Luminescent properties of Ca2SiO4:Eu3+ red phosphor for trichromatic white light emitting diodes

The luminescent properties of Eu3 doped Ca2SiO4 red phosphors synthesized by the flux fusion reaction method were investigated. It was found that the excitation spectrum included two regions: the weak excitation band below 325 nm and strong narrow peaks above 325 nm. The main peak of the excitation band was located at 400 nm. The peaks located at 290 nm were assigned to the combination of the charge transfer transition of O-Eu, peaks above 325 nm (325, 385, 400, 470, 511, and 539 nm) were assigned to the f–f transitions of Eu3 . The emission spectrum was dominated by the red peak located at 612 nm due to the electric dipole transition of 5D0–7F2. In addition, the ef- fects of the Eu3 content and charge compensators of Li , Na , K , and Cl– ions on the emission intensity were investigated. The experiment results suggested that the strongest emission was obtained when the concentration of the Eu3 ions was 0.3 mol–1, and Li ions gave the best improvement to enhance the emission intensity. Ca2SiO4:Eu3 , Li was thus suitable for low-cost trichromatic white light emitting diodes (WLED) based on UV InGaN chip.     

溶胶-凝胶法制备Ca3Al2O6：Eu3+红色荧光粉及其发光性能

采用溶胶-凝胶法合成Ca3Al2O6：Eu3+红色荧光粉,通过XRD、SEM、荧光光谱分别对样品的结构、形貌以及发光性能进行表征,讨论煅烧温度、Eu3+掺杂浓度以及电荷补偿剂对样品发光性能的影响.结果表明：实验所得样品的结构与Ca3Al2O6相同,Eu3+掺杂并没有改变其晶体结构.合成的荧光粉在394 nm近紫外光激发下发出615 nm明亮的红光.样品的红光强度随着煅烧温度的升高先增加后减弱,最佳烧结温度为1200℃.同样红光强度也随着Eu3+掺杂浓度的增加先增加后减弱,最佳Eu3+掺杂浓度为4%（摩尔分数）.加入电荷补偿剂后样品的发光强度均增强,其中加入K+后发光增强的效果最显著.该铝酸盐红色荧光粉性质稳定,在白光LED近紫外芯片激发中具有潜在的应用.     

Photoluminescence properties of a blue-emitting phosphor Eu2+-activated Ca3ZnAl4O10

A new aluminate host material Ca3ZnAl4O10 doped with Eu2+ was prepared by a high-temperature solid-state reaction method, and a pure crystalline phase of Ca3ZnAl4O10 was confirmed with X-ray powder diffraction (XRD) measurement. The luminescent property was investigated with excitation and emission spectra. The phosphor could be excited by UV light from 220 nm to 400 nm and emitted a blue luminescence peaked at 450 nm, which corresponded to the 4f65d1→4f7 transition of Eu2+ ions. The dependence of luminesce...     

A NIR to NIR rechargeable long persistent luminescence phosphor Ca2Ga2GeO7:Yb3+,Tb3+

Near infrared to near infrared (NIR–NIR) photo-stimulated persistent luminescence (PSPL) has shown excellent potential in high-resolution bioimaging for deep tissues. However, the PSPL in NIR-Ⅱ region (900–1700 nm) is still lacking. In this work, Ca₂Ga₂GeO₇:Yb³⁺,Tb³⁺ (CGGYT) phosphor with unique low-dimensional crystal structure was synthesized by high-temperature solid–state reaction. Thanks to the carriers transferring from deep traps to shallow ones induced by low energy light, the 978 nm PSPL originating from ²F_5/2 to ²F_7/2 transition of Yb³⁺ induced by multimode stimulating (980 nm or WLED) is successfully realized after pre-excited by UV lamp. The NIR PSPL of the specimen can be repeatedly stimulated after placed in dark for 12 h. Moreover, the results indicate that codoping with Tb³⁺ can significantly enhance the NIR-II PSPL owing to the quantum cutting persistent energy transfer (QC PET) from Tb³⁺ to Yb³⁺. Our study points to a new direction for the future development of multimode PSPL materials for bioimaging or multimode optical storage applications.     

