Zn~(2+)掺杂增强NaY(MoO_4)_2:Yb~(3+),Ho~(3+)荧光粉的上转换发光性能研究

采用高温固相法制备了一系列的NaY_(0.78-x)(MoO_4)_2∶0.2Yb~(3+),0.02Ho~(3+),xZn~(2+)(x=0,0.05,0.1,0.15,0.2,0.25)荧光粉。通过X射线衍射仪、扫描电镜以及荧光光谱仪分别对样品的结构、形貌和荧光性能进行了表征。结果表明Zn~(2+)的掺杂可以通过替换Y~(3+)格位和占据晶格间隙的方式进入基质晶格。在980nm激光激发下,样品呈现出了强烈的绿光(551nm)和相对微弱的红光发射(668nm),分别归因于Ho~(3+)的~5F_4,~5S_2→~5I_8和~5F_5→~5I_8跃迁。Zn~(2+)的掺杂可以使上转换发光强度显著增强,其原因是Zn~(2+)掺杂产生了O~(2-)空位而且可以裁剪Ho~(2+)周围的局域晶体场对称性。基于泵浦依赖的研究,对能级图和可能的上转换发光机理进行了详细的讨论。     

Er~(3+)/Yb~(3+)掺杂NaY(MoO_4)_2荧光粉的制备及其上转换发光性能研究

采用高温固相法合成了一系列Er~(3+)单掺和Er~(3+)/Yb~(3+)共掺NaY(MoO_4)_2荧光粉样品。通过X射线衍射仪、扫描电子显微镜、激光粒度仪和荧光光谱仪分别对样品的相纯度、微观形貌、粒径分布和上转换发光性能进行了表征。在980 nm激光激发下,Er~(3+)单掺和Er~(3+)/Yb~(3+)共掺样品的发射光谱中均能观测到中心波长位于536 nm、560 nm的上转换绿光发射和位于660 nm的红光发射,分别归因于Er~(3+)的~2H~(11/2)→~4I_(15/2)、~4S_(3/2)→~4I_(15/2)和~4F_(9/2)→4I_(15/2)能级跃迁。在Er~(3+)单掺体系中共掺Yb~(3+),可以轻松实现由上转换绿光到红光的转变。NaY_(1-x-y)(MoO_4)_2∶x Er~(3+),y Yb~(3+)样品中最优的Er~(3+)/Yb~(3+)掺杂浓度和最佳的烧结温度为x=0.04、y=0.5、T=850℃。基于泵浦依赖和能级图,在Er~(3+)单掺和Er~(3+)/Yb~(3+)共掺体系上转换发光过程中所涉及的能量转移机制被详细讨论。     

用于物品安全的Yb~(3+)单掺纳米颗粒的制备与表征

为了提高稀土荧光防伪系统的防伪力度,采用沉淀法制备了用于物品安全的Yb~(3+)单掺杂NaYF_4纳米颗粒。利用FT-IR分析了制备过程中间产物的化学组成。利用XRD和TEM对产物的形貌结构进行表征,并结合吸收光谱和发射光谱图,分析了不同掺杂浓度NaYF_4∶Yb~(3+)纳米颗粒发光特性。实验结果表明,Yb~(3+)与苯甲酸钠反应生成了多齿配合物,验证了苯甲酸钠在制备过程中起络合作用。在N_2氛围中经400℃煅烧4 h得到β-NaYF_4∶Yb~(3+)纳米颗粒,平均粒径为86 nm。该纳米颗粒在900 nm光的激发下具有930 nm～1080 nm的不可见红外发射(归属于Yb~(3+)的~2F_(7/2)→~2F_(5/2)),980 nm激发下具有475 nm的蓝色可见发射(归属于Yb~(3+)对的合作上转换发光),最大红外发射和蓝色上转换发射的样品掺杂浓度分别为5%和20%。研究结果表明NaYF_4∶Yb~(3+)纳米颗粒在物品追踪领域具有良好的应用前景。     

