高密度发光材料γ-Bi2WO6:Pr3+的发光性质研究

研究了用固相法制备的高密度发光材料γ-Bi2WO6Pr3+的结构、光致发光光谱、激发谱和γ-Bi2WO6的漫反射谱.由实验测得它的晶格参数为a=5.45A,b=16.42A,c=5.43A,密度Dx=9.53g/cm3.它的光致发光光谱主发射峰位于600、608、611、629nm,分别来自于pr3+的1D2→3H4、3P0→3H5、3P0→3H6、3P0→3F2跃迁的发射.其激发谱由位于约225～430nm范围内、最大值约在372nm的主激发带和450nm的激发峰组成;主激发带来自于基质,可能是基质的带间吸收、W-O间电荷迁移吸收和缺陷能级的吸收;450nm的激发峰来自于pr3+的3H4→3P2跃迁吸收.BWOPr3+的最佳掺杂浓度为0.8mol%左右.     

Ca_2SiO_3Cl_2∶Eu~(3+)材料的发光特性

采用高温固相法合成了Ca2SiO3Cl2∶Eu3+红色发光材料。利用X射线分析了材料的晶体结构,其为四方晶系;在400nm近紫外光激发下,材料呈红色发射,主发射峰位于582、599、623、655和691nm,分别对应Eu3+的5D0→7F0、7F1、7F2、7F3和7F4特征跃迁;监测599nm最强发射峰,激发光谱覆盖200～450nm,主激发峰位于400nm。研究了Eu3+摩尔浓度对Ca2SiO3Cl2∶Eu3+材料发射强度的影响,结果显示,随Eu3+浓度的增大,强度先增大、后减小,Eu3+浓度为1%时,强度最大。引入Li+后,材料的发射强度进一步增大。     

溶胶-凝胶法合成Sr2SiO4:Sm3+及其发光性能

采用溶胶-凝胶法合成了Sr<,2>SiO<,4>:Sm<,3+>红色荧光粉,用XRD、SEM、PL对样品进行了结构、型貌及发光性能表征.结果表明,所得样品为单斜晶系结构,呈粒径为0.1～0.3μm、1μm左右长的纤维状小颗粒;在波长402nm的紫外激发下,样品发射光谱由位于红橙区的3个主要荧光发射峰组成,峰值分别位于568,605nm和651nm,对应了Sm<'3+>的<'4>G<,5/2>→<'6>H<,5/2>,<'4>G<,5/2>→<'6>H<,7/2>和<'4>G<,5/2>→<'6>H<,9/2>特征跃迁发射,605nm的发射最强,是一种适用于白光LED的红色荧光粉.     

980nm LD激发下Tm3+和Yb3+共掺杂的PGETYA玻璃上转换发光的研究

制备了一种Tm3+和Yb3+共掺杂的PGETYA氟氧玻璃材料,其组分为61.97PbF2-30.98GeO2-3Al2O3-0.05Tm2O3-4Yb2O3.测量了该玻璃系统在980nmLD激发下的上转换发光光谱,观察到很强的476nm的蓝色荧光,它来源于1G4→3H6的跃迁.同时,还有两个较弱的红色荧光来源于1G4→3H4和3F3→3H6的跃迁.测量并讨论了蓝色和红色上转换荧光强度与LD工作电流的关系.     

Pr掺杂SrBi_2Ta_2O_9多功能铁电体的光致发光研究(英文)

本文报道了Pr掺杂SrBi2Ta2O9(SBTO)铋层状铁电材料的光致发光特性。通过适量的Pr掺杂制得的SrBi2Ta2O9陶瓷样品在室温下具有很强的红光和绿光发射。光致发光激发谱显示样品具有蓝光激发特性,该激发带对应Pr3+离子的基态3H4到激发态3PJ(J=0,1,2)的跃迁吸收。在蓝光激发下,样品具有宽带发射,发射峰对应Pr3+离子f-f辐射跃迁中:3P1→3H5(532 nm),3P0→3H5(546 nm),1D2→3H4(600 nm),3P0→3H6(620 nm),3P0→3F2(656 nm)和3P0→3F4(743 nm)跃迁。Pr掺杂SBTO样品蓝光激发的光致发光特性将可能使其在白光LED及其相关器件中得到应用。     

