purity Y2O3 and ZrO2 powder as starting material. The results indicated that ZrO2 additive can improve the transparency of Y2O3 ceramic greatly. The best transmittance appears with 3 at.% ZrO2 doped Y2O3 transparent ceramic with transmittance at 1100 nm of 83.1%, which is up to 98.6% of the theoretical value. The microstructure is uniform and no secondary phase is observed in the ceramic with the average grain size of 15 μm. The mechanism of ZrO2 improving the transparency of Y2O3 ceramic is analyzed in detail. On this basis, Yb3+ doped Y2O3 transparent ceramic was also fabricated and spectroscopic properties were investigated. 相似文献
16.
In this article, isocyanate was adopted to modify Y2O3 powder for the purpose of preparing transparent Y2O3 ceramics via gel casting. The modification could enhance the hydration resistance of Y2O3 powder through the steric hindrance effect. The coating mechanism can be proved by the infrared spectrum of the surface-modified Y2O3 powder. Modification could not only prevent Y2O3 particles from reacting with water, but also prevents agglomeration between particles. The viscosity of the slurry with a solid content of 52.7 vol% is only 0.48 Pa·s at the shear rate of 100 s−1, which is suitable for preparing high-density compacts by gel casting. The transmittance of the sample (1840°C × 8 h, 1 mm thickness) at 1100 nm reaches 75%. The microstructure of the sintered body is dense with the average grain size of 6.5 μm without obvious impurities nor pores. Five mol% ZrO2-doped Y2O3 transparent ceramic fairing with the diameter of 5 cm without defects was successfully fabricated by gel casting (52.7 vol% solid volume) and vacuum sintering (1840°C × 8 h). 相似文献
17.
《Journal of the European Ceramic Society》2017,37(8):2843-2848
Nanometric-sized gadolinia (Gd2O3) powders were obtained by applying solid-state displacement reaction at room temperature and low temperature calcination. The XRD analysis revealed that the room temperature product was gadolinium hydroxide, Gd(OH)3. In order to induce crystallization of Gd2O3, the subsequent calcination at 600 ∼ 1200 °C of the room temperature reaction products was studied. Calculation of average crystallite size (D) as well as separation of the effect of crystallite size and strain of nanocrystals was performed on the basic of Williamson-Hall plots. The morphologies of powders calcined at different temperatures were followed by scanning electron microscopy. The pure cubic Gd2O3 phase was made at 600 °C which converted to monoclinic Gd2O3 phase between 1400° and 1600 °C. High-density (96% of theoretical density) ceramic pellet free of any additives was obtained after pressureless sintering at 1600 °C for 4 h in air, using calcined powder at 600 °C. 相似文献
18.
Yihua Huang Dongliang JiangJingxian Zhang Qingling LinZhengren Huang 《Ceramics International》2011,37(8):3523-3529
Transparent Nd:Y2O3 ceramic was obtained by sintering mono-sized spherical powder. The powder was prepared by homogeneous precipitation method in aqueous media using urea to regulate the pH. The structure and morphology of the powder were investigated by TG-DTA, XRD, SEM and IR spectrum. The effect of aging temperature, time, and the concentration of urea, [Y3+], and [Nd3+] were investigated. Results showed that the obtained precursor was R2(OH)CO3·H2O (R = Y, Nd), and the least size of mono-sized spherical yttria particles was 72 nm by a microwave oven method after calcinations at 850 °C for 4 h. After dry press and CIP, the particles accumulated closely, and no defects can be detected in the green body. 相似文献
19.
《Journal of the European Ceramic Society》2019,39(2-3):635-640
5 at.% Yb:Y2O3 transparent ceramics were fabricated using vacuum sintering plus HIP. The ceramics doped with 1 at.% ZrO2 as the sintering additive were densified at 1700 °C in vacuum followed by HIPing at 1775 °C, while those without sintering additives were densified at 1520 °C in vacuum followed by HIPing at 1450 °C. After sintering, both ceramics had relatively high in-line transmittance. However, during laser experiments, the ZrO2-doped Yb:Y2O3 (Zr-YbY) ceramics were photodarkened when irradiated by 940 nm pump light. The discoloration might be attributed to the formation of Zr3+ color centers during lasing. In contrast, no photodarkening effect was detected in the pure Yb:Y2O3 ceramics without sintering additives (P-YbY). The P-YbY ceramics exhibited much higher lasing efficiency (17%) than the Zr-YbY ceramics (9%). To our best knowledge, it is the first time that the photodarkening effect was detected in rare-earth doped sesquioxide laser ceramics. 相似文献
20.
Li-Xiang Wu Lin-Lin Zhu Yang You Rui-Lin Lin Qing-Qing Liu Wei-Ming Guo Hua-Tay Lin Kevin Paul Plucknett 《Ceramics International》2021,47(1):935-942
Dense pressure-sintered reaction-bonded Si3N4 (PSRBSN) ceramics were obtained by a hot-press sintering method. Precursor Si powders were prepared with Eu2O3–MgO–Y2O3 sintering additive. The addition of Eu2O3–MgO–Y2O3 was shown to promote full nitridation of the Si powder. The nitrided Si3N4 particles had an equiaxial morphology, without whisker formation, after the Si powders doped with Eu2O3–MgO–Y2O3 were nitrided at 1400 °C for 2 h. After hot pressing, the relative density, Vickers hardness, flexural strength, and fracture toughness of the PSRBSN ceramics, with 5 wt% Eu2O3 doping, were 98.3 ± 0.2%, 17.8 ± 0.8 GPa, 697.0 ± 67.0 MPa, and 7.3 ± 0.3 MPa m1/2, respectively. The thermal conductivity was 73.6 ± 0.2 W m?1 K?1, significantly higher than the counterpart without Eu2O3 doping, or with ZrO2 doping by conventional methods. 相似文献