Eu3＋离子掺杂纳米TiO2的制备及发光性能的研究

采用溶胶一凝胶法制备了TiO2和Eu3 离子掺杂的TiO2纳米材料,通过X射线衍射和荧光光谱分析对样品进行了表征.X射线衍射结果表明,少量稀土Eu3 离子的掺杂能有效抑制TiO2纳米颗粒的增长,进而提高晶体相变温度;荧光光谱研究表明TiO2:Eu3 体系中均能得到Eu3 离子特征发射光谱.随着Eu3 离子含量的增加,Eu3 离子的发光性能增强;并且Eu3 离子以Eu2(樟脑酸)3(1,10-菲咯啉)2有机配合物为前驱体掺杂到TiO2:Eu3 纳米晶体的发光性能优于以Eu(NO3)3·6H2O为前驱体制备的TiO2:EU3 纳米晶体.     

Y2O3∶Eu3+纳米管阵列的荧光和拉曼光谱研究

用电场辅助电沉积的方法,在多空有序氧化铝模板(AMM)中成功合成了Eu3 掺杂的Y2O3纳米管阵列.扫描电镜和透射电镜观察表明这些稀土化合物纳米管是均匀、连续的、且相互平行.纳米管的外径大约60nm、壁厚3nm.实验中得到的全是纳米管,没有发现纳米丝.XRD、Raman光谱、XPS和荧光光谱表明Eu3 离子确实进入了晶格.大部分Eu3 离子占据缺少反对称中心的C2位置,只有少量的Eu3 离子占据具有对称中心的S6位置.在394nm波长的紫外光激发下,Y2O3纳米管阵列的发射光谱仅在612nm处有一个峰,这对应于Eu3 中电子的5D0→7F2跃迁.当Eu3 与Y3 的摩尔比为7.5%时,纳米管阵列的发光最强.     

低温共沉淀法合成红色荧光粉CaCO3:Eu3+

采用低温共沉淀法直接合成红色荧光粉CaCO3:Eu3+,利用X射线衍射(XRD),电子扫描电镜(SEM)和荧光光谱(PL-PLE)等仪器对样品的结构、形貌和发光性质进行表征.同时,研究了反应温度和Eu3+离子掺杂量对样品性能的影响.结果表明:通过改变工艺条件可以合成球形、立方体和针状等不同形貌的样品.Eu3+作为发光中心进入到文石型或方解石型CaCO3的晶格中,其最佳掺杂量1.0%(摩尔分数).激发峰主要由电荷迁移态和Eu3+离子的特征激发跃迁组成.发射峰以电偶极跃迁5D0→7F2为主,Eu3+离子未处于严格对称的格位.样品的形貌,结晶度和物相均对发光强度有较大的影响,光滑的针状的文石型样品的发光强度最高.反应温度不同,样品的发光强度不同,其最佳的反应温度为60℃.     

ABAlO4:Eu3+（A=Ca,Sr;B=Y,Gd）荧光粉的制备及其发光性能

采用高温固相法制备了荧光粉ABAlO4:Eu3+(A=Ca,Sr;B=Y,Gd),利用X射线粉末衍射(XRD),荧光光谱对样品的相纯度,激发光谱和发射光谱进行了表征与分析。样品中Eu3+离子的电荷迁移带和f-f跃迁被归属和讨论,激发和发射光谱显示样品能够有效地被紫光397nm激发,呈现典型的红光发射(622nm)。研究表明该荧光粉是一种潜在的白光LED用荧光体转换荧光材料。     

共沉淀法制备Cs2Ag0.1Na0.9BiCl6:Tm3+双钙钛矿及其近红外发光性能

间接带隙的Cs₂NaBiCl₆双钙钛矿材料具有近红外宽波段发射特性,但低发光效率限制了其在近红外发光领域的应用。本工作通过共沉淀法快速制备微米级尺寸的Cs₂Ag_0.1Na₍0.9_Bi Cl₆:Tm³⁺双钙钛矿晶体,实现了近红外荧光增强,并系统研究了其光学吸收、光致发射(PL)、光致激发(PLE)、时间分辨光致发光和荧光量子效率(PLQY)等光学性能。共沉淀法制备的Cs₂Ag_0.1Na_0.9BiCl₆:Tm³⁺的光学带隙为3.06e V。在350nm紫外光激发下,可以观察到峰值位于680 nm的近红外宽峰发射,这源于自陷激子发光。通过引入Tm³⁺作为新的发光中心,实现了810nm波段的近红外发光增强,在780～830 nm波段荧光量子效率(PLQY)从1.67%提高到11.77%,提高...     

