共查询到20条相似文献,搜索用时 15 毫秒
1.
Jie Fu 《Journal of the American Ceramic Society》1997,80(7):1901-1903
Fast lithium ion conducting glass-ceramics have been successfully prepared from the pseudobinary system 2[Li1+ x Ti2 Si x P3− x O12 ]-AlPO4 . The major phase present in the glass-ceramics was LiTi2 P3 O12 in which Ti4+ ions and P5+ ions were partially replaced by Al3+ ions and Si4+ ions, respectively. Increasing x resulted in a considerable enhancement in conductivity, and in a wide composition range extremely high conductivity over 10−3 S/cm was obtained at room temperature. 相似文献
2.
Emission properties and energy transfer of PbO–Bi2 O3 –Ga2 O3 –GeO2 glasses codoped with Tm3+ and Tb3+ ions were investigated. The 1.48-μm emission due to the Tm3+ :3 H4 →3 F4 transition can be used to amplify the S-band (1460–1530-nm) signal light. With Tb3+ addition, the lifetime and emission intensity of the Tm3+ :3 F4 level decreased sharply via the Tm3+ :3 F4 →Tb3+ :7 F0,1,2 energy transfer. Population densities of the 3 F4 and 3 H4 levels in Tm3+ calculated from rate equations clearly verified that population inversion in Tm3+ ions became possible with as little as 0.1 mol% of Tb3+ addition. 相似文献
3.
Xinmin Zhang Hong Chen Weijia Ding Hao Wu Jongsu Kim 《Journal of the American Ceramic Society》2009,92(2):429-432
Blue-emitting Ca2 B5 O9 Cl:Eu2+ phosphors have been synthesized by solid state reaction. The photoluminescence excitation (PLE) spectra show broad-band absorptions and can match the emission of near ultraviolet (n-UV) chip well. At lower Eu2+ concentration, the emission band can be resolved into two bands, which is assigned to the 5 d →4 f transition of Eu2+ ions substituting two different Ca2+ sites. At higher Eu2+ concentration, the energy transfer from Eu(1) to Eu(2) happens and is very efficient. At higher temperature the phosphor exhibits a lower temperature quenching effect. The fluorescence lifetimes are short enough for application in solid-state lighting. The electroluminescence spectrum indicates that the emission of chip can almost be absorbed by phosphor and down-converted into an intensive blue light. The chromaticity coordinates of fabricated light-emitting-diodes (LEDs) is very close to that of BaMgAl10 O17 :Eu2+ (BAM). Ca2 B5 O9 Cl:Eu2+ is a good blue component phosphor for n-UV excited solid-state lighting. 相似文献
4.
An Xie Ximing Yuan Yu Shi Fengxiang Wang Juanjuan Wang 《Journal of the American Ceramic Society》2009,92(10):2254-2258
A series of novel red phosphors LiEu1− x Bi x (WO4 )0.5 (MoO4 )1.5 ( x =0, 0.05, 0.10, 0.15, 0.20, 0.30, 0.40, and 0.50) were synthesized by the conventional solid-state reaction method. The spectrum and the crystal structure of the phosphors were characterized by Fluorescence spectrophotometry and X-ray diffraction, respectively. The photoluminescent results show that all samples can be excited efficiently by UV (396 nm) and blue (467 nm) light and that they emit red light at 615 nm with line spectra, which are coupled well with the characteristic emissions from UVLED and blue light-emitting diode (LED), respectively. There is an efficient energy transfer from Bi3+ to Eu3+ ions, leading to the emission intensity of Eu3+ being enhanced by 1.5 times, and even more when Bi3+ ions are introduced into LiEu (WO4 )0.5 (MoO4 )1.5 . The introduction of Bi3+ ions broadened the excitation band of the phosphor, and the optimum doping concentration is found to be 10 mol% of Bi3+ . 相似文献
5.
