Er^(3+)共掺增强BaSi_(2)O_(2)N_(2)∶Eu^(2+)发光

针对Er^(3+)共掺增强BaSi_(2)O_(2)N_(2)∶Eu^(2+)发光效果的内在差异和可能机理进行了研究。通过XRD测试展示了共掺下的晶体结构,分析确认了样品纯度以及生长差异;为进一步研究差异的来源,监控了不同价态掺杂离子的发射光谱,对随Er^(3+)含量变化的发射光谱规律性变化进行展示,进而分析得出Er^(3+)共掺增强发光的内部物理机理是控制择优取向和对价态进行定向竞争调节;从发光体应用场景的温度范围需求进行了温度特性测试,展示了温度变化下的发射光谱变化。这项研究为调控发光强度、提高量子效率的工作提供了新的思路。

具有持续反应活性的g-C_(3)N_(4)/Sr_(2)MgSi_(2)O_(7):Eu^(2+),Dy^(3+)复合材料的光学-催化行为研究

为促进环境友好型光催化技术的应用推广,通过热解聚合方式将g-C3N4负载于多孔Sr_(2)MgSi_(2)O_(7):Eu^(2+),Dy^(3+)蓝色长余辉荧光粉上,制备具有持续反应活性的g-C_(3)N_(4)/Sr_(2)MgSi_(2)O_(7):Eu^(2+),Dy^(3+)复合材料。首次采用累积污染物降解效率等一系列指标评价材料在光照及暗态下综合去除污染物效果。通过微观表征手段和NO去除试验研究了单组分复配质量比对复合材料的光学及催化性能的影响。结果表明,g-C_(3)N_(4)的复合对Sr_(2)MgSi_(2)O_(7):Eu^(2+),Dy^(3+)的荧光强度和余辉性能产生了不利影响;但光照下,提高的光生载流子分离效率和光吸收能力使复合材料的光催化活性增强;暗态下,内在光源Sr_(2)MgSi_(2)O^(7):Eu^(2+),Dy^(3+)的存在赋予了复合材料持续去除NO的能力,该能力的持续时间与余辉亮度、光催化活性有关。本研究有助于推动持续活性光催化体系的发展。

Quenching Study on Iron Impurity in Eu^(2+), Dy^(3+) Doped Strontium Aluminate Phosphor Prepared by Nano-Coating Process

A series of long afterglow phosphors, Eu2+, Dy3+, with different iron content were prepared by nano-coating process. The resulted precursors were characterized by Transmission Electron Microscope (TEM), which suggested that the precursor particles had nanometer size distribution. The optical quenching of iron impurity on the phosphor powders were investigated by X-Ray powder Diffraction (XRD) and photoluminescence methods. The XRD indicates that a pure monoclinic SrAl2O4∶Eu2+, Dy3+ was formed at 1200 ℃ and iron impurity up to 296.36×10-4% had no effect on the SrAl2O4∶Eu2+, Dy3+ phase structure. However, the luminescence intensity were strongly dependent on the trace iron impurity, which might be explained that iron displace the aluminium and form Fe-O bond, which competed energy with Eu2+ and transfer red them to infrared sites.

Simultaneous enhancement of red luminescence and thermal stability of a novel red phosphor:A Li^(+)-Eu^(3+)co-occupied site strategy in BaAl_(2)Ge_(2)O_(8)lattices

The rapid development of phosphor-converted white light emitting diodes(pc-WLEDs)requires new red phosphors with efficient and thermally stable luminescence for high-quality warm-white lighting.However,it is still a challenge to discover red phosphors with facile synthesis,high internal quantum efficiency(IQE),excellent thermal stability and high color purity.Herein,a novel red-emitting Eu^(3+)activated barium dialuminum digermanate(BaAl_(2)Ge_(3)O_(8),EAGO)phosphor showing strong red emission at 610 nm was prepared.The IQE is improved from 32.91%to 78.84%by employing a charge compensation strategy.The lithium-ion co-dop ed BAGO:Eu^(3+)phosphor exhibits a nearly twofold increase in integral photoluminescence(PL)intensity and the high color purity reaches 94.17%.Impressively,the PL intensity of the BAGO:Eu^(3+),Li^(+)phosphor drops by only 2.6%at 150℃of that at room temperature.Finally,the pc-WLED using the red BAGO:Eu^(3+),Li^(+)phosphor exhibits white light with the chromaticity coordinate of(0.3515,0.3495),a high color-rendering index of 92 and a low correlated color temperature of 4746 K.All these results manifest that BAGO:Eu^(3+),Li^(+)phosphor is a suitable red phosphor for nearultraviolet(NUV)chip-based pc-WLEDs.

A comparison research on replacements of Ba^(2+)by Lu^(3+)and Ba^(2+)-Si^(4+)by Lu^(3+)-Al^(3+)in BaSi_(2)O_(2)N_(2):Eu phosphors

