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1.
REVO4‐Based Nanomaterials (RE = Y,La, Gd,and Lu) as Hosts for Yb3+/Ho3+, Yb3+/Er3+, and Yb3+/Tm3+ Ions: Structural and Up‐Conversion Luminescence Studies
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Artur Tymiński Tomasz Grzyb Stefan Lis 《Journal of the American Ceramic Society》2016,99(10):3300-3308
Rare‐earth vanadates of the form REVO4 (RE = Y, La, Gd, and Lu) doped by Yb3+/Ho3+, Yb3+/Er3+, or Yb3+/Tm3+ lanthanide ions were successfully synthesized using the sol–gel method and annealing at 600°C in an air atmosphere. The structure and morphology of the prepared nanocrystals were investigated by X‐ray diffraction, thermogravimetric analysis, transmission electron microscopy, and energy‐dispersive X‐ray spectroscopy. All prepared materials were homogenous and had nanosized dimensions. Their elemental compositions were confirmed by optical emission spectrometry. Spectroscopic analysis of the materials was carried out by measuring excitation and emission spectra, luminescence decays, and dependence between the intensity of the luminescence and the laser energy. Following effective excitation by NIR radiation, Ln3+ co‐doped vanadate matrices exhibited a strong up‐conversion (UC) luminescence. Differences in spectroscopic properties between monoclinic LaVO4 and tetragonal YVO4, GdVO4, or LuVO4 doped by Ln3+ ions were observed, indicating the influence of the crystal structure on the UC emission. Drawing conclusions from these spectroscopic investigations, the UC mechanisms were proposed, including energy‐transfer processes between Yb3+ ions and emitting ions. 相似文献
2.
Ting Li Chongfeng Guo Puju Zhao Lin Li Jung Hyun Jeong 《Journal of the American Ceramic Society》2013,96(4):1193-1197
Using a modified sol–gel method, LiLa(MoO4)2: Tm3+/Ho3+/Yb3+ phosphors with tailorable up‐conversion (UC) emission colors were prepared. Under the excitation of a 980 nm laser diode, up‐conversion red and green emissions in Ho3+/Yb3+ co‐doped and blue emission in Tm3+/Yb3+ co‐doped LiLa(MoO4)2 were observed, respectively. The intensities of the RGB (red, green, and blue) emissions could be controlled by varying concentrations of Tm3+ or Ho3+, and the optimal composition was also determined. In Tm3+/Ho3+/Yb3+ co‐doped LiLa(MoO4)2, the UC emission colors could be tuned from blue through white to yellow by adjusting the concentrations of Tm3+ or Ho3+. The UC excitation mechanisms were also investigated based on the power dependence of UC luminescence intensity. 相似文献
3.
Efficient dual‐mode up‐conversion and down‐shifting emission in β‐NaYF4:Yb3+,Er3+ microcrystals via ion exchange
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Shaohua Fan Shikai Wang Hongtao Sun Shiyu Sun Guojun Gao Lili Hu 《Journal of the American Ceramic Society》2017,100(7):3061-3069
We report efficient dual‐mode up‐conversion (UC) and down‐shifting (DS) emission in a single Yb3+/Er3+‐co‐doped β‐NaYF4 microcrystals with controlled morphology and size via a simple Na+ ion‐exchange modification (IEM) method. IEM well preserves the crystal structure and monodispersed morphology of hydrothermal‐synthesized β‐NaYF4. Meanwhile, IEM gives rise to the significant enhancement of UC emission intensity up to 3800 times and strongly enhanced DS emission intensity of Er3+ and Yb3+ by several times in β‐NaYF4:Yb3+,Er3+ microcrystals. IEM also strongly prolongs the DS emission lifetimes of Er3+ and Yb3+ in visible and near‐infrared region. The enhanced UC and DS emission intensities and prolonged lifetimes in β‐NaYF4:Yb3+,Er3+ are mainly ascribed to the dispersing of localized Yb3+ and Er3+ clusters during IEM. 相似文献
4.
