Study on preparation and luminescent properties of Eu3+-doped LaAlO3 and GdAlO3

Eu³⁺-doped trigonal LaAlO₃ and orthorhombic GdAlO₃ phosphors have been successfully synthesized by sol–gel method. The crystallization processes of the phosphors have been characterized by X-ray diffraction (XRD) and thermogravimetry-differential scanning calorimetry (TG-DSC). The optical properties of these phosphors were investigated using the photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The influences of the different structures and bonding of the hosts on the luminescence performance of Eu³⁺ ion-doped LaAlO₃ and GdAlO₃ were investigated in detail based on chemical bond theory. Under appropriate UV-radiation, the reddish orange light emitted from GdAlO₃:Eu³⁺ was brighter than that from LaAlO₃:Eu³⁺. Such a brightly luminescent phosphor could be considered as an ideal optical material for the development of new optical display systems.     

Co-precipitation synthesis and luminescent properties of indium-substituted YAG: Ce3+

Cerium-doped yttrium aluminum indium garnet (YAG: Ce³⁺) yellow phosphor was prepared by using the co-precipitation method. The impacts of In³⁺ concentration onto the properties were investigated and analyzed by X-ray diffraction, infrared spectra, scanning electron microscopy, and X-ray photoelectron spectroscopy. The results indicated that the co-precipitation method adopted favored the ultrafine powders and achieved In³⁺ substitution for part of Al³⁺, leading to the large crystal plane spacing, and a blue shift occurred in the indium-substituted YAG: Ce³⁺ emission.     

共沉淀法制备YAG超细粉及透明陶瓷

研究了共沉淀法制备YAG透明陶瓷的工艺。采用Al(NO3)3和Y(NO3)3的混合溶液为母盐,以碳酸氢铵为沉淀剂,采用共沉淀法制备了化学组成为Y2(CO3)3·nH2O+NH4AlO(OH)HCO3的碳酸盐先驱沉淀物。使用透射电镜和X射线衍射对先驱沉淀物的形貌及煅烧过程的相转变进行了研究。结果表明先驱沉淀物在900℃煅烧2h后完全转变为YAG相。1100℃煅烧后得到的YAG粉体具有良好的烧结性能。使用0.5%(质量分数)的TEOS(正硅酸乙酯)作为烧结添加剂,1700℃真空烧结5h后,得到了透明YAG烧结体。     

掺杂浓度对Al2O3:Ce3+薄膜发光性能的影响

应用中频反应磁控溅射技术在载玻片上制备掺铈的Al2O3薄膜,在固定的电源功率下,氩气流量为43ml/min,氧流量为10ml/min,室温下溅射时间为90min的条件下,通过控制薄膜中的Ce3 离子的掺杂量来改变薄膜的发光性能.通过X光能量散射谱(EDS)和光致发光测量,得到发光强度和发光峰位对薄膜中的Ce3 浓度有强烈的依赖关系,并且分析了产生这种关系的原因;对发光激发谱分析表明,薄膜发光是源于薄膜中形成的氯化铈集合体中的Ce3 .Al2O3:Ce3 发光膜可应用于需要蓝光发射的平板显示领域.     

Synthesis of novel halloysite@YF3:Ce3+,Tb3+ nanocomposite for enhanced luminescent properties

