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《Materials Research Bulletin》2006,41(2):225-231
Hydrogarnet Sr3Al2(OH)12 (SAH) has been obtained from hydrothermal systems with a wide range of pH values under mild conditions. The influence of reaction conditions on the formation of various phases has been considered. The addition of sodium hydroxide can favor the yield of pure SAH phase. Stoichiometric Sr3Al2O6 (SAO) has been prepared from SAH through thermal decomposition over 600 °C for 4 h. SAO can act as a red phosphor host with doping of Eu3+ ions. The Eu3+ ions as activators can be introduced directly under hydrothermal conditions before thermal decomposition. 相似文献
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Wenying Zhang Fang Liu Suqin Feng Shangfu Hao Yongchun Xu Jinyu Guan 《Journal of Materials Science: Materials in Electronics》2014,25(5):2355-2358
Sr3Al2O6:Ce3+ powders were synthesized using a solid state reaction method in air with addition of H3BO3. The effects of Ce3+ dopant concentrations and the weight ratio (wt) of H3BO3 to total raw materials weight on the formation of Sr3Al2O6:Ce3+ samples were investigated. Single-phase and well-crystallized Sr3Al2O6:Ce3+ samples can be obtained when the addition of H3BO3 is lower than 7 wt%. The excitation spectrum indicates that Sr3Al2O6:Ce3+ phosphor powders exhibit two excitation bands centered at 345 and 462 nm. The emission spectrum shows that Sr3Al2O6:Ce3+ phosphor powders exhibit an emission band peaked at 536 nm when excited at 462 nm. Sr3Al2O6:Ce3+ sample at the Ce3+ concentration of 5 mol% shows the strongest emission intensity. The addition of H3BO3 has obvious influence on phase and emission intensity of Sr3Al2O6:Ce3+ phosphors. The results show that the Sr2.95Ce0.05Al2O6 sample with the 7 wt% addition of H3BO3 has the highest emission intensity and the longest lifetime. 相似文献
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G. C. Mishra A. K. Upadhyay R. S. Kher S. J. Dhoble 《Journal of Materials Science》2012,47(2):898-901
Undoped and rare earth (RE = Ce, Dy, and Eu) doped GdCa4O(BO3)3 phosphors were synthesized by solid-state diffusion technique. Formation of the sample was confirmed by taking X-ray diffraction
(XRD) pattern of the sample. Photoluminescence (PL) emission spectrum showed characteristic emission of RE doped in the GdCa4O(BO3)3 sample. It is observed that doping of RE ion initially enhanced the TL yield, attained an optimum TL for a particular concentration
of dopant (i.e., 0.5 mol%) then decreased with further increase in dopant concentration for all the samples. We found that
Ce is the best activator for enhancing the TL yield in GdCa4O(BO3)3 system. Fading of TL intensity of the sample was studied and it is found that fading of the TL is about 5% over the period
of 15 days. The simple glow curve, linear response to γ-ray dose and less fading; makes the GdCa4O(BO3)3:Ce(0.5 mol%) phosphors a suitable candidate for TL dosimetry. 相似文献
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《中国计量学院学报》2017,(4):533-538
实验通过高温固相法合成了不同气氛条件下的BaZn_2(BO_3)_2荧光粉.在空气气氛条件下制备的BaZn_2(BO_3)_2样品,发射黄色的荧光,峰位在543nm处,这是由颗粒中单个带负电荷的氧填隙离子O-i中心捕获价带上的光生空穴,与导带上落下的光生电子辐射复合产生的.在氮氢还原气氛条件下的BaZn_2(BO_3)_2样品,发射绿色的荧光,峰位在500nm处,这是由于在颗粒中光生电子经过无辐射跃迁,落入被单一电离的氧空位缺陷V*o,再由缺陷回到靠近价带,与光生空穴复合产生可见光的发射.BaZn_2(BO_3)_2荧光粉紫外波段有很强的吸收,并且荧光衰减寿命和稀土元素掺杂的荧光粉寿命相当.因此BaZn_2(BO_3)_2荧光粉在用于白光LED时,将会具有广泛的应用前景与潜在的商业价值. 相似文献
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ZIVAR GHEZELBASH DAVOUD ASHOURI SAMAN MOUSAVIAN AMIR HOSSEIN GHANDI YAGHOUB RAHNAMA 《Bulletin of Materials Science》2012,35(6):925-931