Preparation,Structure, and Up‐Conversion Luminescence of Yb3+/Er3+ Codoped SrIn2O4 Phosphors
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Ming Guan Hong Zheng Lefu Mei Maxim S. Molokeev Jing Xie Tao Yang Xiaowen Wu Saifang Huang Zhaohui Huang 《Journal of the American Ceramic Society》2015,98(4):1182-1187
SrIn2O4, which shows lower phonon energy than CaIn2O4, is not only a good photocatalyst but also can be an excellent up‐conversion (UC) host to exhibits UC luminescence. In this work, Yb3+ and/or Er3+ doped SrIn2O4 phosphors were synthesized, and their UC luminescence properties were studied and compared with those in the CaIn2O4 host. The structure of SrIn2O4: 0.01Er3+ and SrIn2O4: 0.1Yb3+/0.01Er3+ samples were refined by the Rietveld method and found to that SrIn2O4: 0.1Yb3+/0.01Er3+ showed increasing unit cell parameters and cell volume, indicating In3+ sites were substituted successfully by Yb3+ and/or Er3+ ions. From the UC luminescence spectra and diffuse reflection spectra, Er3+‐doped SrIn2O4 showed very weak luminescence due to ground state absorption of Er3+; Yb3+/Er3+ codoped SrIn2O4 presented strong green (550 nm) and red (663 nm) UC emissions which were assigned to energy transfer from Yb3+ transition 2F7/2→2F5/2 to the Er3+ transition 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2. Comparing with CaIn2O4, Yb3+/Er3+ codoped SrIn2O4 showed obvious advantages with higher UC luminescent intensity. The pumping powers study showed that UC emissions in Yb3+/Er3+ codoped SrIn2O4 were attributed to energy transfer of Yb3+→Er3+ with a two‐photon process. The possible UC luminescent mechanism of Yb3+/Er3+‐doped SrIn2O4 was discussed. 相似文献
5.
Wide‐range thermometry based on green up‐conversion luminescence of K3LuF6:Yb3+/Er3+ bulk oxyfluoride glass ceramics
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JiangKun Cao FangFang Hu LiPing Chen Hai Guo Changkui Duan Min Yin 《Journal of the American Ceramic Society》2017,100(5):2108-2115
Yb3+/Er3+ ions codoped bulk glass ceramics (GC) with embedded monoclinic K3LuF6 nanocrystals are reported for potential temperature‐sensing application by using the fluorescence intensity ratio method. Such GC with good transparency and enhanced up‐conversion were prepared by the simple conversional melt‐quenching method and subsequent annealing process. Optical, structural, and temperature‐sensing up‐conversion properties were characterized systematically. Optical spectroscopy analysis confirms the incorporation of Yb3+/Er3+ into the K3LuF6 crystalline lattice, resulting in enhanced up‐conversion luminescence. Compared to other Er3+‐doped typical systems, Er3+ ions in K3LuF6 GC present large energy gap (870 cm?1) and high relative sensitivity (37.6 × 10?4 K?1 at 625 K), revealing that K3LuF6:Yb3+/Er3+ GC can be excellent candidates for optical thermometers. 相似文献
6.
Jianxiong Zhao Qinyuan Zhang Ni Qin Baojun Li Dinghua Bao 《Journal of the American Ceramic Society》2013,96(4):1214-1219
The color‐tunable up‐conversion (UC) emission and infrared photoluminescence and dielectric relaxation of Er3+/Yb3+ co‐doped Bi2Ti2O7 pyrochlore thin films prepared by a chemical solution deposition method have been investigated. The pyrochlore phase structure of Bi2Ti2O7 can be stabilized by Er3+/Yb3+ co‐doping. Intense color‐tunable UC emission and infrared photoluminescence can be detected on the thin films excited by a 980 nm diode laser. Two UC emission bands centered at 548 and 660 nm in the spectra can be assigned to 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ ions, respectively. A Stokes infrared emission centered at 1530 nm is due to 4I13/2 → 4I15/2 transition of Er3+ ions. The dependence of UC emission intensity on pumping power indicates that the UC emission of the thin films is a two‐photon process. The thin films also exhibit a relatively high dielectric constant and a low dissipation factor as well as a good bias voltage stability. Temperature‐ and frequency‐dependent dielectric relaxation has been confirmed. This study suggests that Er3+/Yb3+ co‐doped Bi2Ti2O7 thin films can be applied to new multifunctional photoluminescence dielectric thin‐film devices. 相似文献
7.
