Ba2+,Al3+,Sr2+掺杂YF3∶Ho3+,Yb3+上转换发光的研究

为了提高上转换材料在激光防伪领域的绿光发射强度,采用高温固相法制备Ba2、Al3+、Sr2+掺杂YF3∶Ho3+,Yb3+材料.通过980 nm近红外激发的上转换发射光谱,可知Ba2+、Al3+、Sr2+的掺杂都会使得晶格收缩,降低稀土离子周围晶体场的对称性,其546 nm绿光强度分别是未掺杂该金属离子样品的1.6倍、1.1倍、1.2倍.并根据X射线衍射(XRD)探究Ba2+含量对晶相的作用.通过差热分析(DTA)、上转换发射光谱、XRD、扫描电子显微镜(SEM),结果表明:对于最佳Ba2、Al3+、Sr2+掺杂含量但不同烧结温度的样品,当合成温度为940℃时发光性能、结晶度和晶粒生长较好.通过发射强度与激发电流的拟合结果,说明546 nm绿光是双光子吸收过程,并阐述980 nm激发YF3∶Ho3+,Yb3发光材料的能级跃迁过程.     

(Y0.99-xCe0.01Gdx)3Al5O12-Al2O3共晶的生长和性能研究

采用光学浮区法生长了质量较好(Y0.99-xCe0.01Gdx)3Al5O12-Al2O3共晶,直径约为7 mm,长度约为25 mm.通过XRD分析,结果表明共晶中只有Al2O3和YAG两种晶相;通过SEM观察表明,两种晶相在三维空间交错生长,形成自生互穿网络结构,共晶间距为10 μm左右.在室温下,进行了发射光谱和荧光寿命的测试,发现随着Gd3+浓度的增加,发射光谱发生了红移,最大发射波长从555 nm移至570 nm,荧光寿命为65 ns附近,并测试了共晶荧光体与大功率蓝光芯片匹配所得的光色性能.     

Ce3+敏化YAG∶Nd3+单晶的近红外发光性能研究

稀土离子的近红外发光性能在光通信和太阳能利用等领域应用广泛.针对材料近红外发光性能较弱的问题,采用Ce3的敏化作用,提高Nd3+的近红外发光性能.利用提拉法生长得到大尺寸的Ce3和Nd3+共掺杂Y3Al5O12(YAG)单晶,用X-射线衍射仪对其物相进行分析,并通过透射光谱对晶体透光率和吸收性质进行了表征.通过对Ce3+的激发和发射光谱分析,初步判断Ce3+和Nd3+间的能量传递行为.并通过Nd3+近红外激发和发射光谱分析,研究Ce3+对Nd3+发光的影响.实验结果表明,由于Ce3向Nd3+的有效能量传递作用,YAG∶Ce3+,Nd3+在450 nm蓝光激发时,近红外1 060 nm发光增强1.5倍.     

Cr2O3含量对YAl1-xCrxO3红色料物相组成与显微结构的影响

采用XRD、FESEM及EDS等多种分析方法,研究了Cr2O3含量对铬钇铝红(YAl1-xCrxO3)色料物相组成和显微结构的影响,探讨了Cr3+取代部分Al3+离子后,色料主晶相(YAlO3)、次晶相(Al2Y4O9)、残余相的变化及显微结构的不同.结果表明:随着Cr2O3含量的增加,合成色料颗粒由圆粒状长成典型的钙钛矿型立方形晶体和由于畸变形成的类四方形晶体;立方和类四方形颗粒为主晶相,圆粒状颗粒中Y2O3含量比主晶相中的高;由于立方型向正方型的晶格畸变,晶胞参数有所改变;当x为0.05～0.13时,色料有最好的红度值,此时主晶相晶形完整,大小均匀,发育良好.     

