Novel Red-Emitting Microwave-Assisted-Sintered LiSrPO4: Eu3+ Phosphors for Application in Near-UV White Light-Emitting Diodes

Novel red-emitting LiSr_1?x PO₄:xEu³⁺ phosphors with various concentrations (x = 0.03, 0.05, 0.07, 0.1) of Eu³⁺ ions were synthesized by microwave-assisted sintering at 1200°C for 3 h in air. The microstructural and luminescent characteristics of the LiSrPO₄:Eu³⁺ phosphors were investigated and are discussed here. x-Ray diffraction (XRD) results showed that the prepared LiSr_1?x PO₄:xEu³⁺ phosphors presented an impurity phase of Eu₂O₃ when the Eu³⁺ ions exceeded x = 0.05. Photoluminescence (PL) results showed a series of emission states ⁵D₀ → ⁷F₀, ⁵D₀ → ⁷F₁, ⁵D₀ → ⁷F₂, ⁵D₀ → ⁷F₃, and ⁵D₀ → ⁷F₄ (corresponding to the typical 4f → 4f intraconfiguration forbidden transitions of Eu³⁺) with a major emission peak at around 617 nm. The optimum concentration of Eu³⁺ for LiSr_1?x PO₄:xEu³⁺ prepared by microwave-assisted sintering was found to be 0.05. The lifetime values of LiSr_1?x PO₄:xEu³⁺ phosphors with doping concentrations of Eu³⁺ ions of 0.03, 0.05, 0.07, and 0.1 were found to be 3.32 ms, 3.30 ms, 2.84 ms, and 2.60 ms, respectively. Moreover, the chromaticity values (x, y) of all of the LiSr_1?x PO₄:xEu³⁺ phosphors were located in the red region (0.65, 0.34).     

Hydrothermal Synthesis and Luminescent Properties of BiPO4:Eu3+ Phosphors

In this study, BiPO₄:Eu³⁺ phosphors were synthesized by a facile hydrothermal route at different temperatures. The BiPO₄:Eu³⁺ particles were characterized by x-ray powder diffraction (XRD), infrared spectra, and luminescence spectroscopy. The XRD results reveal that the BiPO₄:Eu³⁺ particles present different phases for different hydrothermal temperatures. It is found that a hexagonal phase is formed at 100°C, which transforms to a low-temperature monoclinic phase (MP) when the hydrothermal temperature is increased to 150°C. This low-temperature MP transforms to high-temperature MP when the temperature is increased beyond 200°C. The luminescent properties of the BiPO₄:Eu³⁺ particles were studied using an excitation wavelength of 270 nm. The emission spectra display the bands associated with the ⁵D₀ → ⁷F _J (J = 1, 2, 3, and 4) electronic transitions of the Eu³⁺ cations. The intensity of the emission spectra increases with increasing hydrothermal temperature. These results demonstrate that BiPO₄:Eu³⁺ with different phases can be obtained through the hydrothermal method, which may enrich the solution chemistry for preparation of advanced materials with tailored functionality.     

燃烧合成法制备的BaFBr:Eu2+的性质研究

BaFBr：Eu^2 是一种性能优良的光激励发光材料，它能够存储X光信息，并通过可见光激励发光读出存储的光信息．当前广泛用于医疗和工业设备上。BaFBr：Eu^2 的传统制备方法是高温固相法，文章介绍了应用燃烧合成法，采用尿素一硝酸盐系燃烧合成获得BaFBr：Eu^2 ，分别利用XRD和分光光度计对产物的各种性质进行测量研究。燃烧合成法一直应用在合成金属氧化物和难熔金属之间的合成上，制备BaFBr：Eu^2 这类不含氧的化合物还未见报道。实验结果表明，利用燃烧合成法制备BaFBr：Eu^2 可以大幅度减少制备时间和能源的消耗，而且晶相单一，发光强度可以达到高温固相法的水平。     

Hydrothermal Synthesis of SrMoO4:Eu3+, Sm3+ Phosphors and Their Enhanced Luminescent Properties Through Energy Transfer