Upconversion Luminescence and Energy‐Transfer Mechanism of NaGd(MoO4)2: Yb3+/Er3+ Microcrystals
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Anming Li Dekang Xu Yueli Zhang Hao Lin Shenghong Yang Zhenqiang Chen Yuanzhi Shao 《Journal of the American Ceramic Society》2016,99(5):1657-1663
Uniform and well‐crystallized NaGd(MoO4)2: Yb3+/Er3 + microcrystals with tetragonal plate morphology were synthesized by a facile hydrothermal method. The structure and phase purity of the samples were identified by powder XRD analysis. The steady‐state and transient luminescence spectra were measured and analyzed. Under 980 nm excitation, intense green luminescence at 531 and 553 nm, and red luminescence at 657 and 670 nm were observed. The optimum doping concentrations for Yb3+ and Er3+ are determined to be 20% and 1% in NaGd(MoO4)2 tetragonal plate microcrystals. With increasing Yb3+ doping concentrations, the total integral emission intensities increase first and then decrease. The red/green intensity ratio of NaGd(MoO4)2: Yb3+/Er3+ microcrystals increases from 0.4 to 1.0 with the increase in Yb3+ concentrations. Based on the energy level diagram, the energy‐transfer mechanisms are investigated in detail according to the double logarithmic plot of upconversion intensities versus pump powers. The energy‐transfer mechanisms for green and red upconversion luminescence are ascribed to two‐photon processes at lower Yb3+ concentrations, and involve high‐Yb3+‐induced one‐photon processes at higher Yb3+ concentrations. For the red upconversion luminescence, energy back‐transfer process, that is, 4S3/2 (Er3+) + 2F7/2 (Yb3+) → 4I13/2 (Er3+) + 2F5/2 (Yb3+), is dominant at higher Yb3+ concentrations. Theoretical model of the energy‐transfer mechanisms based on rate equations is established, which agrees well with the experimental results. 相似文献
8.
Thermal effects of Er3+/Yb3+‐doped NaYF4 phosphor induced by 980/1510 nm laser diode irradiation
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Hong Wang Xiumei Yin Mingming Xing Yao Fu Ying Tian Xin Feng Tao Jiang Xixian Luo 《Journal of the American Ceramic Society》2018,101(2):865-873
The thermal effects of Er/Yb‐doped NaYF4 phosphor induced by 980/1510 nm laser diode irradiation were intuitively and contrastively investigated using an infrared thermal imaging technology with real‐time online monitoring. The Yb3+/Er3+ codoped materials have strong thermal effects and high‐temperature elevation under 980 nm irradiation. However, the severe thermal effects of materials with higher Er3+ ion doping concentration are remarkably attributed to the cross relaxation between the Er3+ ions under 980 nm irradiation. The energy transfer between Er3+ and Yb3+ ions in Er3+/Yb3+‐codoped materials also contributes to the thermal effects under 1510 nm laser diode irradiation. Under the same testing conditions, the temperature elevation ?T of samples induced by 1510 nm laser diode irradiation is lower than that induced by 980 nm laser diode irradiation. The temperature rising rate and elevation ?T value of samples depend on the ion doping concentration and power density of the laser diode excitation. The internal temperature of the samples exhibits deep temperature gradient under 980/1510 nm laser diode irradiation. By comparing the two kinds of thermometry methods, the temperature value calculated by fluorescence intensity ratio is almost similar to that obtained through infrared thermal imaging technology under higher excitation power pumping. 相似文献
9.