YP_5O_(14):Ho~(3+)、Er~(3+)、Tm~(3+)晶体的发光性质

本文用水热法合成了YP_5O_(14):Ho~(3+)、Er~(3+)、Tm~(3+)晶体,最大线度为49mm。测定了晶体的紫外可见吸收,激发和荧光光谱。观察到Ho~(3+)离子的~3K_7,Er~(3+)离子的~4G_(11/2)和Tm~(3+)离子的~1D_2能级有强的叠加吸收。用380nm激发,Ho~(3+)离子的~5S_2和Er~(3+)离子的~4S_(3/2)能级绿色荧光(550nm)发射较强,可望是一种绿色发光材料。值得注意的是引入Tm~(3+)离子会强化绿色发射。本文还讨论了Ho~(3+)—Er~(3+)离子间的敏化及Tm~(3+)→Ho~(3+),Er~(3+)离子的能量转移。     

Visible-light emission properties of α-TeO_2:Ho~(3+)/Yb~(3+)/Eu~(3+) nanoparticles via both up-and down-conversion modes

In this study,α-TeO_2:Ho~(3+)/Yb~(3+),α-TeO_2:Eu~(3+) and α-TeO_2:Ho~(3+)/Yb~(3+)/Eu~(3+) nanoparticles were prepared via a simple hydrothermal process.The up- and down-conversion properties of the as-prepared nanoparticles were tested at room temperature under a near-infrared photo source(980 nm) and UV-vis photo source,respectively.The results indicated that α-TeO_2 NPs were a kind of outstanding host material for both up- and down-conversion luminescence.The α-TeO_2:Ho~(3+)/Yb~(3+) nanoparticles showed sharp up-conversion emission at 545 and 660 nm under 980 nm excitation,ascribed to the ~5S_2→~5I_8 and ~5F_5→~5I_8(Ho~(3+)) transitions,and weaker down-conversion emission at 545 nm under 455 nm excitation,ascribed to the ~5S_2→~5I_8(Ro~(3+)) transitions.The α-TeO_2:Eu~(3+)nanoparticles showed strong down-conversion emission at 592 and 615 nm under 395 nm excitation,attributed to the ~5D_0→~7F_1 and~5D_0→~7F_2(Eu~(3+)) transitions.Possessing the advantages of these two luminescent materials,the as-prepared tri-doped samples ofα-TeO_2:0.5Ho~(3+)/10Yb~(3+)/3Eu~(3+)(mol.%) nanoparticles could successfully emit visible light via both up- and down-conversion modes.     

溶胶-凝胶法制备YAG:Ho~(3+),Yb~(3+)纳米晶

以稀土氧化物和硝酸铝为原料,采用溶胶-凝胶法合成了YAG:1%Ho~(3+),1%Yb~(3+)纳米晶,并通过正交试验法确定其干凝胶的合成条件.采用DTA-TG、XRD及TEM对干凝胶的合成过程、纳米晶的晶相组成及形貌进行了研究,表明干凝胶经1 200 ℃煅烧后形成了结晶完全的YAG相,无中间相产生.吸收光谱和上转换发射光谱分析表明,Yb~(3+)在材料的发光过程中具有传递能量的作用,Ho~(3+)在跃迁过程中发射出中心波长为650 nm的红色上转换荧光及540 nm的绿色上转换荧光.     

UC/DC luminescence of Ho~(3+) doped pyrochlore structured La_(2(1–x))Yb_(2x)TiO_5 phosphor synthesized by sol-gel method

Ho~(3+) doped La_(2(1–x))Yb_(2x)TiO_5 samples were prepared by sol-gel method. Pyrochlore structured powders were obtained under the annealing of the as-prepared samples at 1100 °C for 3 h in the air. All the samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM) and photoluminescent spectroscopy. When x=0, we obtained La_2TiO_5 phosphors. Monitored at 546 nm, the excitation spectrum of Ho~(3+) activated La_2TiO_5 phosphors consisted of a broad band originating from the charge-transfer band(CTB) between Ho~(3+) ions and the nearest neighboring O~(2–) ions at 250–280 nm and four sharp bands associated to f-f transitions of Ho~(3+) ions at 350–500 nm. Under the blue light excitation at 461 nm, Ho~(3+) ion in La_2TiO_5 emitted an intense green emission band at 546 nm due to the transition of ~5S_2, ~5F_4→~5I_8. Two intense bands were observed at 490 nm(blue, ~5F_3→I_8) and 663 nm(red, ~5F_5→~5I_8) in the up-conversion(UC) spectrum under 980 nm NIR laser excitation in La_2TiO_5 phosphors activated with Ho~(3+) alone, whereas they were much different from the down-conversion(DC) luminescent samples. When x=7.5 mol.%–17.5 mol.%, the UC emission spectra of them dominated at 546 nm(green, ~5S_2, ~5F_4→~5I_8) and enhanced significantly with the dose of Yb~(3+) ion. The decay curve also confirmed that the transitions of ~5F_4→~5I_8 and ~5S_2→~5I_8 were merged into one emission band at 546 nm.     