A new oxyapatite red phosphor Eu3+-doped Ca3Y7(BO4)(SiO4)5O: Synthesis,structure and luminescence properties

A series of new oxyapatite red phosphors Ca₃Y₇(BO₄)(SiO₄)₅O doped with different concentrations of Eu³⁺ were successfully synthesized by high temperature solid state method. The X-ray diffraction (XRD) Rietveld refinement results show that the structure of the phosphor belongs to space group P6₃/m and Eu³⁺ ion replaces Y³⁺ ion. The emission spectrum consists of the characteristic emission peaks corresponding to Eu³⁺ under the excitation of 274 nm and the dominant emission peak is at 614 nm (⁵D₀→⁷F₂ of Eu³⁺). The concentration quenching effect occurs and the optimized Eu³⁺ concentration is 4.0 mol%. The energy level diagram for luminous mechanism is also given and the non-radiative energy transfer mechanism between Eu³⁺ is mainly exchange interaction. The CIE coordinate is close to the ideal red light and the color purity is higher than 99.79%. Moreover, the phosphor exhibits moderate thermal stability because the photoluminescence intensity at 423 K is still maintained at higher than 78.97% of that at room temperature. The internal quantum efficiency of Ca₃Y₇(BO₄)(SiO₄)₅O:4.0 mol%Eu³⁺ phosphor is 58.2%. A red light emitting diode (LED) device based on it can emit bright red light. The CCT values of the device are basically unchanged when driven by various bias current. The results show that Ca₃Y₇(BO₄)(SiO₄)₅O:Eu³⁺ is a new type of oxyapatite red fluorescent material with good comprehensive performances.     

Intense blue-emitting Ca2PO4Cl:Eu2+ phosphor for near-ultraviolet converting white light-emitting diodes

A blue phosphor Ca₂PO₄Cl:Eu²⁺ (CAP:Eu²⁺) was synthesized by solid state reaction. The Ca₂PO₄Cl:Eu²⁺ exhibited high quantum efficiency and excellent thermal stability. The luminescent intensity of Ca₂PO₄Cl:Eu²⁺ was found to be 128% under excitation at 380 nm, 149% under 400 nm, and 247% under 420 nm as high as that of BaMgAl₁₀O₁₇:Eu²⁺. The optimal doping concentration was observed to 11 mol.% of CAP:Eu²⁺. The energy transfer between Eu²⁺ ions in CAP were occurred via electric multipolar interaction, and the critical transfer distance was estimated to be 1.26 nm. A mixture of blue-emitting Ca₂PO₄Cl:Eu²⁺, green-emitting (Ba,Sr)₂SiO₄:Eu²⁺ and red-emitting CaAlSiN₃:Eu²⁺ phosphors were selected in conjunction with 400 nm chip to fabricate white LED devices. The average color-rendering index R_a and correlated color temperature (T_c) of the white LEDs were found to be 93.4 and 4590 K, respectively. The results indicated that it was a promising candidate as a blue-emitting phosphor for the near-UV white light-emitting diodes.     

Combustion synthesis and luminescence properties of Ca4Y6(SiO4)6O:Eu3+red phosphor for white LEDs

Eu3+activated Ca4Y6(SiO4)6O phosphors were prepared by combustion synthesis method, and their morphologies and lu-minescent properties were investigated. Field scanning electron microscopy (FSEM) confi...     

Moisture-induced degradation of the narrow-band red-emitting SrLiAl3N4:Eu2+ phosphor

The degradation of materials plays an important role in their application and service process. In this work, the moisture-induced degradation of SrLiAl₃N₄:Eu²⁺ (SLAN), a very promising narrow-band red-emitting phosphor, was comprehensively investigated by treating it in two different moisture conditions in order to reveal the potential mechanism and optimize the luminescence properties. The degradation rate gradually slows down with the decreasing environmental humidity indicating that water plays a key role in the degradation. Moreover, we take the other option with 100% humidity at different temperatures for rapid degradation. In the rapid degradation, the luminescence of SLAN is quenched quickly and the phase and microstructure change obviously, with the phosphor being bleached. The host turns into NH₃, Al₂O₃, Sr₃Al₂(OH)₁₂ and LiAl₂(OH)₇ finally. It is further confirmed that the rapid degradation occurs with the help of water and the phosphor is oxidized during this process.     

A single-phase full-color phosphor Sr2Ca2La(PO4)3O:Eu2+,Tb3+,Mn2+: Photoluminescence and energy transfer

A single-phase full-color emitting phosphor Sr₂Ca₂La(PO₄)₃O:Eu²⁺,Tb³⁺,Mn²⁺ was synthesized by the high temperature solid-state method. The phase formation, luminescence properties, thermal stability, and energy transfer from Eu²⁺ to Tb³⁺ and Eu²⁺ to Mn²⁺ in Sr₂Ca₂La(PO₄)₃O were investigated in details. Tunable emission color from blue to blueish green or orange can be observed under 365 nm near-ultraviolet excitation based on the energy transfer from Eu²⁺ to Tb³⁺ or Mn²⁺ ions by varying the ratio of Eu²⁺/Tb³⁺ or Eu²⁺/Mn²⁺ ions. White light was obtained with chromaticity coordinates of (0.3558, 0.3500) in the Sr₂Ca₂La(PO₄)₃O:0.04Eu²⁺,0.08Tb³⁺,0.40Mn²⁺ phosphor, suggesting their potential applications in white light emitting diodes.     