《Ceramics International》2020,46(11):18614-18622
Studies on lanthanide ions doped upconversion nanomaterials are increasing exponentially due to their widespread applications in various fields such as diagnosis, therapy, bio-imaging, anti-counterfeiting, photocatalysis, solar cells and sensors, etc. Here, we are reporting upconversion luminescence properties of NaBi(MoO4)2:Ln3+, Yb3+ (Ln = Er, Ho) nanomaterials synthesized at room temperature by simple co-precipitation method. Diffraction and spectroscopic studies revealed that these nanomaterials are effectively doped with Ln3+ ions in the scheelite lattice. DR UV–vis spectra of these materials exhibit two broad bands in the range of 200–350 nm correspond to MoO42− charge transfer, s-p transition of Bi3+ ions and sharp peaks due to f-f transition of Ln3+ ions. Upconversion luminescence properties of these nanomaterials are investigated under 980 nm excitation. Doping concentration of Er3+ and Yb3+ ions is optimized to obtain best upconversion photoluminescence in NaBi(MoO4)2 nanomaterials and is found to be 5, 10 mol % for Er3+, Yb3+, respectively. NaBi(MoO4)2 nanomaterials co-doped with Er3+, Yb3+ exhibit strong green upconversion luminescence, whereas Ho3+, Yb3+ co-doped materials show strong red emission. Power dependent photoluminescence studies demonstrate that emission intensity increases with increasing pump power. Fluorescence intensity ratio (FIR) and population redistribution ability (PRA) of 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 transitions of Er3+ increases with increasing the Yb3+ concentration. Also, these values increase linearly with increasing the pump power up to 2 W. It reveal that these thermally coupled energy levels are effectively redistributed in co-doped samples due to local heating caused by Yb3+. 相似文献
10.
《Ceramics International》2016,42(13):14710-14715
Usually, Er3+ doping concentration effect on the temperature sensing properties of Er3+ containing materials is ignored. In this work, we demonstrated the influence of Er3+ concentration and excitation path on the spectral and temperature sensing properties in Er3+, Yb3+ co-doped NaGdTiO4 system. The NaGdTiO4: Er3+/Yb3+ phosphors were prepared by a high temperature solid state reaction method. Different spectral patterns for down- and up-conversion processes were observed and ascribed to the different excitation and population routes. The concentration quenching behaviors for down- and up-conversion processes were explained via cross relaxations between Er3+ ions. Most importantly, the Er3+ concentration dependent optical temperature sensing performance was observed and experimentally explained as a fact that the optical transition rate of Er3+ in different samples was changed with various Er3+ doping concentration. 相似文献
11.
12.
《Ceramics International》2016,42(5):5635-5641
A series of Yb3+ ions sensitized NaY(WO4)2:Er3+ phosphors were synthesized through a solid-sate reaction method. The X-ray diffraction (XRD), upconversion (UC) emission and cathodoluminescence (CL) measurments were applied to characterize the as-prepared samples. Under the excitation of 980 nm light, bright green UC emissions corresponding to (2H11/2,4S3/2)→4I15/2 transitions of Er3+ ions were observed and the UC emission intensities showed an upward trend with increasing the Yb3+ ion concentration, achieving its optimum value at 25 mol%. Furthermore, the temperature sensing behavior based on the thermally coupled levels (2H11/2,4S3/2) of Er3+ ions was analyzed by a fluorescence intensity ratio technique. It was found that the obtained samples can be operated in a wide temperature range of 133–773 K with a maximum sensitivity of approximately 0.0112 K−1 at 515 K. Ultimately, strong CL properties were observed in NaY(WO4)2:0.01Er3+/0.25Yb3+ phosphors and the CL emission intensity increased gradually with the increment of accelerating voltage and filament current. 相似文献
13.