Yb~(3+)共掺杂Sr_2MgSi_2O_7∶Eu~(2+),Dy~(3+)长余辉发光材料的制备与性能研究

通过高温固相法制备了Sr_2MgSi_2O_7∶Eu~(2+),Dy~(3+),Yb~(3+)长余辉发光材料。采用XRD、SEM、激发光谱、发射光谱和余辉衰减曲线对Sr_2MgSi_2O_7∶Eu~(2+),Dy~(3+),Yb~(3+)长余辉发光材料的微观结构以及光学性能进行了表征,研究结果表明Sr_2MgSi_2O_7∶Eu~(2+),Dy~(3+),Yb~(3+)长余辉发光材料的晶体结构和显微结构均未发生明显变化。Yb~(3+)的引入使得Sr_2MgSi_2O_7∶Eu~(2+),Dy~(3+)显示出更优良的荧光性能和余辉性能,不同Yb~(3+)掺量对长余辉发光材料的陷阱深度和电子传输速率有显著影响。实验表明,当Yb~(3+)掺杂量为0.03时,Sr_2MgSi_2O_7∶Eu~(2+),Dy~(3+),Yb~(3+)的荧光光谱相对强度最强,且表现出最佳的余辉衰减性能。     

单基质白光荧光粉Gd_3PO_7∶Dy~(3+)的制备及其性能研究

采用湿化学法合成单基质的白光发射的Gd_3PO_7∶Dy~(3+)荧光粉,使用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FT-IR)、荧光光谱等对样品的物相结构、形貌与光学性能等进行表征。XRD检测结果表明所制备的样品为含有微量杂质相的Dy~(3+)掺杂单斜结构的Gd_3PO_7晶体。荧光光谱检测结果表明在276 nm属于Gd~(3+)的特征激发带激发下,发射出Dy~(3+)的特征黄色光发射带(~4F_(9/2)→~6H_(13/2))与蓝色光发射带(~4F_(9/2)→~6H_(15/2)),证实在Gd_3PO_7∶Dy~(3+)样品中出现了由Gd~(3+)到Dy~(3+)的能量传递现象。样品的发光强度随pH值和Dy~(3+)掺杂量的变化而变化,在pH值为6.00、Dy~(3+)掺杂量为0.5%的条件下制备的样品呈现相对更强的发光强度。Dy~(3+)掺杂量直接影响着Gd_3PO_7∶Dy~(3+)样品的发光颜色,当Dy~(3+)掺杂量为3%时所制备的Gd_3PO_7∶Dy~(3+)样品可发射出色坐标为(0.335,0.345)的白色光,这表明Gd_3PO_7∶Dy~(3+)是一种潜在的单基质白光发射荧光材料。     

Energy transfer and 2 μm emission in Tm~(3+)/Ho~(3+) co-doped(Y_(0.87)La_(0.1)Zr_(0.03))_2O_3 nanopowders