Organic–inorganic hybrid materials consisting of inorganic materials and organic polymers are a new class of materials, which have received much attention in recent years. In the present investigation, at first, the surface of nano-alumina (Al 2 O 3 ) was treated with a silane coupling agent of $\boldsymbol{\gamma} $ -aminopropyltriethoxysilane (KH550), which introduces organic functional groups on the surface of Al 2 O 3 nanoparticles. Then fluorinated polyimide (PI) was synthesized from 4,4 ′ -(hexafluoroisopropylidene) diphthalic anhydride and 4,4 ′ -diaminodiphenylsulfone. Finally, PI/modified Al 2 O 3 nanocomposite films having 3, 5, 7 and 10% of Al 2 O 3 were successfully prepared by an in situ polymerization reaction through thermal imidization. The obtained nanocomposites were characterized by fourier transform infrared spectroscopy, thermogravimetry analysis, X-ray powder diffraction, UV-Vis spectroscopy, field emission scanning electron microscopy and transmission electron microscopy. The results show that the Al 2 O 3 nanoparticles were dispersed homogeneously in PI matrix. According to thermogravimetry analysis results, the addition of these nanoparticles improved thermal stability of the obtained hybrid materials. 相似文献
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《Advanced Powder Technology》2020,31(6):2366-2378
Lanthanum hydroxycarbonate (LaOHCO3) spheres were synthesized with an experimental investigation on the role of capping agent by using homogeneous precipitation method. The prepared LaOHCO3 was analyzed using XRD, FT-IR, SEM, TGA and photoluminescence (PL) to understand its formation. From the XRD spectrum, variation in the crystallite size, strain distributions, dislocation density and the number of unit cells in the crystal were obtained by using Debye Scherer’s relation, Williamson-hall and Stoke Wilson formula. From the results, various intermediate products and morphology were observed before the formation of LaOHCO3 sphere if citric acid (CA) was used as a capping agent. In contrast, there is no intermediate product formation in the absence of CA. By using fluorescence spectrophotometry, the PL spectrum of LaOHCO3 and the relation between crystalline size and emission intensity of the PL spectrum was studied in the presence and absence of CA with time. For both the cases, the emission was observed at the wavelengths of 420, 438 and 465 nm at excitation wavelength of 365 nm but the only variation in the emission intensity was observed due to change in the morphology and crystalline size of LaOHCO3. In the absence of CA, the relation between emission intensity and crystalline size was directly proportional to each other with time. In contrast, the relationship of the prepared LaOHCO3 with CA was contrary due to the variation in the morphology and crystalline size. 相似文献
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Composites consisting of Al-Zn/Al2O3 have been synthesized using high energy mechanical milling. High energy ball milling increases the sintering rate of the composite powder due to increased diffusion rate. Owing to the finer microstructure, the hardness of the sintered composite produced by using the mechanically milled nanocomposite powder is significantly higher than that of the sintered composite produced by using the as-mixed powder. The mean crystallite size of the matrix has been determined to be 27 nm by Scherrer equation using X-ray diffraction data. The powders have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and differential thermal analysis (DTA). The effect of high-energy ball milling and subsequent annealing on a mixture of Al and ZnO has also been investigated. DTA result show that the reaction temperature of Al-ZnO decreases with the increase in the ball milling time. 相似文献
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C. Simon R. Bredesen H. Grøndal A. G. Hustoft E. Tangstad 《Journal of Materials Science》1995,30(21):5554-5560
The sol-gel method has been used to synthesize alumina powder with high surface area from boehmite. The characteristics of the final powder product have been systematically studied in light of the preparation method and starting materials by fractional factorial design. The results show that the type of precursor and pH of the precursor sol are the most important parameters for the textural properties of the calcined alumina powder. When the calcination temperature is increased the type of precursor loses its significance, while the pH still has decisive importance after calcination at 1000°C, on pore volume and surface area. There is also a significant combined effect of several parameters on the surface area and the pore volume. The electrophoretic mobility, agglomerate size and size distribution have been determined as a function of the pH for one type of boehmite sol. The relation between characteristics of the precursor and powder properties is clearly emphasized. 相似文献