Junying Zhang Zhongtai Zhang Zilong Tang Yuanhua Lin 《Journal of the American Ceramic Society》2002,85(4):998-1000
A (Ce0.67 Tb0.33 )Mn x Mg1− x Al11 O19 phosphor powder was synthesized, using a simple sol–gel process, by mixing citric acid with CeO2 , Tb4 O7 , Al(NO3 )3 ·9H2 O, Mg(OH)2 ·4MgCO3 ·6H2 O, and Mn(CH3 COO)2 . The phosphor crystallized completely at 1200°C, and the phosphor particle size was between 1 and 5 μm. The excitation spectrum was characteristic of Ce3+ , while the emission spectrum was composed of lines from Tb3+ and Mn2+ . The Mn2+ gave a green fluorescence band, and concentration quenching occurred when x > 0.10. The luminescent properties of the phosphor were explained by a configurational coordinate model. 相似文献
6.
Daijitsu Harada Yukio Hinatsu Nobuyuki Masaki Akio Nakamura 《Journal of the American Ceramic Society》2002,85(3):647-652
Powder X-ray diffractometry (XRD) and 151 Eu Mössbauer spectroscopy were performed for samples prepared in the temperature range 1500–1500°C for the hafnia–europia (HfO2 –Eu2 O3 ) system Eu x Hf1− x O2− x /2 (0 ≤ x ≤ 1.0). The XRD results showed that two types of solid solution phases formed in the composition range 0.25 ≤ x ≤ 0.725: an ordered pyrochlore-type phase in the middle-composition range (0.45 < x < 0.575) and a disordered fluorite-type phase, enveloping the pyrochlore-type phase on both sides, in the composition ranges 0.25 ≤ x ≤ 0.40 and 0.60 ≤ x ≤ 0.725. 151 Eu Mössbauer spectroscopy sensitively probes local environmental changes around trivalent europium (Eu3+ ) caused by the formation of these solid solution phases. In addition to the broad, single Mössbauer spectra observed in this study for the Eu3+ , the values of isomer shift (IS) exhibited a pronounced minimum in the neighborhood of the stoichiometric pyrochlore phase ( x ≈ 0.5). Such IS behavior of Eu3+ was interpreted based on the XRD crystallographic information that the ordered pyrochlore phase has a longer (in fact, the longest) average Eu–O bond length than those of the disordered fluorite phases on both sides or the monoclinic (and C-type) Eu2 O3 at x = 1.0. 相似文献
7.
Shimin Liu Gaoling Zhao Wangle Ruan Zhiwang Yao Tingting Xie Ji Jin Hao Ying Jianxun Wang Gaorong Han 《Journal of the American Ceramic Society》2008,91(8):2740-2742
Eu2 O3 -doped aluminoborosilicate glasses were prepared in air at high temperature. Luminescence measurements were used to investigate a valence change from Eu3+ to Eu2+ ions in the aluminoborosilicate glasses. The results showed that the doped Eu3+ ions were partially reduced to Eu2+ in the Eu2 O3 :RO–Al2 O3 –B2 O3 –SiO2 (RO=CaO, SrO, BaO, Li2 O) glasses, but not in the Eu2 O3 :RO–Al2 O3 –B2 O3 –SiO2 (RO=Na2 O, K2 O) glasses. The changes of Eu reduction with different RO components were discussed with the variation of optical basicity of RO and with different valency of R cations. The effects of co-doping BaO and ZnO in aluminoborosilicate glasses on Eu reduction were also investigated and discussed. 相似文献
8.
Hui-Li Li Rong-Jun Xie Naoto Hirosaki Takashi Takeda Guo-Hong Zhou 《International Journal of Applied Ceramic Technology》2009,6(4):459-464
Eu2+ -doped M2 Si5 N8 (M=Ca, Sr, Ba) orange–red phosphors were successfully prepared by a simple, direct, and efficient solid-state reaction using air-stable MSi2 , Eu2 O3 , and α-Si3 N4 as the starting materials under N2 –H2 (5%) atmosphere. The influence of the type of the alkaline-earth ion on the phase structure and luminescence properties has been investigated. The results show that the synthesized powders have a single-phase crystal structure of M2 Si5 N8 for M=Ca, Sr, and a little amount of BaSi7 N10 impurity phase for M=Ba. Under the blue light excitation, M2 Si5 N8 :Eu2+ shows a typical broad band emission of Eu2+ ranging from orange to red (585–620 nm) depending on the type of M ion. The emission intensity, conversion efficiency, and thermal stability increase with the sequence of Ca2 Si5 N8 :Eu2+ has the highest application potential as a red conversion phosphor for white light-emitting diodes. 相似文献
9.