A novel halloysite@YF₃: Ce³⁺, Tb³⁺ anocomposite with strong luminescent properties was designed and synthesized by a facile direct precipitation strategy. Owing to the halloysite as a support, it can significantly prevent the aggregation of YF₃:Ce³⁺,Tb³⁺ and the distribution of YF₃:Ce³⁺,Tb³⁺ on halloysite was highly uniform. Importantly, due to the unique surface-interface-dielectric multiple confinement (SIDMC) effects, the as-harvested halloysite@YF₃:Ce³⁺,Tb³⁺ nanocomposite exhibited excellent luminescent performance. Compared with YF₃:Ce³⁺,Tb³⁺, the luminescence intensity of halloysite@YF₃:Ce³⁺,Tb³⁺ nanocomposite is significantly enhanced by about 6 times under 255 nm excitation. However, the fluorescence lifetime of halloysite@YF₃:Ce³⁺,Tb³⁺ nanocomposite (7.21 ms) is shorter than that of YF₃:Ce³⁺,Tb³⁺ nanoparticles (8.34 ms). This finding indicated that halloysite can change the luminescent properties of YF₃:Ce³⁺,Tb³⁺ nanoparticles through an SIDMC effect. The combination of halloysite and YF₃:Ce³⁺,Tb³⁺ nanoparticles not only endowed halloysite with special properties, and effectively tuned the luminescent properties of YF₃:Ce³⁺,Tb³⁺ nanoparticles, thereby improving the utility of halloysite and YF₃:Ce³⁺,Tb³⁺ nanoparticles. The research supplies an insight on the development of natural mineral-based luminescent materials, and hopefully it could promote them application in many fields.     

Microwave dielectric properties of B2O3 doped LaAlO3 ceramics at low sintering temperature

The microwave dielectric properties and the microstructures of LaAlO₃ ceramics with B₂O₃ additions (0.25–1 wt%) prepared with conventional solid-state route have been investigated. Doping with B₂O₃ (up to 0.5 wt%) can effectively promote the densification of LaAlO₃ ceramics. It is found that LaAlO₃ ceramics can be sintered at 1400°C due to the liquid phase effect of B₂O₃ addition. The Q × f value as well as the dielectric constant decreases at higher B₂O₃ doping level (1 wt%) due to the increase of boundary phases. At 1460°C, LaAlO₃ ceramics with 0.5 wt% B₂O₃ addition possesses a dielectric constant ( _r ) of 22.9, a Q × f value of 44700 (at 9 GHz) and a temperature coefficients of resonant frequency ( _f ) of –36 ppm/°C. The B₂O₃-doped LaAlO₃ ceramics can find applications in microwave devices requiring low sintering temperature.     

La(BO_3,PO_4):Ce,Tb,Gd的发光研究

以 BPO4和稀土氧化物为原料制备了铈、铽、钆共掺杂的硼磷酸镧绿色荧光粉,研究了基质中 Gd3＋、 Ce3＋、 Tb3＋的发光特性及它们之间的相互作用。在该基质中存在 Ce3＋→ Gd3＋、Gd3＋→ Tb3＋、 Ce3＋→ Tb3＋的能量传递;当钆加入到铈、铽共掺杂的硼磷酸镧基质中会导致铈离子的发射减弱,铽离子 5D4→ 7FJ的发射显著增强,而 5D3→ 7FJ的发射没有明显变化,故有利于提高荧光粉的发光强度和绿色发射纯度。用硼磷酸钆作基质比用硼磷酸镧更能提高荧光粉的发光强度、发光纯度以及发光色坐标 x的值,所以 La(BO3,PO4):Ce,Tb,Gd和 Gd(BO3,PO4):Ce,Tb均是理想的绿色发射材料。     

掺杂浓度对中频反应磁控溅射制备Al2O3:Ce3+薄膜发光性能的影响

应用中频反应磁控溅射设备在载玻片上制备掺铈的Al2O3薄膜,在固定的电源功率下,氩气流量为23sccm,氧流量为5sccm,室温下溅射时间为90min的条件下,通过控制薄膜中的Ce^3＋离子的掺杂量来改变薄膜的发光性能。通过X光能量散射谱（EDS）和光致发光测量,得到发光强度和发光峰位对薄膜中的Ce^3＋浓度有强烈的依赖关系,并且分析了产生这种关系的原因;对发光激发谱分析表明,薄膜发光是源于薄膜中形成的氯化铈集合体中的Ce^3＋。Al2O3：Ce^3＋发光膜可应用于需要蓝光发射的平板显示领域．     