As a cyan-emitting oxonitridosilicate phosphor,BaSi_(2)O_(2)N_(2):Eu^(2+)can be used as a competent cyan compensator to improve the color rendering index of white light-emitting diodes(WLEDs).However,low luminescence efficiency and poor thermal stability of this type of phosphor seriously suppress its actual application in full-spectrum lighting.The replacements of Ba^(2+)by Lu^(3+)and Ba^(2+)-Si^(4+)by Lu^(3+)-Al^(3+)can greatly increase the luminescence intensity and improve the thermal stability at the same time.With Lu^(3+)doping,the internal quantum efficiencyηIQE Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+)is 24.08%higher than that of Ba_(0.97)Si_(2)O_(2)N_(2):0.03 Eu^(2+).After Al^(3+)co-doping,theηIQE is further increased by 10.31%compared to Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+).When the temperature rises to 473 K,the luminescence intensity of Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+)maintains 62.32%of that at room temperature,which increases by 17.35%in relative to the Ba_(0.97)Si_(2)O_(2)N_(2):0.03 Eu^(2+),while the luminescence intensity of Ba_(0.925)Si_(1.97)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+),0.03 Al^(3+)keeps 73.87%of the initial value,which increases by18.52%compared to Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+).The mechanisms for luminescence and thermal stability improvement are proposed.The Ba_(0.925)Si_(1.97)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+),0.03 Al^(3+)cyan phosphor,Y3 Al5 O12:Ce3+yellow phosphor and CaAlSiN3:Eu^(2+)red phosphor are mixed thoroughly and coated on a blue LED(450 nm)to assemble a WLED.The WLED demonstrates a color rendering index(Ra)of 97.1 at150 mA,and the R1-R15 values are all above 90.The results indicate that as an effective cyan compensator in WLED,the BaSi_(2)O_(2)N_(2):Eu^(2+),Lu^(3+),Al^(3+)phosphor has great application prospect in the field of full-spectrum lighting.

Emission tunable of Mg_(0.695)Si_(0.695)Al_(1.39)O_(3.65)N_(0.35):Eu^(2+),Mn^(2+) oxynitride phosphors via energy transfer for WLEDs

A series of Eu^(2+)doped and Eu^(2+)/Mn^(2+) co-doped Mg_(0.695)Si_(0.695)Al_(1.39)O_(3.65)N_(0.35)(MSAON) phosphors were synthesized by solid-state reaction at a lower temperature of 1500℃.The crystal morphology and structure of MSAON host were characterized by SEM,TEM and XRD.The quantum yield(QY) for Eu^(2+)doped MSAON phosphors was measured as high as 62%,indicating the excellent luminous efficiency.For the Eu^(2+)/Mn^(2+)co-doped MSAON phosphor,the photoluminescence spectrum and delay curves reveal the efficient energy transfer(ET) process from Eu^(2+)to Mn^(2+)ions.Meanwhile,the corresponding energy transfer efficiency,critical distance and mechanism are discussed in detail.Temperature-dependent emission spectrum shows the thermal and color stabilities.The emission color of MSAON:Eu^(2+),Mn^(2+)phosphors could be tuned from blue through white to red via varying the concentration of Mn^(2+) ions.White-light-emitting diodes(WLEDs) were successfully fabricated by encapsulating the phosphors in nUV LED(365 nm) devices obtaining white light with color rendering index(CRI) as high as 87.7.The results reveal that the MSAON:Eu^(2+),Mn^(2+)phosphors could have potential application in the field of n-UV WLEDs.

Eu^(2+),Dy^(3+)(Gd^(3+))共掺杂CaSi_2N_2O_2荧光粉发光性质

在还原气氛下采用高温固相法合成了白光发光二极管(LED)用荧光粉Ca_(0.98-y)Si_2N_2O_2:0.02Eu^(2+),yM^(3+),其中M为Gd(1%～12%)或者Dy(0.25%～6%)。利用X射线衍射仪分析其物相结构,发现稀土离子的掺入并没有改变其主晶相,仍为单斜结构。利用荧光分光光度计测试并分析激发光谱与发射光谱,样品在380 nm处有很宽的激发谱带,在位于550 nm处存在很宽的发射谱带,此发射谱归因于Eu^(2+)离子5d-4f的电子跃迁。Dy^(3+)与Gd^(3+)离子对Eu^(2+)发光具有明显的敏化作用:Dy^(3+)的摩尔分数为1%时,发光强度增加39%,达到最大值;Gd^(3+)则在摩尔分数为6%时,发光强度最强,增强了43%。并根据掺杂离子的能级特点对其发光微观机制进行了初步探讨。

Fine-grained phosphors for red-emitting mini-LEDs with high efficiency and super-luminance

Mini-LED backlights,combining color conversion materials with blue mini-LED chips,promise traditional liquid crystal displays(LCDs)with higher luminance,better contrast,and a wider color gamut.However,as color conversion materials,quantum dots(QDs)are toxic and unstable,whereas commercially available inorganic phosphors are too big in size to combine with small mini-LED chips and also have strong size-dependence of quantum efficiency(QE)and reliability.In this work,we prepare fine-grained Sr_(2)Si_(5)N_(8):Eu^(2+)-based red phosphors with high efficiency and stability by treating commercially available phosphors with ball milling,centrifuging,and acid washing.The particle size of phosphors can be easily controlled by milling speed,and the phosphors with a size varying from 3.5 to 0.7 mm are thus obtained.The samples remain the same QE as the original ones(~80%)even when their particle size is reduced to 3.2-3.5 mm,because they contain fewer surface suspension bond defects.More importantly,SrBaSi_(5)N_(8):Eu^(2+)phosphors show a size-independent thermal quenching behavior and a zero thermal degradation.We demonstrate that red-emitting mini-LEDs can be fabricated by combining the SrBaSi_(5)N_(8):Eu^(2+)red phosphor(3.5 mm in size)with blue mini-LED chips,which show a high external quantum efficiency(EQE)of above 31%and a super-high luminance of 34.3 Mnits.It indicates that fine and high efficiency phosphors can be obtained by the proposed method in this work,and they have great potentials for use in mini-LED displays.