Ce~(3+),Eu~(3+)共掺Lu_3Al_5O_(12)多晶的发光特性及能量传递研究

利用高温固相反应制备了Ce3+、Eu3+共掺杂的(Ce0.01EuxLu0.99-x)3Al5O12(x=0.02%、0.5%、1%、2%)多晶粉末,并对其结构和光谱学特性,特别是Ce3+向Eu3+的能量传递问题进行了研究。X射线衍射结果显示,所制备样品具有单一的石榴石结构。利用X射线激发发射谱和光致激发发射谱研究了Eu3+掺入浓度对发光中心Ce3+和Eu3+离子发光特性的影响以及Ce3+向Eu3+的能量传递。样品的热释光谱进一步证明Ce3+向Eu3+的能量传递及其与Eu3+浓度之间的变化关系。     

红色荧光粉Zr(MoO4)2· MoO3∶Eu3+的发光性能和能量转移

采用共沉淀法制备了一系列Zr(MoO_4)_2·MoO_3∶Eu~(3+),并对荧光粉进行了X射线衍射仪和荧光光谱仪分析。结果表明:荧光粉为一混晶,由Zr(MoO4)2和MoO3组成。荧光粉在465nm的激发下,在617nm处产生强的红光发射,发射光谱在617nm处的强度是激发光谱在465nm处强度的2.26倍。这是因为在465nm的激发下,Eu3+的能量从磁偶极中心转移到电偶极中心,使617nm处发光增强。对蓝光激发白光LED而言,Zr(MoO4)2·MoO3∶Eu3+是具有一定应用前景的红色荧光粉。     

共沉淀法合成CaO:Eu~(3+)红色荧光粉的研究

采用共沉淀法合成CaO:Eu3+红色荧光粉,探讨了Eu3+离子的掺杂量、煅烧温度和煅烧时间对样品发光性能的影响,并利用X-射线衍射仪(XRD)、扫描电镜(SEM)和荧光光度仪(PL-PLE)等仪器对样品的性能进行表征.结果表明:掺杂Eu3+作为发光中心进入到CaO基质的晶格中,其最佳掺杂量为1.5%(摩尔含量);最佳煅烧温度和煅烧时间分别为1100℃和4h,样品的激发峰位于200~290nm之间,对应于Eu3+-O2-的电荷迁移跃迁(CTB),属于宽带激发;Eu3+离子主要占据严格对称的格位,其最大发射峰位于592nm,对应于5D0→7F1磁偶极跃迁,属于红色发光.     

硼酸对纳米BaMgAl10O17:Eu2+发光材料制备、晶体结构及其发光性能的影响

用燃烧法合成了由Eu2 离子激活的BaMgAl10O17:Eu2 蓝色荧光粉,着重研究了助熔剂H3BO3对荧光材料的晶体结构及发光性能的影响.结果表明,添加助熔剂有利于荧光粉的晶化,并增强荧光粉的激发和发射光谱强度;H3BO3的最佳添加量为1.0%,可使BaMgAl10O17:Eu2 的发光强度提高30%以上.     