Co2+,Er3+:Y3Al5O12晶体的生长及其吸收特性

应用中频感应提拉法成功生长出新型的Co2+,Er3+:Y3Al5O12晶体.研究了室温下晶体的吸收光谱性能.结合Er3+:Y3Al5O12晶体的光谱,并利用调Q判据对Co2+,Er3+:Y3Al5O12晶体调Q特性进行了简单的分析.结果表明Co2+,Er3+:YAG晶体是一种很有潜力的自调Q激光晶体.     

溶液中杂质离子对石膏晶须生长的影响

为查明以工业石膏为原料制备石膏晶须时溶解的杂质离子对晶须的影响,在分析典型工业石膏主要杂质离子的基础上,对溶液中含有Na+、Al3+、K+、Sr2+、Mg2+和F-杂质离子时石膏晶须的制备进行了研究.采用XRD、IR 光谱、光学显微镜和ICP-AES对石膏晶须样品进行了表征,讨论了杂质离子对石膏晶须物相、结构、化学组成和形貌的影响.结果表明,碱金属离子Na+、K+及高电荷惰性气体型离子Al3+对石膏晶须的形貌无明显影响;碱土金属离子SF2+、Mg2+能够提高晶须的长度和长径比;阴离子F-不仅会引起晶须呈帚状聚集,而且会导致晶须的纯度降低.杂质离子在石膏晶须生长过程中可不同程度地进入晶格代替Ca2+或SO42-.工业上制备石膏晶须时可采用Sr2和Mg2提高晶须的长度和长径比,应避免高浓度的Na+、K+和Al3+以及F-对晶须造成的不利影响.     

柠檬酸凝胶燃烧法合成YAG:Ce,RE荧光粉及其光谱性能研究

以柠檬酸为螯合剂和燃料,采用溶胶凝胶燃烧合成法制备了一系列组成的YAG:Ce,RE(RE＝Lu,Gd,La)荧光粉.通过XRD、FTIR、SEM、荧光光谱研究了不同煅烧温度、不同共掺杂元素和浓度对荧光粉晶体结构、颗粒形貌及发光性能的影响.结果表明:在煅烧温度900℃时即可制得结晶较好的荧光粉,随煅烧温度的升高,样品的平均颗粒尺寸由50 nm左右逐渐增大到200 nm,发光强度逐渐增强.随离子的半径从La3+到Gd3+再到Lu3+逐渐减小,引起基质相变的取代上限逐渐增大,在仅有50mo1;的La3+掺杂下,样品的主晶相已经变成LaAlO3;Gd3+掺量达到90mo1;～99 mo1;时,样品主晶相仍为立方的YAG相;而Lu3+可以完全取代Y3+而仍然保持立方YAG的石榴石结构不变.当Gd3+取代Y3+时,YAG:Ce3+的发射光谱红移,未出现GdAlO3前最大红移为21 nim,完全取代后最大红移达33 nn,而Lu3+全部取代Y3+时发生24 nim的蓝移.运用晶体场理论和位形坐标模型对此进行了解释.     

B2O3对Eu2+,Dy3+共激活铝酸锶发光材料发光性能的影响

文章借助于材料的发射光谱和结晶相组成分析研究了B2O3对Eu2+,Dy3+共激活铝酸锶发光材料发光性能的影响.B2O3在Eu2+,Dy3+共激活铝酸锶发光材料的合成过程中,一方面作为助熔剂,降低发光材料的合成温度;另一方面,硼酸盐的存在促进Eu3+离子转化为Eu2+离子的还原过程.但是,B2O3加入量的变化并不引起发光材料发射光谱峰值的变化.     