Fabrication and properties of highly transparent Er:YAG ceramics

Highly transparent Er:YAG ceramics with different Er doping concentrations were fabricated by a reactive sintering method under vacuum. The optical properties and the microstructures of the Er:YAG ceramics were investigated. For 3 mm thickness samples, the in-line transmittances of the as-fabricated Er:YAG ceramics at the wavelength of 1100 nm and 400 nm were about 84% and 82%, respectively. The micrograph of the Er:YAG transparent ceramics exhibited a pore-free structure and the average grain size was about 10 μm. The grain boundary of the ceramics was clean and no secondary phase was detected. The absorption and emission spectra, the fluorescence decay traces of the Er:YAG ceramics were measured and discussed. The ceramics obtained may have potential use for eye-safe solid-state lasers partly replacing Er:YAG single crystals.     

Fabrication and laser properties of transparent Yb:YAG ceramics

High optical quality transparent Yb:YAG laser ceramics have been successfully fabricated by a vacuum reactive sintering method. Commercial Al₂O₃ powder and co-precipitated Y₂O₃ and Yb₂O₃ powders were used as the raw materials. In-line transmittances at 1300 nm and 400 nm were measured to be 83.6% and 81.8% respectively for a 3 mm thick mirror polished Yb:YAG ceramics sample. Continuous wave (CW) lasing at the wavelength of 1030 nm was achieved when pumped by a 940 nm fiber coupled laser diode. A slope efficiency as high as 62.7% was obtained.     

掺杂浓度对中频反应磁控溅射制备Al2O3:Ce3+薄膜发光性能的影响

应用中频反应磁控溅射设备在载玻片上制备掺铈的Al2O3薄膜,在固定的电源功率下,氩气流量为23sccm,氧流量为5sccm,室温下溅射时间为90分钟的条件下,通过控制薄膜中的Ce3+离子的掺杂量来改变薄膜的发光性能.通过X光能量散射谱(EDS)和光致发光测量,得到发光强度和发光峰位对薄膜中的Ce3+浓度有强烈的依赖关系,并且分析了产生这种关系的原因;对发光激发谱分析表明,薄膜发光是源于薄膜中形成的氯化铈集合体中的Ce3+.Al2O3:Ce3+发光膜可应用于需要蓝光发射的平板显示领域.     

掺铕氧化钇发光纳米晶的拉曼光谱研究

采用凝胶燃烧法制备了8～50nm的Y2O3:Eu3+纳米晶.利用XRD确定了纳米晶的结构及晶粒大小,测定了不同晶粒大小的纳米晶Y2O3:Eu3+的拉曼光谱.通过测定不同的激发光所激发的拉曼光谱,以及比对荧光谱,指认了纳米晶Y2O3:Eu3+的Raman振动光谱,并且观察和研究了Raman光谱随晶粒尺寸的变化,发现了低维材料的一些反常拉曼效应.     

Influence of Ce3+ on dielectric properties of tungsten bronze structured PBN ceramics

The effect of A-site substitution of Ce³⁺ in tungsten bronze structured PBN ceramics with the general formula, Pb_{(x − 3y/2)}Ce _y Ba_(1 − x)Nb₂O₆ and the stoichiometric chemical formula, Pb_{(0.65 − 3y/2)}Ce _y Ba_0.35Nb₂O₆, where y = 0, 2, 4, 6, 8 and 10 mol% ceramic compositions synthesized through solid state reaction method are reported. The X-ray diffraction studies exhibited the presence of an orthorhombic phase, and its intensity increased with the increasing Ce³⁺ content up to y = 6 mol% or A₃ composition. The lattice parameters, unit cell volume and density as a function of Ce³⁺ concentration are discussed. It is observed that increasing Ce³⁺ content in A-site influenced the dielectric properties. The optimum dielectric properties of room temperature dielectric constant (ε_RT) and dielectric maximum () are observed in y = 6 mol% or A₃ composition while Curie temperature (T _c) and dielectric loss (tan δ) constantly decreased from undoped to y = 10 mol%, and thus A₃ composition or 6 mol% Ce modified tungsten bronze structured-PBN could be suitable for capacitor applications.     