Spectral management and energy‐transfer mechanism of Eu3+‐doped β‐NaGdF4:Yb3+,Er3+ microcrystals
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Lu Yao Dekang Xu Hao Lin Anming Li Shenghong Yang Yueli Zhang 《Journal of the American Ceramic Society》2017,100(10):4602-4610
β‐NaGdF4:Yb3+,Er3+ upconversion (UC) microcrystals were prepared by a facile hydrothermal process with the assistance of ethylene diamine tertraacetic acid (EDTA). The β‐NaGdF4 UC microcrystal morphology was controlled by changing the doses of EDTA and NaF. Uniform hexagonal structure can be obtained at the 2 mmol EDTA and 9‐10 mmol NaF. The UC emissions of β‐NaGdF4:Yb3+,Er3+ microcrystals were tuned by the variation of Eu3+ doping level (0%‐5%), where the red/green intensity ratio decreased with the Eu3+ concentration increase. It was found on the base of rate equations that with the Eu3+ doping, the energy back transfer process 2H11/2/4S3/2 (Er3+) → 4I13/2 (Er3+) decreased. In addition, an energy‐transfer process from 4F7/2 (Er3+) to 5D1 (Eu3+) and a cross relaxation process of 7H9/2 (Er3+) + 5D0 (Eu3+) → 4F7/2 (Er3+) + 5D2 (Eu3+) were proposed and verified by rate equations, which dominated the energy‐transfer mechanism between Er3+ and Eu3+, resulted in the spectra tuning of β‐NaGdF4:Yb3+,Er3+. The results suggested that the color tuning of β‐NaGdF4:Yb3+,Er3+,Eu3+ UC microcrystals would have potential applications in such fields as flat‐panel displays, solid‐state lasers, and photovoltaics. 相似文献
14.
Do-Hwan Kim Jeong Ho Ryu Jun Ho Chung Jong Won Eun Kwang Bo Shim Sung-Yong Cho 《Korean Journal of Chemical Engineering》2012,29(4):519-524
Er3+,Yb3+ co-doped CaWO4 polycrystalline powders were prepared by a solid-state reaction and their up-conversion (UC) luminescence properties were
investigated in detail. Under 980 nm laser excitation, CaWO4: Er3+,Yb3+ powder exhibited green UC emission peaks at 530 and 550 nm, which were due to the transitions of Er3+ (2H11/2)→Er3+ (4I15/2) and Er3+ (4S3/2)→Er3+ (4I15/2), respectively. Effects of Li+ tri-doping into CaWO4: Er3+,Yb3+ were investigated. The introduction of Li+ ions reduced the optimum calcinations temperature about 100 °C by a liquid-phase sintering process and the UC emission intensity
was remarkably enhanced by Li+ ions, which could be attributed to the lowering of the symmetry of the crystal field around Er3+ ions. 相似文献
15.
Emission from Mo‐O charge‐transfer state and Yb3+ emission in Eu3+‐doped and nondoped molybdates under UV excitation
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Molybdates of Li+ and Yb3+ are studied to investigate the luminescence under UV excitation. LiYb(MoO4)2 and Eu3+‐doped LiYb1‐xEux(MoO4)2 (x=001–1.0) phosphors were synthesized by solid state reaction under mixing of Eu2O3, Yb2O3, Li2CO3 and MoO2 in air atmosphere. Two broad absorption bands centered at 333 and 236 nm are observed in LiYb(MoO4)2 compound. They are attributed to the 1A1→1T1 and 1T2 transitions due to the O2?→Mo6+ electron transfers in MoO4 tetrahedron. An emission band with a peak at about 440 nm is found, which is attributed to the 3T1→1A1 transition of MoO4. Appearance of near‐infrared (NIR) Yb3+ emission observed under UV excitation is understood by the MoO4→Yb3+ Foerster‐Type energy transfer due to spectral overlap between the low‐energy tail of the broad 440 nm emission band and the high‐energy tail of the broad Yb3+ absorption band and due to short Yb3+‐MoO4 distance. Yb3+ emission observed in LiYb1?xEux(MoO4)2 by Eu3+ excitation is understood by the Eu3+→Yb3+ energy transfer by cross‐relaxation (CR) process between the 5D0→7F6 Eu3+ transition and the 2F7/2→2F5/2 Yb3+ transition. The CR efficiency shows maximum efficiency of 0.24 at x=0.15 of higher acceptor Yb3+ concentration than donor Eu3+ concentration. Three Yb3+ emission bands with peaks at 994, 1002, and 1023 nm are observed, depending on the excitation wavelength. This is explained by less‐shielded 4f electrons of Yb3+ by the 5s25p6 outermost electron shells, which are also responsible for unusual broadband Yb3+ absorption and emission. From appearance of NIR Yb3+ emission under excitation by not only UV light but also red light, these compounds are expected to be suitable for efficient photovoltaic application to Si‐based solar cells. 相似文献
16.