Sea-Fue Wang K. Koteswara Rao Yuh-Ruey Wang Yung-Fu Hsu Shih-Hsin Chen Yi-Ching Lu 《Journal of the American Ceramic Society》2009,92(8):1732-1738
A series of rare earth molybdates, Y2− x Eu x (MoO4 )3 for x =0.4, 0.8, 1.2, 1.6 and 2.0 were prepared by solid-state method and their crystal structures, photo luminescent characteristics were investigated. The powders are mainly studied for their red light emission efficiency under near UV excitation. The crystal structures of the powders were found to depend on annealing temperature and the yttrium concentration. Mixtures of monoclinic ( C 2 /c ) and orthorhombic ( Pba 2, Pbna ) structures were formed in varying proportions depending on the value of x and annealing temperatures (700°–800°C). The luminescence behavior depended on the resultant composition of the crystal phase and the Eu3+ concentration. The excitation spectra showed the characteristic and broad O→Mo charge transfer (CT) band of the MoO4 tetrahedra and the sharp intra-configurational 4 f –4 f transitions of Eu3+ in the host lattice. The integrated emission ratio (5 D0 →7 F2 /5 D0 →7 F1 ) of Eu3+ depends on the annealing temperature and reveals that the local site symmetry of Eu3+ ions decreases with increasing concentration of Eu3+ . The emission spectra obtained by exciting at 396 nm, gave highest red emission intensity for Y0.4 Eu1.6 (MoO4 )3 annealed at 700°C/6 h among this series of samples. 相似文献
10.
Kaustav Sinha Brett Pearson Said R. Casolco Javier E. Garay Olivia A. Graeve 《Journal of the American Ceramic Society》2009,92(11):2504-2511
A novel, integrated, fast, and inexpensive process for the preparation of dense Ba(1− x ) Eu x Al2 Si2 O8 thin ceramic specimens for damage sensor applications is reported. The processing approach involves a combination of combustion synthesis for the preparation of the powders and spark plasma sintering (SPS) for the consolidation of the specimens to densities close to 100% of relative density. The synthesis of the porous powders by combustion resulted in particle (agglomerate) sizes that were on average 421 nm, as determined from dynamic light scattering, and in the almost complete reduction of the initial Eu3+ activators to Eu2+ . The powders densified to grain sizes of around 250 nm due to a collapse of the porous powder structure and minimal grain growth during SPS. Thermal treatment of the powders and sintered specimens improved the intensity of the emissions at 373 and 745 nm and diminished the emission at 485 nm. The luminescence phenomena from the specimens were a result of two mechanisms: (1) the removal of strain in the lattice due to thermal treatment, and (2) a charge transfer mechanism between Eu2+ and Eu3+ . 相似文献
11.
Guorong Chen Yunxia Yang Donghui Zhao Fang Xia Stefania Baccaro Angelica Cecilia Martin Nikl 《Journal of the American Ceramic Society》2005,88(2):293-296
A group of terbium-doped heavy germanate glasses were studied. Glass matrices contained GeO2 , Gd2 O3 , BaO, and/or La2 O3 with the Tb3+ doping concentration ranging from 1 to 5 mol%. The transmission and radioluminescence spectra were measured and their correlations with glass composition are discussed. It is found that the UV cut-off edge of glass matrices is related to the content of the network modifier BaO as well as to the mixed rare earths effect, while the concentration of trapping sites existing in the glass network is essential to the radioluminescence properties of the glass. The latter is also associated with the content of the network modifier BaO that produces unsaturated nonbridging oxygens in the glass lattice. Another important mechanism influencing the luminescence process involves the enhanced energy transfer from Gd3+ ions to Tb3+ emission centers. A self-sensitizing effect of Tb3+ is observed in the Tb3+ concentration range studied, which contributes to some extent to the enhanced Tb3+ green emission. La2 O3 additions to the host glass play an active role of partitioning Tb3+ in the glass matrix, thereby showing an enhanced blue emission because of the reduced cross-relaxation probability between Tb3+ cations. 相似文献
12.