(Y_(0.87)La_(0.1)Zr_(0.03))_2O_3 nanopowders doped with various concentrations of Tm~(3+) and Ho~(3+) were prepared by the citrate method. The standard cubic Y_2O_3 phase can be matched in the Tm~(3+)/Ho~(3+) co-doped(Y_(0.87)La_(0.1)Zr_(0.03))_2 O_3 nanopowders. The nanopowders exhibit average particle sizes of 40,60, 80 and 100 nm after calcinated at 900,1000,1100 and 1200℃,respectively. The energy transfer from Tm~(3+) to Ho~(3+) and the optimum fluorescence emission around 2 μm were investigated. Results indicate that the emission bands at around 1.86 and 1.95 μm correspond to ~3 F_4→~3 H_6 transition of Tm~(3+) and ~5 I_7→~5 I_8 transition of Ho~(3+), respectively.Better spectral properties were achieved in Tm~(3+)/Ho~(3+) co-doped(Y_(0.87)La_(0.1)Zr_(0.03))_2O_3 nanopowders with the average size of 100 nm obtained at the conditions of the treatment of precursors calcinated at 1200 ℃ for 2 h doped with 1.5 mol% Tm~(3+) and 1 mol% Ho~(3+).     

Eu~(3+)/Sm~(3+)共掺K_2Gd(WO_4)(PO_4)荧光粉的发光性能及热稳定性研究

采用高温固相法制备了K_2Gd_(1-x-y)(PO_4)(WO_4):x Sm~(3+),y Eu~(3+)新型红色荧光材料,通过利用X射线衍射谱(XRD)、荧光光谱对其结构及发光性能进行了研究。结果表明,稀土离子S~(3+)的掺入没有改变荧光粉的晶相;样品的激发光谱在394 nm有很强的激发峰,与近紫外LED芯片匹配,且Eu~(3+)的~5D_0→~7F_2电偶极跃迁表现出616 nm有较好的红光发射,Eu~(3+)的最佳掺杂量(摩尔分数)为y=0.3;Sm~(3+)进入晶格后,激发峰明显增强和变宽,表明Sm~(3+)对Eu~(3+)的发光起到敏化作用;K_2Gd_(0.68)(PO_4)(WO_4)∶0.3Eu~(3+),0.02Sm~(3+)样品在150℃时发光强度仍为初始温度的78%,具有良好的热稳定性且色纯度高,是一种潜在的白光LED用荧光粉。     

Enhanced 1-5 μm near-and mid-infrared emission in Ho~(3+)/Yb~(3+)codoped TeO_2-ZnF_2 oxyfluorotellurite glasses

Intense 1-5 μm infrared emission from near-to mid-infrared was obtained from Ho~(3)+/Yb~(3+)codoped TeO_2-ZnF_2 oxyfluorotellurite glasses which were prepared by melt-quenching method under the 980 nm LD excitation,and the emission intensity can be enhanced with the increase of ZnF_2 content.Judd-Ofelt analysis was used to evaluate the radiative transition parameters of the excited levels according to the absorption spectra.The stimulated emission cross section of ~5 I6→~5 I_8(1.2 μm),~5 I7→~5 I_8(2.0μm),~5 I_6→~5 I_7(2.85 μm) and ~5 I_5→~5 I_6(4.0 μm) transitions were calculated to reach 0.639 × 10~(-20),0.760 ×10~(-20),0.985×10 20 and 0.484 × 10~(-20) cm~2,respectively.The energy transfer coefficients(C_(DA)) are enhanced with the increase of ZnF2 content and phonon contribution ratios of phonon assisted energy transfer process between Ho~(3+) and Yb~(3+)were figured out.Our results demonstrate that these TeO_2-ZnF_2 glasses,which possess good thermal stability and transparency,low phonon energy(about 600 cm~(-1)),excellent near-and mid-infrared emission in the range of 1-5 μm wavelength,would be promising material for infrared optical fibers and infrared lasers.     

级联激光在Tm~(3 )中的作用：YLF

在掺杂 Tm~(3 )的 LiYF_4中,由于级联激光的作用,在2.3μm 和1.88μm 观察到激励发射。5%Tm~(3 )。掺杂的单晶,用0.6943μm 红宝石激光沿纵向注入红宝石波长与 Tm 的(相当于~3H_6→~3F_3的)吸收跃迁是谐振的。从~3F_3到~3H_4能级的快速衰减,引起_3H_4和~3H_5之间的充填反转,产生2.3μm 的激光线。快速非幅射衰减到~3F_4能级,导致了相当于~3F_μ→~3H_5跃迁的1.88μm 激光作用。     