Highly Sensitive Optical Thermometry of Yb3+‐Er3+ Codoped AgLa(MoO4)2 Green Upconversion Phosphor
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Ting Li Chongfeng Guo Shaoshuai Zhou Changkui Duan Min Yin 《Journal of the American Ceramic Society》2015,98(9):2812-2816
Er3+–Yb3+ codoped AgLa(MoO4)2 phosphors with intense green emission from 2H11/2/4S3/2 → 4I15/2 transitions and negligible red emission from 4F9/2 → 4I15/2 transition of Er3+ were synthesized by sol–gel process. Its temperature sensing performance was evaluated based on the temperature dependence of fluorescence intensity ratio (FIR) of two green emission bands in the range 300–510 K. The maximum sensitivity of AgLa(MoO4)2: 0.02Er3+/0.4Yb3+ is approximately 0.018 K?1 at 480 K, which is much higher than those of reported samples based on green emissions of Er3+. Result suggests that AgLa(MoO4)2: Er3+/Yb3+ has a great potential application in optical temperature sensors. 相似文献
17.
Yanmin Yang Chao Mi Fuyun Jiao Xianyuan Su Xiaodong Li Linlin Liu Jiao Zhang Fang Yu Yanzhou Liu Yaohua Mai 《Journal of the American Ceramic Society》2014,97(6):1769-1775
Yb3+/Er3+ codoped La2S3 upconversion (UC) phosphors have been synthesized using high‐temperature solid‐state method. Under 971‐nm excitation, the maximum luminescence power can reach 0.64 mW at the excitation power density of 16 W/cm2 and an absolute power yield of 0.36% was determined by an absolute method at the excitation power density of 3 W/cm2, and the quantum yield of La2S3:Yb3+, Er3+ (green ~0.18%, red ~0.03%, integration ~0.21) was comparable to that of NaYF4:Yb3+, Er3+ nanocrystals (integration ~0.005–0.30). Frequency upconverted emissions from two thermally coupled excited states of Er3+ were recorded in the temperature range 100–900 K. The maximum sensitivity of temperature sensing is 0.0075 K?1. As the excitation power density increases, the temperature of host materials rapidly rises and the top temperature can reach to 600 K. Given the intense UC emission, high sensitivity, as well as good photothermal stability, La2S3:Yb3+/Er3+ phosphor can become a promising composite material for photothermal ablation of cancer cells possessing the functions of temperature sensing and in vivo imaging. 相似文献
18.
Effect of ligand field symmetry on upconversion luminescence in heat‐treated LaBGeO5:Yb3+, Er3+ glass
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Mohamed. A. Ali Jinjun Ren Xiaofeng Liu Jianrong Qiu 《Journal of the American Ceramic Society》2018,101(9):4387-4396
In this paper, we report upconversion (UC) luminescence enhancement in LaBGeO5:Yb3+, Er3+ glass‐ceramics (GCs), surface crystallized glass‐ceramics (SCGCs) and ceramics compared with the as‐melt glass fabricated by the conventional melt‐quenching technique. Based on structural investigations, we find that the nucleation and crystallization of trigonal stillwellite LaBGeO5:Yb3+, Er3+ nanocrystals occur first at the glass surface before the following volume crystallization. The local site symmetry around rare earth (RE) ions which was evaluated using the Eu3+ ions as a probe together with Judd‐Ofelt theory calculations exhibits a clear increase with the devitrification of the glass. Consequently, complete crystallization of the glass leads to largest enhancement in the UC emissions of the LaBGeO5:Yb3+, Er3+ ceramics. We ascribe the enhancement of UC luminescence in the LaBGeO5:Yb3+, Er3+ GCs, SCGCs, and ceramics to the structural ordering and the improvement of site symmetry surrounding RE ions that minimizes the rate of nonradiative relaxation process. 相似文献
19.