Preparation and luminescent properties of GdOF:Ce,Tb nanoparticles and their transparent PMMA nanocomposites

GdOF:Ce, Tb nanoparticles and their poly (methyl methacrylate) (PMMA) nanocomposites have been successfully prepared by a thermolysis route and thermal polymerization of methyl methacrylate (MMA) monomer, respectively. The obtained nanoparticles and nanocomposites are characterized by XRD, EDS, TEM, FTIR, TGA, UV–Vis and PL spectrum. The as-synthesized transparent GdOF:Ce, Tb/PMMA nanocomposites exhibit green photoluminescence under the irradiation of 254 nm UV lamp due to the incorporation of luminescent GdOF:Ce, Tb nanoparticles into the PMMA matrix. The present route would provide a general strategy to prepare other functional nanocomposites.     

Synthesis and photoluminescence properties of Ho3+ doped LaAlO3 nanoparticles

Nanosized particles with different Ho3+ concentrations were synthesized in LaAlO3 lattices using a simple Pechini-type sol-gel method. X-ray diffraction measurements were used to investigate the structural composition and the effects of holmium dopant concentration on LaAlO3:Ho3+ crystal formation. Field-emission scanning-electron microscopy images confirm the formation of approximately spherical particles with an average size about 100 nm. The photoluminescence results yielded optimal holmium ion concentration in LaAlO3 host matrices was about 3% in mol equivalent. The mechanism that are responsible for the photoluminescence emission processes discussed with the help of Ho3+-ion Dieke energy level diagram. Power dependent slope measurements were performed to identify up-conversion photoluminescence process involved in LaAlO3:Ho3+.     

Al_2O_3:Ce~(3+)薄膜发光特性研究

用中频反应磁控溅射技术制备了Al2O3:Ce3+的非晶薄膜。这些薄膜的光致发光峰是在370～395 nm之间,它来自于Ce3+离子的5d1激发态向基态4f1的两个劈裂能级的跃迁。发光强度依赖于薄膜的掺杂浓度,并分析了产生这种关系的原因。Al2O3:Ce3+非晶薄膜发光特性在平板显示等领域有着广泛潜在的应用前景。     

紫外发射荧光粉SrCO_3:Ce~(3+)的制备及其发光性质

采用微波辅助共沉淀法制备紫外发射荧光粉Sr1-xCO3:xCe3+,并利用扫描电镜、激光粒度测试、X射线衍射和荧光光谱等分析手段分别对样品SrCO3:Ce3+的形貌、粒径、物相和发光性能进行表征。结果表明:掺杂Ce3+作为发光中心进入到纯斜方晶系碳酸锶晶格中,没有导致晶体结构的变化;样品呈类球状分布,粒径范围3~8μm,中值粒径d50=5.518μm;以254、327 nm波长激发均产生峰值位于354、378 nm的宽发射谱带,位于近紫外发射区,可以应用于黑光灯等;随着Ce3+离子掺杂浓度的增大,发光强度先增加后减小,其淬灭浓度为1.5%(摩尔分数);根据Dexter理论得出样品的浓度猝灭机理为电偶极-四极相互作用。     

BaTiO3陶瓷中Gd、Ce的掺杂效应研究

在BaTiO3(BT)-Nb2O5-ZnO系统中引入硼硅酸盐助烧剂,加入Gd、Ce稀土氧化物以期获得中温烧结X7R陶瓷材料.研究发现,随着Gd用量的增加,单独掺杂时陶瓷室温介电常数先减小后增大,而与Ce复合掺杂时室温介电常数单调递增,分析认为,这是由于Gd在BT晶粒中对A位和B位的不同取代造成;随着Ce掺杂量的增大,室温介电常数减小,这与壳芯结构理论吻合.SEM图分析发现,Gd、Ce共掺杂BT陶瓷晶粒生长明显大于单独掺Gd或Ce的BT陶瓷,且陶瓷气孔率低,致密化程度高.