高温固相法制备CaCO_3:Eu~(3+),Li~+红色荧光粉

以CaCO3、Eu2O3和Li2CO3为主要原料,采用高温固相法,首次制备CaCO3:Eu3+,Li+红色荧光粉。通过对前驱物进行同步差热分析(TG-SDTA),确定其煅烧温度;利用X射线衍射(XRD)、傅立叶变换红外光谱(FT-IR)和拉曼光谱对样品的结构进行表征;采用荧光光度仪对样品的发光性能进行测试。结果表明:前驱物的煅烧温度为655℃时,样品主晶相为方解石型CaCO3,掺杂Eu3+和Li+离子分别作为发光中心和敏化剂进入到CaCO3的晶格中。荧光粉的最大激发峰位于272nm,属于紫外激发,最大发射峰位于608nm附近,对应于Eu3+离子的5d0→7f2跃迁,并且Eu3+离子在CaCO3基质中处于偏离或无反演对称中心的格位上。     

Photostriction of CH3NH3PbBr3 Perovskite Crystals

Organic–inorganic hybrid perovskite materials exhibit a variety of physical properties. Pronounced coupling between phonon, organic cations, and the inorganic framework suggest that these materials exhibit strong light–matter interactions. The photoinduced strain of CH₃NH₃PbBr₃ is investigated using high‐resolution and contactless in situ Raman spectroscopy. Under illumination, the material exhibits large blue shifts in its Raman spectra that indicate significant structural deformations (i.e., photostriction). From these shifts, the photostrictive coefficient of CH₃NH₃PbBr₃ is calculated as 2.08 × 10^?8 m² W^?1 at room temperature under visible light illumination. The significant photostriction of CH₃NH₃PbBr₃ is attributed to a combination of the photovoltaic effect and translational symmetry loss of the molecular configuration via strong translation–rotation coupling. Unlike CH₃NH₃PbI₃, it is noted that the photostriction of CH₃NH₃PbBr₃ is extremely stable, demonstrating no signs of optical decay for at least 30 d. These results suggest the potential of CH₃NH₃PbBr₃ for applications in next‐generation optical micro‐electromechanical devices.     

(La2/3Ca1/3)(Mn(3-x)/3)Fex/3)O3体系磁电阻行为的研究

通过系统地测量（La_2/3Ca_1/3）（Mn_{（3-x）／3}Fe_x／3）O₃（x＝0、0.1、0．2、0．3的体系样品的电阻率-温度关系以及一定温度下磁电阻率与磁场的关系,发现随x的变化其磁电阻率峰和电阻率峰均发生位移,磁电阻率峰值增大,并伴生磁电阻率峰展宽效应．作者认为由于Fe的替代,引起体系中Mn³⁺／Mn⁴⁺比率及磁矩的变化,加之外场对磁有序结构的调制作用,从而影响了Mn³⁺－O^－Mn⁴⁺的双交换作用,最终导致磁电阻行为发生变化．     

Constitution of the Ni3Cr-Ni3Al-Ni3W system

Isothermal sections of the Ni-Cr-Al-W system have been investigated at 75 at % Ni and temperatures of 1523 and 1273 K, by means of phase compositional analysis, X-ray diffraction and microscopical examination. The alloys studied lay in the range 2.5 to 10 at % Cr, 12.5 to 20 at% Al, 2.5 to 6.25 at % W, The phases formed were, and the bcc solid solution based on tungsten (designated ₂). The maximum extent of the region was found to be 3 at % each of chromium and tungsten. Preferential partitioning of tungsten to occurred. Study of an Ni-10Cr-12.5Al-2.5W alloy aged at 1273 and 1073 K, after quenching from 1573 K, showed that changes in and compositions and lattice parameters occur as a function of ageing time.     

PbZrO3-CdTiO3 solid solutions

The structural, nonlinear optical, and dielectric properties of (1-x)PbZrO₃ ·xtCdTiO₃ solid solutions were studied. The phase relations in the composition rangesx = 0–0.3 and 0.85-1.0 were established. The results suggest that the ferrielectric ordering in CdTiO₃ persists up to 730 K.     