表面活性剂辅助合成Y2O2S:Eu3+,Mg2+,Ti4+红色长余辉材料

以表面活性剂十二烷基硫酸钠为均匀分散剂,通过液相与固相相结合的方法制备了Y2O2S∶Eu3+,Mg2,Ti4+红色长余辉材料.采用X射线衍射(XRD)、扫描电镜(SEM)、激发与发射光谱、热释光谱等手段对材料进行了表征.研究结果表明,与高温固相法相比,样品的最低合成温度与最佳合成温度均降低了200～300℃,其发光特性没有改变,表面活性剂的添加影响了样品的形貌.同时,对表面活性剂引入后,Y2O2S∶Eu3+,Mg2+,Ti4+的生长机制和发光机理进行了讨论.     

近紫外激发Ca2 NaMg2 V3 O12:Sm3+荧光粉的制备及发光性能

近紫外激发单一基质白光发射荧光粉是当前LED用荧光转换材料的研究热点.采用高温固相反应制备了Ca2 NaMg2 V3 O12:Sm3+荧光粉,并利用X射线粉末衍射仪和荧光光谱仪等测试手段,对其物质结构和荧光性能进行了表征.探讨了(VO4)3-基团的发光机理,及其与Sm3+离子之间的能量传递机制.结果表明:Ca2 NaMg2 V3 O12:Sm3+荧光粉属于立方相晶体结构.在340 nm紫外线激发下,样品发射蓝绿光,发射最强峰位于500 nm,发射光谱覆盖整个可见光区.Sm3+离子的最佳掺杂浓度为0.03,同时(VO4)3-基团与Sm3+离子之间的能量传递主要是通过电四偶极-电四偶极相互作用来实现的.     

Intense red and cyan luminescence in europium doped silicate glasses

The photoluminescence properties of silicate glasses, singly doped with europium ions and co-doped with europium ions and Al powder, have been characterized by the absorption, excitation, and emission spectroscopies. The absorption edge in the absorption spectra shows a large red shift from 320 nm to 405 nm. Under near-ultraviolet (NUV) excitation, sample, doped with Eu³⁺ emit intense red light while those co-doped with Eu³⁺ and Al give intense cyan emission. The influences of the glass compositions on the spectroscopic properties are also discussed. These glasses may be potential candidates for light-emitting diodes (LEDs).     

XPS characterization of YAlO3:Co single crystals

YAlO₃:Co (YAP:Co) single crystals have been obtained by the Czochralski method. The XPS spectra of YAP:Co annealed in reducing atmospheres: H₂, vacuum and vacuum plus H₂ are presented and discussed. As confirmed by magnetic measurements and the electron spectroscopy XPS the dopant concentration of Co is lower than a nominal one. The annealing processes removed colour centers due to relocation and some reduction of oxygen ions in the structure. The increased unit volume during the long annealing process may be caused by the change in some Co³⁺ ions into Co²⁺ ions. This explains the occurrence of the violet colour of the longtime annealed samples. The chemical shift analysis shows more ionic bond of Y–O than Al–O. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical properties and valence change of samarium ions in a sol–gel Al2O3–B2O3–SiO2 glass by femtosecond laser irradiation

10Al₂O₃–5B₂O₃–85SiO₂–xSm₂O₃ glasses were prepared by the sol–gel method. The emission spectra of the glasses indicate that the quench concentration of the Sm³⁺ ions is about 0.2 mol%. The emission spectra of the glasses after high-temperature treatment with H₂ gas exhibit the coexistence of the Sm³⁺ and Sm²⁺ ions. We observed the strong emission line of the Sm²⁺ ions and the emission band of the non-bridging oxygen hole center when the glasses were exposed to a femtosecond laser. It indicates that some Sm³⁺ ions were reduced to Sm²⁺ ions by femtosecond laser pulses and non-bridging oxygen hole centers were formed. The ⁵D₀–⁷F₀ emission line of the Sm²⁺ ions by femtosecond laser irradiation shows a red shift, compared with the emission of the Sm²⁺ ions by reduction with H₂ gas. The strong absorption band and weak, sharp absorption lines in the range from the UV to IR come from charge transfer and the transition from the ⁶H_5/2 state to the various excited states of the Sm³⁺ ions. The reduction mechanism of Sm³⁺ ions is discussed.     