A novel long lasting phosphor Sr5 (PO4)3FxCl1-x:Eu2+,Gd3+prepared in air condition

A series of blue long afterglow mixed halide-phosphate phosphors Sr5 (PO4)3 FxCl1-x:Eu2+,Gd3+were synthesized in air by traditional solid-state reaction route. The crystal structures, photoluminescence...     

A potential single-phased white-emitting LiBaBO3:Ce3+,Eu2+ phosphor for white LEDs

Ce3+/Eu2+ co-doped LiBaBO3 phosphor was synthesized by high temperature solid-state reaction method, and its luminescent character- istics were investigated. The hues of the LiBaBO3:Ce3+, Eu2+ phosphor varies from blue to white and eventually to yellow-green by properly tuning the Ce3+/Eu2+ ratio. Under UV excitation, white light was generated by coupling blue and yellow-green emission bands attributed to Ce3+ and Eu2+ emissions, respectively. The luminous efficacy of LiBaBO3:1%Ce3+, 2%Eu2+ calculated from ...     

Effect of Eu3+ doping on luminescence properties of a KAlSiO4:Sm3+ phosphor

This study presents the photoluminescence characteristic analysis of a series of red phosphors of KAlSiO₄:1.5 mol%Sm³⁺,x mol%Eu³⁺ (x = 2, 3, 4, 5, 6, 7) prepared via high-temperature solid-phase reaction. The results show that the X-ray diffraction (XRD) refinement results are reliable. The unit cell parameters and volume gradually decrease as the Eu³⁺ concentration increases, resulting in a grain size reduction of 10.22%. When x = 6, the emission peaks of Sm³⁺ at 564, 601, and 651 nm disappear completely, and the corresponding full width at half maximum becomes 0. At 610 nm, the emission peak intensity of Eu³⁺ is increased by a factor of 4.8. The resonant non-radiative energy transfer effect is greater than the co-excitation effect. A maximum energy transfer efficiency of 97.8% is achieved. The integral area at 610 nm is as high as 85%. The color purity of the phosphor is as high as 92.97%, and the internal quantum yield gradually changes from 32% to 51%. Ultimately, these results confirm that the silicate phosphor is suitable for the red component in the three primary color phosphors of white light-emitting diodes.     

Tunable luminescence of Ce3+/Li+,Eu2+ co-doped Ca4(PO4)2O phosphor for white light emitting diodes

Phosphors Ca4(PO4)2O:Ce3+/Li+,Eu2+ were prepared by solid state reaction successfully, and characterized by X-ray diffraction, UV-Vis spectrometer and photoluminescence spectrometry. The as-prepared phosphors exhibited strong absorption in the UV-visible region and dual-emission bands centered at approximately 460 and 630 nm. Energy transfer from Ce3+ to Eu2+ was also observed. By varying the excitation wavelength, these new phosphors exhibited tunable emissions from blue to white and then to yellow, making them potential candidates as UV-convertible phosphors for white light emitting diodes.     

Eu3+-doped BaLiZn3(BO3)3: A novel red-emitting phosphor for blue chips excited white LEDs

A series of novel red-emitting BaLiZn₃(BO₃)₃:Eu³⁺ phosphors were synthesized through the high temperature solid state reaction method. The phase composition, crystal structure, morphology and photoluminescence property of the BaLiZn₃(BO₃)₃:Eu³⁺ samples were systematically investigated. The phosphor can be efficiently excited by the near ultraviolet light (NUV) of 396 nm and blue light of 466 nm, and give out red light emission at 618 nm corresponding to the electric dipole transition (⁵D₀→⁷F₂). The optimal doping concentration of Eu³⁺ ions in BaLiZn₃(BO₃)₃ is determined to be about 3 mol%, and the concentration-quenching phenomenon arise from the electric dipole–dipole interaction. The temperature dependent luminescence behavior of BaLiZn₃(BO₃)₃:0.03Eu³⁺ phosphor exhibits its good thermal stability, and the activation energy for thermal quenching characteristics is calculated to be 0.1844 eV. The decay lifetime of the BaLiZn₃(BO₃)₃:0.03Eu³⁺ is measured to be 1.88 ms. These results suggest that the BaLiZn₃(BO₃)₃:Eu³⁺ phosphors have the potential application as a red component in white light emitting diodes (WLEDs) with NUV or blue chips.     