Li+ ions have been successfully doped into the La sites of (La0.95 Eu0.05 )2 Ti2 O7 nanocrystals through a facile citric acid sol–gel method. The doping concentration of Li+ ions can be as high as 15 mol%. Photoluminescence (PL) performances of the obtained samples have been investigated. The results showed that a doping with small number of Li+ ions improves the PL intensity of the synthesized La2 Ti2 O7 :Eu3+ nanophosphors. The highest emission intensity was observed using the formula of (La0.92 Eu0.05 Li0.03 )2 Ti2 O7 , whose brightness was increased by almost 20% in comparison with that of (La0.95 Eu0.05 )2 Ti2 O7 . 相似文献
13.
Tetsuya Kida Mohammed Mastabur Rahman Masamitsu Nagano 《Journal of the American Ceramic Society》2006,89(5):1492-1498
Eu2+ -doped CaMgSi2 O6 phosphor was prepared by depositing mixed hydroxides of Ca, Mg, and Eu over spherical SiO2 particles (300 nm) pre-coated with polycations (polyethyleneimine), followed by calcination at 1200°C in a reducing atmosphere. The prepared phosphor showed intense blue emission, ascribable to the 4f7 -4f6 5d transition of Eu2+ . In contrast, the luminescence intensity of the phosphor was considerably decreased when prepared without polycations. It was suggested that negatively charged hydroxides are deposited on positively charged SiO2 surfaces pre-coated with polycations through electrostatic self-assembly interaction. On calcination, the hydroxide shells react with the SiO2 cores to produce Eu2+ :CaMgSi2 O6 . 相似文献
14.
The syntheses and the results of unit-cell determinations ofBa3 V4 O13 and the two forms (low- and high-temperature) of Ba3 P4 O13 are presented. Ba3 V4 O13 crystallizes in the monoclinic system, space group Cc or C2/c with unit-cell dimensions a=16.087, b=8.948, c=10.159 (x10nm), β=114.52° Low-Ba3 P4 O13 crystallizes in the triclinic system, space group P1 or P1 with unit-cell dimensions a=5.757, b=7.243, c=8.104 (x10 nm) α=82.75°, β=73.94°, γ=70.71°. Low-Ba3 P4 O13 transforms at 870°C into high-Ba3 P4 O13 which crystallizes in the orthorhombic system, space group Pbcm (No. 57) (or Pbc2, No. 29) with unit-cell dimensions a =7.107, b=13.883, c=19.219 (x10 nm). No relations have been found between the structures of the tribarium tetravanadate and the tribarium tetraphosphate. 相似文献
15.
Shingo Ishida Feng Ren Nobuyuki Takeuchi 《Journal of the American Ceramic Society》1993,76(10):2644-2648
A new yellow pigment with the pyrochlore structure Cax Y2− x V x Ti2− x O7 was prepared as a substitute for the decreasing variety of available yellow ceramic pigments due to the severe regulation of toxic lead and cadmium. The solubility limit of vanadium in this pigment was found to be 1.5 wt% as V2 O5 or 0.13 as x in the above formula expression. Characterization of vanadium in the vanadium pyrochlore yellow pigment by electron spectroscopy for chemical analysis and electron spin resonance showed that the oxidation state of vanadium was V5+ and its yellow color mostly originated from V5+ substituted for Ti4+ . Comparison of color characteristics of Cax Y2− x V x Ti2− x O7 with those of commercial V–SnO2 and V–ZrO2 revealed that Ca x Y2− x V x Ti2− O7 had better color strength and brightness than the commercial pigments. 相似文献
16.