Eu³⁺ and Sm³⁺ co-doped SrMoO₄ phosphors have been successfully prepared via a simple surfactant-free hydrothermal method. The as-prepared phosphors present dumbbell-like agglomerates and comprise of many nanoparticles of 150–300 nm in diameter. Eu³⁺ and Sm³⁺ co-doped SrMoO₄ phosphors display all the characteristic excitations and emissions of Eu³⁺ and Sm³⁺. The introduction of Sm³⁺ can generate a strong excitation line at 403 nm, originating from the ⁶H_5/2 → ⁴K_11/2 transition of Sm³⁺, which significantly broadened the excitation region for matching the near ultraviolet light emitting diodes (～400 nm). And Sm³⁺ ions can transfer the absorbed energy to Eu³⁺ ions efficiently, so the intensity of the main emission peak at 614 nm due to ⁵D₀ → ⁷F₂ transition of Eu³⁺ are strengthened by the co-doping of Sm³⁺. The doping concentration of Eu³⁺/Sm³⁺ was optimized. In addition, the possible energy transfer mechanism has been investigated and is discussed in detail.     

Microwave Sintering and Optical Properties of Sm3+-Activated KSrPO4 Phosphors

The microwave sintering and photoluminescence properties of KSr_1?x PO₄:xSm³⁺ phosphors have been investigated. KSrPO₄ phosphates activated by various concentrations of Sm³⁺ ions (x = 0.007, 0.009, 0.01, 0.03) were microwave sintered at 1200°C for 3 h under air atmosphere. x-Ray diffraction patterns showed that all phosphor samples exhibited a single phase without any extraneous phases. Scanning electron microscopy images showed that the particle size increased with the Sm³⁺ concentration and that the particle morphology was fine and uniform. The photoluminescence results showed that a concentration quenching effect occurred when the concentration of Sm³⁺ ions reached x = 0.01. Decay time measurement results showed that the lifetime decreased gradually from 3.12 ms to 2.34 ms as the Sm³⁺ concentration increased. All the chromaticity (x, y) values of the microwave-sintered KSrPO₄:Sm³⁺ phosphors were located in the red region (0.57, 0.41).     

白光有机电致发光显示器件的特性与制备方法的研究

有机电致发光显示器因其高亮度、低功耗、结构简单、响应快、视角宽等优点而愈来愈受到大家的青睐.利用白色OLED是一种实现全彩色显示的方法,因为白光加滤色膜的方式可以获得红、绿、蓝三基色.文章采用双发光层方法,即TBPe掺杂到ADN中作为蓝色发光层,DCJ TB掺杂到Alq3中作为红色发光层,从而实现白光显示.该制作工艺简单、容易控制、实验可重复性比较高,且色度比较稳定,随电压的变化幅度较小,最佳色度为(0.3345,0.333),几乎与标准白光色度重合.     

White ACPEL Device with ZnS:Cu,Cl, Tb3Al5O12:Ce3+, and CaS:Eu2+ Phosphors Using a Layered Structure

Improvement of the color rendering index (CRI) and luminance of a white alternate current powder electroluminescent (ACPEL) device has been attempted using ZnS:Cu,Cl, Tb₃Al₅O₁₂:Ce (TAG:Ce), and CaS:Eu phosphors with a layered structure. The device with TAG:Ce and ZnS:Cu,Cl phosphors showed a CRI of 75, with a luminance increase of about 30% depending on the thickness of the TAG:Ce. Further CRI improvement was attempted using CaS:Eu. When they were separately screen‐printed, the CRI was increased up to 89 with no decrease in luminance.     

Optical and Electrical Properties of Cu2ZnSnS4 Film Prepared by Sulfurization Method

Cu₂ZnSnS₄ (CZTS) films were prepared by sulfurization of sputtered Zn/Sn/Cu multilayer thin films. Raman peaks at 251 cm^?1, 289 cm^?1, 336 cm^?1, and 362 cm^?1 were detected, and the optical band gap energy of the CZTS was estimated to be about 1.53 eV. Energy-dispersive spectrometry and x-ray photoelectron spectroscopy reveal that the composition ratio of prepared CZTS film is close to stoichiometric. Photoresponse current measurements show persistent photoconductivity effect, with decay constants τ and β of 5.04 and 0.269, respectively.     