Phase equilibria in the system LaMnO3 + δ-SrMnO3-LaFeO3-SrFeO3 − d

We have revealed the formation of a continuous series of orthorhombic LaMn_{1 ? y} Fe_yO₃ solid solutions (0<y<1); La_{1 ? x} Sr_xFeO₃ solid solutions in the composition range 0 < x ≤ 0.8, with an orthorhombic structure at 0 < x ≤ 0.6 and a cubic structure at 0.6 < x ≤ 0.8; and a tetragonal SrMn_{1 ? y} Fe_yO₃ phase in the range 0.6 ≤ y ≤ 1. The composition stability limits of the perovskite phase La_{1 ? x} Sr_xMn_{1 ? y} Fe_yO₃ have been determined, and the 1100°C isotherm of the La₂O₃-SrO-Mn₃O₄-Fe₂O₃ system in air has been constructed.     

Multicolor up-conversion emissions of Tm3+/Er3+/Yb3+ tri-doped YF3 phosphors

Tm3+/Er3+/Yb3+ tri-doped yttrium fluoride (YF3) phosphors were prepared by a facile hydrothermal method. X-ray topographic analysis found that the phosphors were crystallized products. Their sizes and morphologies were characterized by scanning electron microscopy (SEM, Hitachi S-4800), which indicated that most of the YF3 phosphors were hundreds of nanometers in size. Up-conversion (UC) spectra were recorded under 980-nm diode laser excitation at room temperature with a fluorescence spectrometer (Hitachi F-4500). Plenty of UC emissions of Tm3+ and Er3+ were observed from ultraviolet to red. For Tm3+ ions, a five-photon process (approximately 291 nm and approximately 347 nm), a four-photon process (approximately 362 nm and approximately 452 nm), and a three-photon process (approximately 475 nm) were identified in the UC spectra. The UC emissions from the Er3+ were: approximately 380 nm, approximately 408 nm, approximately 521 nm, approximately 537 nm, and approximately 652 nm. Therefore, cyan-white light can be observed by the naked eye at 980-nm excitation, even under low excitation power density. By comparing the UC spectra of the phosphors annealed at different temperatures, we found that the intensity of the UC luminescence increased as annealing temperature increased. Furthermore, the spectral dependencies on Tm3+ doped concentrations were studied. The energy transfer processes and fluorescence dynamics in the tri-doped system are currently being investigated.     

3 Cr3 Mo3 VNb 在热冲孔中的应用研究

高合金钢热冲孔冲头寿命关系到模具与产品成本、生产效率、自动化设备的使用,因此,应注重冲头的选材、材料制备与冲头制造工艺。 用 3 Cr3Mo3 VNb 作为高合金钢热冲孔冲头,为提高模具寿命,在材料制备上,优化了成分,采用电渣重熔冶炼,减少杂质,毛坯锻造两次,用大锻造比锻造,冲头热处理用真空炉,三次回火,热处理硬度取 HRC42 ~ 46 ,冲头表面处理采用镀铬工艺,开展了热冲孔工艺试验。 结果表明,用3 Cr3Mo3 VNb 可使冲孔冲头寿命平均达到 800 件以上。     

Processing and properties of Pb(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3 ceramic relaxors

The shrinkage phenomenon during the reaction-sintering of PMN-PZT from low-temperature pre-reacted 3PbO + MgNb₂O₆ + PZT powder mixtures has been studied. It was assumed that the pre-reaction treatment leads to the formation of a pyrochlore phase containing very active MgO small particles, and that the strong shrinkage occurring up to 800 °C took place by the diffusion of Mg²⁺ cations into the pyrochlore phase particles, thus controlling the reaction-sintering shrinkage phenomenon. Above that temperature the densification was enhanced by a liquid-phase sintering process. The ceramics sintered at 1050 °C for 2 h showed 96% of the theoretical density, and the dielectric constant of such a sintered ceramic showed a maximum value of 17 000 at 1 kHz. It was also found that the dielectric constant decreased with increasing grain size. Although the role of PZT in enhancing the dielectric constant of otherwise low-purity PMN ceramics is not clear, the increase in K is assumed to be a solid-solution effect. The presence of impurities and the PbO stoichiometry could be influencing the not too high dielectric constant value of PMN-PZT ceramics.