Anal Tarafder Kalyandurg Annapurna Reenamoni Saikia Chaliha Vidya Sagar Tiwari Pradeep Kumar Gupta Basudeb Karmakar 《Journal of the American Ceramic Society》2009,92(9):1934-1939
We report here the processing and properties of transparent glass and glass–ceramic nanocomposites in the Li2 O–Ta2 O5 –SiO2 –Al2 O3 system in the presence of Eu2 O3 as luminescent probe. The formation of the LiTaO3 crystal phase, the crystallite size, and the morphology with the progression of heat treatment have been examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transformed infrared reflectance spectroscopy measurements. The crystallite sizes obtained from XRD and TEM are found to increase with heat-treatment time and vary in the range of 2–20 nm. The measured photoluminescence spectra exhibit emission transitions of 5 D0,1 →7 F j ( j =0, 1, 2, 3, and 4) of Eu3+ ions. From the nature of the emission transitions, the site symmetry in the vicinity of Eu3+ ions has been found to be near C3v in the glass–ceramic nanocomposites. An inverse correlation has been observed between the asymmetric ratio ( I ED / I MD ) of Eu3+ ions and the dielectric constant (ɛr ), with an increase in the heat-treatment time of glass, which is caused by the dipole–dipole interaction. 相似文献
17.
C. C. Khaw C. K. Lee Z. Zainal G. C. Miles A. R. West 《Journal of the American Ceramic Society》2007,90(9):2900-2904
The subsolidus phase diagram of the system Bi2 O3 –ZnO–Ta2 O5 in the region of the cubic pyrochlore phase has been determined at 1050°C. This phase forms a solid solution area that includes the ideal composition P, Bi3 Zn2 Ta3 O14 ; possible solid solution mechanisms are proposed, supported by density measurements of Zn-deficient solid solutions. The general formula of the solid solutions is Bi3+ y Zn2− x Ta3− y O14− x − y , based on the creation of Zn2+ , O2− vacancies in Zn-deficient compositions and a variable Bi/Ta ratio. 相似文献
18.
Jianrong Qiu Katsuhisa Tanaka Kazuyuki Hirao 《Journal of the American Ceramic Society》1997,80(10):2696-2698
Fluoroaluminate glasses containing various concentrations of Eu2+ were prepared under a reducing atmosphere for the present study, and the wavelength dependence of the Faraday rotation angle was examined. The magnitude of the Verdet constant (Vc ) increased as the concentration of Eu2+ increased. In addition, the Verdet constant of glasses containing 5 cat.% Eu2+ was larger than that of fluoroaluminate glasses containing the same concentration of Tb3+ in the wavelength region from 400 to 600 nm. The effective transition wavelength, λt , for glasses containing Eu2 + as well as those containing Tb3 + was evaluated based on the Van Vleck and Hebb theory. Factors dominating the Verdet constant of those glasses are discussed in this report. 相似文献
19.
HIROTOSHI OSHIMA 《Journal of the American Ceramic Society》1980,63(9-10):504-508
Phase relations in the quasi-ternary system MgO-V2 O3 -VO2 at 1200°C were studied using the quenching technique under controlled O2 atmospheres. A new phase of a type z VO y Mg2− x V1+ x O4 (0< x <1, y ≥1.5, z >0) was found with a compositional region along the MgV2 O4 -Mg2 VO4 join. Equilibrium P O 2 observed for Mg2− x V1+ x O4 is quite different from that for V n O2 n -1 with an equal ratio of V3+ /V4+ , corresponding to the V3+ stabilities in two types of compounds. Thus, the phase relations in the ternary system were constructed on a conventional triaxial diagram as a function of P O2 . 相似文献
20.
Michael Rozumek Peter Majewski Heike Schluckwerder Fritz Aldinger Klaus Künstler Gerhard Tomandl 《Journal of the American Ceramic Society》2004,87(9):1795-1798
Ceramics of the melilite-type compound La1+ x Sr1− x Ga3 O7−δ were prepared by conventional ceramic processing. Samples prepared represented the entire homogeneity region of the phase (i.e., x =−0.15 to 0.60). Electrochemical characterization under variable temperature and atmospheric conditions in the vicinity of air entailed four-point direct-current conductivity measurements and electromotive force measurements. La1+ x Sr1− x Ga3 O7−δ samples exhibited a p -type behavior with generally increased conductivity with increased substitution of lanthanum for strontium, which reached a saturation value of ∼10−1 S·cm−1 at 950°C. 相似文献