Vacuum ultraviolet excited photoluminescence properties of Gd2O2CO3:Eu3+ phosphor

The Gd2O2CO3:Eu3 with type-II structure phosphor was successfully synthesized via flux method at 400℃ and their photoluminescence properties in vacuum ultraviolet (VUV) region were examined. The broad and strong excitation bands in the range of 153-205 nm owing to the CO32- host absorption and charge transfer (CT) of Gd3 -O2- were observed for Gd2O2CO3:Eu3 . Under 172 nm excitation, Gd2O2CO3:Eu3 exhibited strong red emission with good color purity, indicating Eu3 ions located at low symmetry sites and the chromaticity coordination of luminescence for Gd2O2CO3:Eu3 was (x=0.652, y=0.345). The photoluminescence quenching concentration of Eu3 excited by 172 nm for Gd2O2CO3:Eu3 was about 5%. Gd2O2CO3:Eu3 would be a potential VUV-excited red phosphor applied in mercury-free fluorescent lamps.     

New red phosphor （Y, Gd, Lu）BO3： Eu^3＋ for PDP applications

Highly efficient phosphors under vacuum ultraviolet excitation are still demanded for the development of plasma display panels and Hg-free fluorescent lamps. The phosphors of Eu3+ doped (Y, Gd, Lu)BO3 were synthesized with solid state reaction method and the con-tents of Y3+, Gd3+, and Lu3+ for plasma display panel red phosphor were optimized under vacuum ultraviolet excitation. Two new potential candidates, which were (Y1-S-7TGdSLuT)BO3: Eu3+ (0相似文献   

A green-yellow emitting β-Sr2SiO4:Eu2+ phosphor for near ultraviolet chip white-light-emitting diode

Sr2SiO4:xEu2 phosphors were synthesized through the solid-state reaction technique. The crystal phase of Sr2SiO4:xEu2 phosphor manipulated by Eu2 concentration was studied. The phase transited from β to α′ in Sr2SiO4:xEu2 phosphor with increasing europium concentration. The single β phase was formed as x≤0.005 and changed α′ phase when x>0.01. The emission spectrum of the β-Sr2SiO4:Eu2 phosphor consisted of a green-yellow broadband peaking at around 540 nm and a blue band at 470 nm under near ultraviolet excitation. The white LEDs by combining near ultraviolet chips with β-Sr2SiO4:Eu2 phosphors were fabricated. The luminous efficiency (15.7 lm/W) was higher than α′-Sr2SiO4:Eu2 phosphor white LED.     

Synthesis and photoluminescence properties of novel red-emitting Ca14Mg2(SiO4)8:Eu3+/Sm3+ phosphors

Novel red-emitting Eu3+, Sm3+ singly doped and co-doped Ca14Mg2(SiO4)8 phosphors were prepared by conventional solid- state reaction. Powder X-ray diffraction patterns were employed to confirm phase pu...     

A novel white-emitting phosphor ZnWO4:Dy3+

A new white luminescent material Dy3+ doped Zn WO4 was synthesized by hydrothermal route followed by calcining process. The phase structure, morphology and luminescent properties of as-synthesized samples were characterized by X-ray diffraction, scanning electron microscopy and fluorescence spectrophotometry, respectively. The results indicated that the sample was pure Zn WO4:Dy3+ only when the p H value of the reaction system was 6. The Zn WO4:Dy3+ sample was composed of spherical particles, and the particle size was about 80–130 nm. The excitation spectrum consisted of a broad band ascribed to the charge transfer transition from oxygen ligand to tungsten ion. The emission spectrum of Zn WO4:Dy3+ was composed of two major parts: the broad band attributing to the intrinsic emission of WO42– and the 4F9/2→6H15/2 transition of Dy3+, and the sharp emission peak corresponding to the 4F9/2→6H13/2 transition of Dy3+. The optimal emission intensity of the Zn1–xWO4:Dy3+x phosphors was realized when x=1.5 mol.%. Moreover, all of the Zn1–xWO4:Dy3+x(x=0.5 mol.%, 1 mol.%, 1.5 mol.%, 2 mol.%) phosphors could exhibit white light emission, which could be potentially applied in white lighting-emitting diodes.