新型蓝色长余辉荧光粉SrAl_2O_(4-y)N_y∶Eu~(2+),Dy~(3+)发光性能研究

采用高温固相反应合成了SrAl_2O_(4-y)N_y∶Eu~(2+),Dy~(3+)系列长余辉荧光粉,并研究了SrAl_2O_(3.75)N_(0.25)∶Eu~(2+),Dy~(3+)体系的晶体结构、光谱特性、余辉衰减曲线及热释发光曲线。X射线衍射分析结果表明,SrAl_2O_(3.75)N_(0.25)∶Eu~(2+)荧光材料属六方晶系,P6322空间群,晶胞参数a=b=5.14,c=8.462,γ=120°。荧光光谱测试结果表明,SrAl_2O_(3.75)N_(0.25)∶Eu~(2+)的激发光谱和发射光谱均为宽带谱,激发光谱位于283 nm~450 nm,发射光谱的峰值位于487 nm,属于Eu~(2+)的4f65d1→4f7跃迁发射。Eu~(2+)的掺杂量并不改变SrAl_2O_(3.75)N_(0.25)∶Eu~(2+)发射光谱的形状和峰值位置,但对相对发光强度有较大影响,Eu~(2+)的摩尔浓度为2%时相对发光强度最高。余辉衰减曲线表明,Sr_(0.97)Al_2O_(3.75)N_(0.25)∶Eu_(0.02),Dy_(0.01)的余辉衰减符合指数衰减规律,由初始的快衰减和之后的慢衰减两个过程组成。通过热释发光曲线对荧光材料中的陷阱能级进行计算,得出Sr_(0.97)Al_2O_(3.75)N_(0.25)∶Eu_(0.02),Dy_(0.01)的能级陷阱为0.42 V,掺Dy~(3+)有利于提高该荧光材料的初始发光亮度和余辉时间。     

Li~+掺杂对Ca(W,Mo)O_4:Eu~(3+)红色荧光粉结构及发光性能的影响

采用高温固相反应法制备了一系列Li+掺杂的Ca(W,Mo)O_4∶Eu~(3+)荧光粉。通过X射线衍射仪、扫描电子显微镜及荧光光谱仪对样品的结构、形貌及荧光性能进行了表征。XRD及SEM结果表明,Li~+掺杂没有改变样品原有的四方晶系体心结构,Li+能够以替代和间隙掺杂的方式进入主晶格,适当的Li+掺杂可以改善样品的团聚现象。样品的激发光谱涵盖200~550nm的宽带激发,在395nm激发下,能发射出位于616nm处的窄带红光,归因于Eu~(3+)的~5D_0→~7F_2跃迁,适量Li~+的掺杂明显提升了样品的发光强度。与其他碱金属离子(Na~+、K~+)掺杂相比,Li~+由于半径最小、电负性最强,使得发光强度增强最多。     

M_2YSbO_6:RE~(3+)的合成、组成、结构及发光性能的研究(M=Ba、Ca;RE~(3+)=Sm、Dy、Ho、Er、Tm)

本文首次较系统地研究了稀土离子Sm~(3+)、Dy~(3+)、Ho~(3+),Er~(3+)、Tm~(3+)在具有不同结构的M_2YSbO_6(M=Ba、Ca)中的发光性能。合理地确定了各种谱项及跃迁。发现稀土离子的发光强烈地依赖于复合氧化物的晶体结构及其掺杂浓度。浓度猝灭是由于稀土激活离子对之间交叉驰豫无辐射跃迁所致。从实验上,确定了某些稀土离子发光的最佳浓度。结果表明Ca_2YSbO_6对Sm~(3+)、Dy~(3+)、Ho~(3+)、Er~(3+)是一个有效的基质并对激活离子具有敏化作用。发现重稀土激活离子Dy~(3+)黄光发射强度和兰光发射强度之比R随Dy~(3+)浓度的增加发生规律性的变化。并解释了其原因。     