溶胶-凝胶燃烧法制备YAG:Sm粉体及其性能

采用溶胶-凝胶燃烧法制备出掺钐钇铝石榴石(YAG:Sm)荧光粉,并研究了凝胶化加热温度、柠檬酸/硝酸盐比值(MRCM)、pH值等因素对前驱体和YAG粉体性能的影响。结果表明:当加热温度为80℃,MRCM=1~2,pH值在1~3时,凝胶化时间较短,胶体成型情况良好;随着热处理温度的升高,前驱体从金属羧酸盐变成无定形碳酸盐,至900℃转变为纯YAG相。Sm3+:YAG在550~750nm波段内的发射峰对应于Sm3+的4G5/2→6HJ(J=5/2,7/2,9/2和11/2)能级跃迁,其中对应4G5/2→6H7/2跃迁的发射峰强度最大。     

Ca2SiO3Cl2∶Dy3+单一基质白光荧光粉的制备及发光特性

采用溶胶-凝胶法合成了发射白光的Ca2SiO3Cl2∶Dy3+荧光粉。利用XRD分析了荧光粉的晶体结构,其为四方晶系。在350nm近紫外光激发下,荧光粉呈白光发射,有两个主发射峰位分别于482和573nm,分别对应于Dy3+的4F9/2→6H15/2和4F9/2→6H13/2跃迁;监测573nm最强发射峰,激发光谱覆盖200～450nm,主激发峰位于350nm。研究结果表明保温时间的延长有利于发射强度的提高,伴随着Dy3+浓度的增大,发射光谱图中的两个主发射峰先增强后减弱,Dy3+的最佳浓度为2%(摩尔分数)。     

Sm3+/Ce3+/Tb3+共掺CaO-B2O3-SiO2发光玻璃的制备及发光性能研究

采用高温熔融法制备了Sm3+/Ce3+/Tb3+共掺杂的CaO-B2O3-SiO2发光玻璃材料,并用荧光分光光度计和CIE色度坐标对其发光性能进行了研究。发射光谱表明,在374nm激发下,Sm3+/Ce3+/Tb3+共掺杂CaO-B2O3-SiO2发光玻璃的发射光谱中同时观测到了红橙光、蓝光和绿光的发射带,这些发射带的混合实现了白光发射。此外,在Sm2O3和Tb4O7含量不变的情况下,随着CeO2含量的减小,Sm3+/Ce3+/Tb3+共掺杂发光玻璃的发光颜色在白光区逐渐由蓝光区附近过渡到黄光区附近。     

20GaF3-15InF3-20CdF2-15ZnF2-18PbF2-10SnF2-2TmF3玻璃光谱性质研究

制备了掺Tm^3 离子GICZPS玻璃：20GaF3-15InF3-20CdF2-15ZnF2-18PbF2-10SnF2-2TmF3，用Judd-Ofelt理论计算了玻璃的光学参数，研究了玻璃的发光性质，并探讨了其发光机理．结果表明，在641nm激发下，可以观察到485nm(^1G4→^3H6)和528nm(^1G2→^3H5)两个上转换荧光发射峰。     

Gd_2O_2SO_4∶Dy~(3+)纳米粉体的共沉淀法合成及光致发光研究

采用Gd2O3、Dy2O3、H2SO4和NaOH为实验原料,通过共沉淀法合成了Gd2O2SO4∶Dy3+纳米粉体。利用X射线衍射(XRD)、透射电子显微镜(TEM)和光致发光(PL)光谱等手段对合成的粉体进行了表征。XRD分析表明前躯体在空气气氛下900℃煅烧2h能转化成纯相的Gd2O2SO4∶Dy3+。TEM观察显示Gd2O2SO4∶Dy3+粉体形貌为近球形,分散性良好,粒度大小为20～40nm。PL光谱分析表明在277nm紫外光激发下,Gd2O2SO4∶Dy3+的主次发射峰分别位于575nm(黄光)和485nm(蓝光),分别归属于Dy3+的4F9/2→6H13/2和4F9/2→6H15/2跃迁。Dy3+的猝灭浓度是2%(摩尔分数),猝灭机理是由于Dy3+和Dy3+之间的交换相互作用。余辉光谱研究表明Dy3+的4F9/2→6H13/2和4F9/2→6H15/2跃迁均具有e单指数衰减行为,荧光寿命分别为0.468和0.462ms。     