碱金属和三价Eu离子共掺杂的碱土钼酸盐荧光粉发光性能

采用固相法制备了用于白光LED的Eu3+和碱土离子(Li+,Na+,K+)共激活的钼酸盐荧光粉AMoO4(A=Ca,Sr).通过X射线衍射图片看出,Eu3+和Na+的掺入降低了晶格参数,同时衍射峰强度明显增加.本文研究了荧光粉的激发光谱和发射光谱.它的激发谱覆盖了从240nm到500nm的范围,在470nm处有一个激发峰,这说明它能够被GaN LED发出的蓝光有效激发.发射谱表明它能够发射峰值位于616nm和624nm的红光.实验研究了碱土离子的量(摩尔分数)对AMoO4:Eu3+发光性能的影响,0.25是最合适的掺杂量.反应时间和反应温度对发光性能也有很大的影响.搅拌均匀的反应物在800℃灼烧3h得到的样品发光强度最强.     

固相合成YAG微晶粉体的XRD研究

以高纯Al_2O_3和Y_2O_3超微粉为原料,通过高能球磨和固相反应法制备了Y_3Al_5O_(12)(YAG)微晶;采用X射线衍射法(XRD)研究了球磨时间、煅烧温度、保温时间等对合成YAG微晶相组成的影响.结果表明:原料粉体的粒度随研磨时间延长而降低;随煅烧温度的提高,产物的物相由Y_4Al_2O_9和YAlO_5 逐渐向YAG相转变;延长保温时间有利于Y~(3+)和Al~(3+)的扩散以及Al_2O_3和Y_2O_3的固相反应.当Al_2O_3和Y_2O_3的摩尔比为5 ∶ 3,混合粉体经过15 h的机械球磨并于1300 ℃煅烧40 min即可得到单一物相的YAG微晶粉末.     

NaMn3 F10∶Yb/（Er,Tm,Ho）纳米颗粒的制备及光谱研究

由于具有毒性低、稳定性好、发光强度高等优点,稀土上转换纳米颗粒在细胞成像和标记方面具有十分广泛的应用前景。本文采用了常规的热分解法,制备了粒径均一、均匀分散的NaMn3 F10∶Yb/( Er,Tm,Ho)上转换纳米颗粒。研究表明,制备的纳米颗粒的粒径都在10 nm以下。 NaMn3 F10∶Yb/Er和NaMn3 F10∶Yb/Tm纳米颗粒在980 nm连续激光的激发下分别发射660 nm和800 nm的单色光,这主要归因于Mn2+离子4 T1能级可以作为中间过渡能级,将Er3+离子2 H11/2能级和4 S3/2能级上的光电子通过非辐射的方式转移到2 F9/2能级上,降低2 H11/2能级和4 S3/2能级上的光电子数同时增加2 F9/2能级上的光电子数,使2 F9/2与4 I15/2基态能级产生较大的粒子数反转,以产生较强的波长为660 nm光辐射。通过对NaYF4∶Yb3+20;,Er3+2;纳米颗粒中掺杂Mn2+离子的研究发现,随着Mn2+离子掺杂浓度的提高,该纳米颗粒的发光颜色从绿色逐渐向红色转变,光谱中红绿光的强度比逐渐升高,在Mn掺杂浓度为58;时即可得到纯红光发射的上转换纳米颗粒。     

离子掺杂对纳米二氧化钛粒径的影响

本研究以工业钛液和尿素为基本原料,采用普通均匀沉淀法制备出单分散的锐钛矿型的球形纳米TiO2,研究了La3+、Fe3+、Co2+、Al3+四种离子不同掺杂量对纳米TiO2粒子粒径的影响,并对其机理进行了分析.研究结果表明,离子掺杂可以显著细化纳米TiO2的粒径,且掺杂后的TiO2仍为锐钛矿型.没有发现掺杂离子的特征峰,可以认为离子掺杂属于替位掺杂.     