WO_4~(2-)对红色荧光粉Na_2CaSiO_4∶Eu~(3+)发光性能的影响研究

研究采用高温固相法合成Eu~(3+),WO_4~(2-)共掺杂Na_2CaSiO_4系列红色荧光粉。通过X射线粉末衍射和荧光分析,研究荧光粉的结构和发光性能。考察了Eu~(3+),WO_4~(2-)掺杂量对荧光粉发光性能的影响。结果表明,掺杂了Eu~(3+),WO_4~(2-)后Na_2CaSiO_4仍为纯相,属立方晶系结构,但掺杂后晶胞参数发生变化,说明Eu~(3+),WO_4~(2-)已经进入晶格中。荧光粉发光强度随Eu~(3+),WO_4~(2-)掺杂含量的增加而增大。Eu~(3+)在晶体中的含量为20%时(以Na_2CaSiO_4物质的量为基准),荧光粉Na_2CaSiO_4∶Eu~(3+)的发光强度达到最大值。当WO_4~(2-)在晶体中的含量为0.07%时,此时,发射光的强度是掺杂前的2.74倍,色坐标为(0.66,0.34),更接近标准色坐标(0.67,0.33)。     

Intense single-band red upconversion emission in BiOCl:Er~(3+) layered semiconductor via co-doping Ho~(3+)

Exploring a new tuning way to facilely realize single-band red emission in trivalent rare-earth ions(RE~(3+)) doped upconversion(UC) materials is still desirable.In this work,the intense single-band red emission is achieved by co-doping only Ho~(3+)in the BiOCl:Er~(3+) under 1550 nm excitation.In the BiOCl layered host,co-doping Ho~(3+)can further enhance the red emission and simultaneously suppress the green emission of Er~(3+),and thus obviously improve the red-to-green(R/G) ratio.It is found that Ho~(3+)does not se rve as ene rgy trapping through the ~5 I_6 state as in traditional UC materials but acts as ET bridge(~4 S_(3/2),~2 H_(11/2)(Er~(3+))→~5 F_4,~5 S_2(Ho~(3+))→~4 F_(9/2)(Er3+)).The tuning mechanism of Ho3+is discussed in detail and further confirms through a comparative experiment.Our research gives an unusual perspective to tune the UC behavior of Er3+through co-doping Ho~(3+),which might be inspiring for achievement of single-band red UC emission.     

共沉淀法制备多孔纳米氟氧钇粉体及其性能研究

利用共沉淀法制备了具有稀土离子掺杂的氟氧钇(YOF∶Yb~(3+),Ho~(3+))多孔材料,并对其显微组织形貌、相结构、荧光性质、吸附能力以及表面润湿性进行了分析。结果表明,该纳米粉体颗粒具有尺寸小、均一性高的特点;其荧光发射能力随Ho~(3+)的增加逐渐降低,且荧光寿命较高;煅烧后多孔颗粒的表面积可达413.67m~2/g,其吸附性能及表面润湿性良好。     

Efficient near-infrared quantum cutting in Tb~(3+),Yb~(3+) codoped LuPO_4 phosphors

Tb~(3+) and Yb~(3+) codoped LuPO_4 phosphors were prepared by the reverse-strike co-precipitation method.The obtained LuPO_4:Tb~(3+),Yb~(3+) phosphors were characterized by X-ray diffraction(XRD),photoluminescence(PL) spectra and decay kinetics to understand the near-infrared quantum cutting(QC) phenomena.The XRD results showed that all the phosphors exhibited good crystallinity and had a pure tetragonal phase of LuPO_4.The experimental results showed that the strong green emission around 545 nm from Tb~(3+)(~5D_4→~7F_5) and near-infrared(NIR) emission at 1003 nm from Yb~(3+)(~2F_(5/2)→~2F_(7/2)) of LuPO_4:Tb~(3+),Yb~(3+)phosphors were observed under 489 nm excitation,respectively.The Yb~(3+) concentration dependence on luminescent properties and lifetimes of both the visible and NIR emissions were also investigated.The quenching concentration of Yb~(3+) ions approached as high as 10 mol.%.The excellent luminescence properties of the LuPO_4:Tb~(3+),Yb~(3+) indicated its potential application in improving the energy conversion efficiency of the silicon based solar cells by converting one blue photon to two NIR ones.