蓝色长余辉材料SrAl4O7:Eu2 ,Dy3 的合成及其发光特性

为了进一步探索铝酸盐系列长余辉材料的显色范围,改善其粉体特性,采用铝酸盐阳离子草酸盐共沉淀及湿法混合原材料方法,在传统绿色长余辉荧光粉SrAl2O4Eu2+,Dy3+合成的基础上,增加基质Al的比例,并由通常α-Al2O3改成AlCl3·6H2O,选用硼酸氨与氟化铝为助溶剂,成功合成了高效、低硬度和细粒径良好粉体特性的浅蓝色长余辉发光材料SrAl4O7Eu2+,Dy3+.测量了样品的X射线衍射(XRD)图谱、激发与发射光谱、余辉衰减曲线及热释光谱图等,并对其进行了分析.结果表明,Eu2+在这两种基质中均存在2个发光中心,其衰减速度不一样,蓝发光中心寿命要远大于绿发光中心寿命.相对SrAl2O4Eu2+,Dy3+而言,SrAl4O7Eu2+,Dy3+发射光谱峰值从520 nm蓝移至480 nm,衰减到可辨认发光强度0.32 mcd/m2的余辉时间从30 h延长到60 h以上,且合成样品表现出更好的结晶状态、分散性及较小的中心粒径.     

电子俘获材料KCl:Eu2+的光存储特性研究

采用高温固相反应法制备出了粉末态的 KCl:Eu2 样品 ,研究了 Eu掺杂浓度与光激励发光的关系。测试了样品的发光性能和存储性能 ,并分析了 KCl:Eu2 的光存储的机制。     

溶胶-凝胶法制备掺Er3+:Al2O3/SiO2/Si光波导薄膜

采用溶胶-凝胶(Sol-gel)法在热氧化的SiO2/Si(100)基片上提拉法制备掺EP:A12O3光学薄膜.采用扫描电镜(SEM)、原子力显微镜(ARM),X射线衍射分析(XRD)研究了掺Er3+:Al2O3光学薄膜的形貌、厚度以及结构等特性.结果表明,在氧化的SiO2/Si(100)基片上获得了厚度为1.2 μm,固溶Er3+的面心立方结构γ-(Al,Er)2O3和单斜结构θ-(A1,Er)2O3的薄膜.薄膜表面光滑、平整,无明显的表面缺陷.掺EP:Al2O3薄膜晶粒分布均匀,平均晶粒直径为50～200 m,表面起伏度为10～20 nm.测量了10 K下掺0.1 mo1%～1.5 mo1%Er3+:Al2O3光学薄膜的光致发光(PL)谱,获得了中心波长为1.533μm的发光曲线.PL强度随Er3+掺杂浓度的增加而下降,相应的半峰宽(FWHM)也从45 nm减小到36 nm.Sol-gel法制备掺Er3+:Al2O3/SiO2/Si光学薄膜满足有源光波导放大器基体材料的性能要求.     

斜角入射沉积TiO_2薄膜的光学特性和表面粗糙度

采用电子束热蒸发技术在K9玻璃基底上以不同的沉积入射角沉积了单层TiO2薄膜,研究了不同入射沉积角沉积的TiO2薄膜的光学特性、填充密度和表面粗糙度,并比较了不同膜层厚度下薄膜表面粗糙度与入射沉积角之间的关系。研究结果表明,随着入射沉积角的增加,TiO2薄膜的透射率增加,透射峰值向短波移动,薄膜的填充密度从入射沉积角0°时的0.801降低到入射沉积角为75°时的0.341;薄膜的表面粗糙度随着入射沉积角的增加而增加,当入射沉积角为75°时,薄膜的表面粗糙度略高于基底的表面粗糙度。在沉积入射角不变时,随着膜层厚度的增加,膜层的表面粗糙度降低。     