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溶胶-凝胶法合成Sr2SiO4:Sm3+及其发光性能 总被引:1,自引:0,他引:1
采用溶胶-凝胶法合成了Sr<,2>SiO<,4>:Sm<,3+>红色荧光粉,用XRD、SEM、PL对样品进行了结构、型貌及发光性能表征.结果表明,所得样品为单斜晶系结构,呈粒径为0.1~0.3μm、1μm左右长的纤维状小颗粒;在波长402nm的紫外激发下,样品发射光谱由位于红橙区的3个主要荧光发射峰组成,峰值分别位于568,605nm和651nm,对应了Sm<'3+>的<'4>G<,5/2>→<'6>H<,5/2>,<'4>G<,5/2>→<'6>H<,7/2>和<'4>G<,5/2>→<'6>H<,9/2>特征跃迁发射,605nm的发射最强,是一种适用于白光LED的红色荧光粉. 相似文献
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CaAl2−yO4:yMn4+ (y = 0–1.6 mol%) phosphors are synthesized by a solid-state reaction method in air, and their crystal structure and luminescence property are investigated. To compare luminescence property, CaAl3.99O7:1%Mn4+ and SrAl1.99O4:1%Mn4+ phosphors are also synthesized at the same condition. Broad band excitation spectra are observed within the range 220–550 nm, and emission spectra cover from 600 to 720 nm with the strongest emission peak at ∼658 nm owing to the 2E → 4A2 transition of Mn4+ ion. The influence of crystal field to luminous intensity is discussed, and the possible luminous mechanism of Mn4+ ion is explained by using energy level diagram of Mn4+ ion. CaAl1.99O4:1%Mn4+, CaAl3.99O7:1%Mn4+, and SrAl1.99O4:1%Mn4+ phosphors under excitation 325 nm light emit red light, and their CIE chromaticity coordinates are (0.7181, 0.2813), (0.7182, 0.2818), and (0.7198, 0.2801), respectively. These contents in the paper are helpful to develop novel and high-efficient Mn4+-doped phosphor for white LEDs. 相似文献
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Phosphors of La2TeO6 doped with Eu3+ ions have been synthesized by the oxidation of the corresponding rare-earths oxytellurides of formula La2−xEuxO2Te (x = 0.02, 0.06, and 0.1) at 1050 K. Powder X-ray diffraction confirms that the as prepared materials consist of the orthorhombic La2TeO6 as main phase. The photoluminescence (PL) of red-emitting La2−xEuxTeO6 powder phosphors is reported. The emission spectrum, exhibits an intense emission peak due to 5D0 → 7F2 transition at 616 nm, which indicates that the Eu3+ ion occupies a non-centrosymmetric site in the host lattice. These materials could find application for use as lamp phosphors in the red region. 相似文献
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Aoyang Yu Dong Zhang Yafei Hu Ruiqin Yang 《Journal of Materials Science: Materials in Electronics》2014,25(10):4434-4438
Sr3Al2O6:Eu2+, Dy3+ phosphors were synthesized by the polymer precursor method. The X-ray powder diffraction patterns show that the samples have a cubic structure with a space group of Pa3. In the excitation spectrum, the phosphors show a wide absorption in the UV region from 250 to 450 nm, which corresponds to the crystal field splitting of the Eu2+ d-orbital. All the emission spectrum of Sr3Al2O6:Eu2+, Dy3+ phosphors show the broad band emission peaked at about 518 nm, which can be ascribed to the typical 4f65d1 → 4f7 transitions of Eu2+ ions. And the best dopant concentration of Dy3+ ions for Sr3Al2O6:2 mol%Eu2+, xDy3+ phosphors is 2 mol%. The excitation wavelengths have no influences on emission peaks, but have clear influences on emission intensities. 相似文献
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在微波场作用下合成了Sr2Al6O11:Eu2 x%(质量分数)(H3BO3)(x=0、1.5、3、5、7、9)系列蓝色光致发光材料.X射线粉末衍射(XRD)结果表明,未加硼酸作助熔剂时,产品的主相为SrAl2O4,硼酸在x=1.5~9之间产品的主相都为Sr2Al6O11.扫描电镜(SEM)观测结果:适量硼酸的加入有助于晶体的形成,硼酸的量为0时,产物为颗粒,硼酸量为x=1.5时,开始出现棒状晶体,当硼酸量为x=5时,产物主要为棒状晶体,当硼酸量x>7时,产品明显团聚.荧光光谱显示:随硼酸量的增加,产品发光强度先增强后减弱,硼酸加入量为x=7,发光强度最高.Eu2 在Sr2Al6O11中存在两个发光中心,发射峰分别位于456.7nm(Eu2 1)和483.4nm(Eu2 2).当硼酸量>7%(质量分数)时,发射峰红移,归因于硼酸对两种位置Eu2 的发光性能有不同的影响. 相似文献