Microwave Sol–Gel Synthesis of CaGd2(MoO4)4:Er3+/Yb3+ Phosphors and Their Upconversion Photoluminescence Properties
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Chang Sung Lim Victor Atuchin Aleksandr Aleksandrovsky Maxim Molokeev Aleksandr Oreshonkov 《Journal of the American Ceramic Society》2015,98(10):3223-3230
CaGd2(MoO4)4:Er3+/Yb3+ phosphors with the doping concentrations of Er3+ and Yb3+ (x = Er3+ + Yb3+, Er3+ = 0.05, 0.1, 0.2, and Yb3+ = 0.2, 0.45) have been successfully synthesized by the microwave sol–gel method, and the crystal structure refinement and upconversion photoluminescence properties have been investigated. The synthesized particles, being formed after heat‐treatment at 900°C for 16 h, showed a well‐crystallized morphology. Under the excitation at 980 nm, CaGd2(MoO4)4:Er3+/Yb3+ particles exhibited strong 525 and 550‐nm emission bands in the green region and a weak 655‐nm emission band in the red region. The Raman spectrum of undoped CaGd2(MoO4)4 revealed about 15 narrow lines. The strongest band observed at 903 cm?1 was assigned to the ν1 symmetric stretching vibration of MoO4 tetrahedrons. The spectra of the samples doped with Er and Yb obtained under 514.5 nm excitation were dominated by Er3+ luminescence preventing the recording Raman spectra of these samples. Concentration quenching of the erbium luminescence at 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions in the CaGd2(MoO4)4:Er3+/Yb3+ crystal structure was established to be approximately at the 10 at.% doping level. 相似文献
20.
《Ceramics International》2017,43(16):13505-13515
ZnO-TiO2 composites co-doped with Er3+ and Yb3+ ions were successfully synthesized by powder-solution mixing method and their upconversion (UC) luminescence was evaluated. The effect of firing temperature, ZnO/TiO2 mixing ratio, and dopant concentration ranges on structural and UC luminescence properties was investigated. The crystal structure of the product was studied and calculated in detail by means of X-ray diffraction (XRD). Also, the site preference of Er3+ and Yb3+ ions in the host material was considered and analyzed based on XRD results and UC luminescence characteristics. Brightest UC luminescence was observed in the ZnO-TiO2:Er3+,Yb3+ phosphor fired at 1300 °C in which the system consisted of mixed phases; Zn2TiO4, TiO2, RE2Ti2O7 and RE2TiO5 (RE = Er3+ and/or Yb3+). Under the excitation of a 980 nm laser, the two emission bands were detected in the UC emission spectrum, weak green band centered at 544 and 559 nm, and strong red band centered at 657 and 675 nm wavelengths in accordance with 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ ion, respectively. The simple chemical formula equations, for explaining the site preference of Er3+ and Yb3+ ions in host crystal matrix, were generated by considering the Zn2TiO4 crystal structure, its crystal properties, and the effect of Er3+ and Yb3+ ions to the host crystal matrix. The UC emission intensity of the products was changed by varying ZnO/TiO2 mixing ratios, and Er3+ and Yb3+ concentrations. The best suitable condition for emitting the brightest UC emission was 1ZnO:1TiO2 doped with 3 mol% Er3+, 9 mol% Yb3+ fired at 1300 °C for 1 h. 相似文献