燃烧法制备掺杂Y改性LaMgB5O10粉体及表征

以水合硝酸镧(La(NO3)3·nH2O)、六水硝酸镁(Mg(NO3)2·6H2O)为氧化剂,甘氨酸(C2H5NO2)为还原剂,掺杂氧化钇(Y2O3)粉体,通过燃烧法合成掺杂Y改性的硼酸镁镧(LaMgB5O10)粉体.研究了Y的掺杂量、焙烧温度和时间等工艺参数对合成Y改性LaMgB5O10的影响.通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、荧光光谱(PL)、紫外-可见漫反射光谱(UV-Vis DRS)等手段对产物进行表征.结果表明,当Y的掺杂量为5;,焙烧温度900 ℃,焙烧时间5 h时,Y改性LaMgB5O10效果最佳.Y改性LaMgB5O10在212~317 nm处出现了很强的紫外吸收峰;在280~355 nm和368~435 nm处有很强的发射宽峰.     

Optical properties of fluorine-substituted zinc bismuth phosphate glasses

The effects of the substitution of fluoride ions for oxide ions on the thermal and optical properties of ternary ZnO-Bi₂O₃-P₂O₅ glass with low-P₂O₅ content (20-25 mol%) were investigated. Fluoride ions were introduced into the glass up to about 12 mol% as ZnF₂. Raman spectra indicated that fluoride ions were substituted for oxide ions connected with bismuth ions. Deformation and glass transition temperatures decreased monotonically with fluorine concentration. The absorption edge shifted toward higher energies with increasing fluorine concentration by about 0.3 eV for 12 mol% ZnF₂ substitution. The blue shift of the absorption edge is attributable to two effects. One was a blue shift of an absorption band which was observed as a peak at 4.7 eV in the reflection spectra and was attributed to the spin forbidden 6s-6p interband transition in Bi³⁺ ions. The blue shift originates from a change in electron-donating ability through anions as expected from electronegativity or optical basicity. Another is a disappearance of a shoulder at around 4.3 eV in the reflection spectra. The latter was the major reason for the large blue shift of the absorption edge energy, because the band relating to the 4.3 eV shoulder is close to the absorption edge.     

Effects of yttrium codoping on fluorescence lifetimes of Er3+ ions in SiO2–Al2O3 sol–gel glasses

In order to find a new glass host and optimize erbium doping for IR glass optical amplifiers in photonic applications, a study on the optimization of the emission of erbium ions in the SiO₂–Al₂O₃ glass by codoping with Y₂O₃ is performed. It is first attempted to make a new sol–gel glass host based on SiO₂, Al₂O₃, and Y₂O₃ doped with Er³⁺ ions of the composition (1−x)SiO₂–xAl₂O₃–yY₂O₃:0.65Er₂O₃ (in mol%), x varies from 0 to 65, and y from 0 to 4. The optimal proportion in mol% of SiO₂ and Al₂O₃ for the Er³⁺ emission (at a fixed optimal concentration of 0.65) was 65 – 35. The effect of Y₂O₃ content on photoluminescence, decay curve profiles and lifetime of the ⁴I_13/2 level of Er³⁺ in SiO₂–Al₂O₃ glass is observed. The largest quantum efficiency and the higher emission intensity are observed in the sample with 65Al₂O₃ and 4Y₂O₃. The emission intensity at 1530 nm is two times higher than in glasses without Y₂O₃. A shift of 3 nm to shorter wavelengths is observed. The emission spectral profiles are flatter and broader for the glasses containing Al and Y (bandwidth of 59.5 nm). The decay curves show strong difference profiles for the different samples. The increase of the lifetime value τ (about ms) of the ⁴I_13/2 level of Er³⁺ in the SiO₂–Al₂O₃ with the Y₂O₃ is discussed.