等离子显示屏(PDP)用新型红色发光体的合成及光学特性

为开发出等离子显示屏用新型红色荧光体，研究了GdAl3(BO3)4:Eu，Gd2SiO4：Eu的紫外和真空紫外发光特性。在147nm激发下GdAl3(BO3)4：Eu^3 呈色坐标为(0．645，0．330)的强红光发射，说明是非常有前途的PDP用红色发光材料。在GdAl3(BO3)4：Eu^3 的激发光谱中，除观察到Eu^3 的电荷迁移带(峰值位于258nm)外，还观察到峰值位于155nm的宽带。依据硼酸盐的吸收数据将其归属于BO3基团的吸收。另外观察到Gd^3 8S7/2→^6I11/2跃迁(274nm)及在真空紫外(158～160nm)激发下，Eu^3 的红光发射强度随着Eu^3 浓度的增加而减弱，说明BO3基团吸收的能量经Gd^3 为媒介转移到Eu^3 。分析Gd2SiO5：Eu的激发光谱，得到Eu^3 的电荷迁移带是峰值位于256nm的宽带，峰值位于183nm的宽带可能是Gd^3 的电荷迁移带。在256nm激发下Gd2SiO5：Eu^3 呈强红光发射，但是147nm激发下很弱。这是由于真空紫外激发效率低的原因，其特点可由其晶体结构即激活离子所处的环境解释。     

发光体MAl2O4:Eu2+,RE3+的长余辉形成机理

提出了Eu^2 激活的MAl2O4:Eu^2 ,RE^3 （M＝Ca,Sr,Ba;RE=Dy,Nd,Ho,Er,Pr,Tb等稀土元素）系列铝酸盐发光体的长余辉发光机理。认为O^2-空位Vo是一种电子俘获陷际，是形成余辉的根本原因，RE^3 的引入使陷阱深度适宜而使余辉时间延长。缺陷在晶格中成簇分布，Vo和碱土金属离子空位VM在高温下可相互缔合。利用电子陷阱模型解释了实验中的一些普遍现象并提出了固相反应法合成此类发光体的工艺改进措施。     

利用时域有限差分法进行光波导器件的仿真

将理想匹配层（PML）吸收边界条件用于平面光波导结构的时域有限差分法（FDTD）分析，并对微腔体谐振环进行了数值计算模拟。证明了采用PML吸收边界条件的FDTD法应用于平面光波导结构分析的有效性。本方法对平面光波导的计算机辅助设计（CAD）具有实际意义，可用于分析任意复杂结构的平面光波导。     

掺杂Au和Co的In2O3纳米粉体的微乳液法制备及其气敏特性

在油包水(W/O)型微乳液体系中,通过In(NO3)3、Co(NO3)2、HAuCl4和(NH4)2CO3之间的共沉淀反应,制备了掺钴和金的纳米氧化铟的前驱体.对前驱体经300℃焙烧后所得的粉体进行了XRD表征和气敏性测试.结果表明,制得的氧化铟粉体为立方晶相,随着钴和金掺杂量的增大,样品的晶粒度逐渐减小;同时掺杂1mol%的Co和1mol%的Au的氧化铟气敏元件对CO气体敏感性有较大提高,灵敏度达到25.9,而且具有较高的选择性.     

溶胶-凝胶法制备ITO薄膜及其光电性能的研究

采用溶胶-凝胶工艺,用提拉法在玻璃基底上制备了ITO透明导电薄膜。使用四探针测试仪和紫外可见光分光光度计测量薄膜的方阻和透过率,并采用XRD、SEM等测试手段对薄膜的晶体结构、表面形貌进行了表征。结果表明,掺锡比例和热处理温度对薄膜的导电性具有重要影响,在掺Sn量为15%(原子分数比)、450℃热处理时薄膜的方阻最小;薄膜的透过率曲线随掺锡比例的增加向紫外方向移动。随着热处理时间、镀膜层数的增加,薄膜的方阻先减小,最后趋于一稳定值,在可见光范围内薄膜的透过率变化较小。