VLE data for CO2-CF2Cl2, N2-CO2, N2-CF2Cl2 and N2-CO2-CF2Cl

Knowledge about vapour-liquid (VLE) is required as a basis of reliable calculations for separation processes. Correlations available for the prediction of T, p, x, y data are less accurate for mixtures at high pressures and mixtures containing supercritical components. The results of VLE experiments are reported and compared with data calculated with equations of state.     

Preparation of ZrO2-CeO2 and HfO2-CeO2 nanopowders

We prepared weakly agglomerated powders of ZrO₂-CeO₂ and HfO₂-CeO₂ solid solutions 5–8 nm in particle size, consisting of monoclinic and tetragonal phases. After heat treatment at 1200°C, the crystallite size was 30 and 14 nm, respectively. We also examined the effect of precipitate freeze drying on the crystallization of hafnia-based solid solutions containing up to 20 mol % CeO₂.     

Thermal diffusion in binary mixtures H2-CCl2F2 and H2-CHClF2

Thermal diffusion coefficients were measured in two gaseous mixtures, in which one component was close to the critical temperature, in the pressure range (19.6–127.4)·10⁴ N/m² and at a freon concentration of 0.25–0.8.     

Comparison of the Electronic Structures of La2CuO4, Sr2CuO2Cl2, and Sr2CuO2F2

First-principles cluster calculations are reported of the local electronic structure of the three compounds: La₂CuO₄, Sr₂CuO₂Cl₂, and Sr₂CuO₂F₂. The copper ${\text{3d}}_{x^2 - y^2 } $ and the planar oxygen 2p _σ atomic orbitals exhibit a similar degree of covalency. The out-of-plane orbitals, however, are quite different with the ${\text{3}}d_{3z^2 - r^2 } $ atomic orbital lowered significantly in energy for chlorine and fluorine apical positions.     

Radial GRIN glasses in Li2O-Na2O-Al2O3-TiO2-SiO2 systems

A series of GRIN glass rods have been developed in Li2O-Na2O-Al2O3-TiO2-SiO2 systems. Negative radial refractive index profiles were generated by exchanging Na+ for Li+ ions in these glass rods. It has been observed that TiO2 plays a vital role in increase in the profile depth and maximum change in the refractive index because of its ambivalent nature. Change in the refractive index can be further increased by increasing the concentration of exchanging cation in the base glass.     

Elastic and Electronic Properties of Superconducting CaPd 2 As 2 and SrPd 2 As 2 vs. Non-superconducting BaPd 2 As 2

The first-principles calculations were performed to predict the elastic and electronic properties of the superconducting ThCr₂Si₂-type phases CaPd₂As₂ and SrPd₂As₂ in comparison with the non-superconducting CeMg₂Si₂-type phase BaPd₂As₂. Besides, the same properties were compared for CeMg₂Si₂- and ThCr₂Si₂-type polymorphs of BaPd₂As₂. We found that all these phases are mechanically stable and belong to soft materials with low hardness. The near-Fermi region is formed by the valence states of the blocks [Pd₂As₂] with decisive contributions of Pd 4d states. The values of N(E _F) increase in the sequence: CaPd₂As₂ < SrPd₂As₂ < BaPd₂As₂, i.e. in the reverse sequence relative to the transition temperatures T _C. Thus, the change in T _C cannot be explained by the electronic factor, i.e. by the simple correlation T _C～N(E _F). Most likely the decrease in T _C in the sequence CaPd₂As₂ → SrPd₂As₂ and the absence of a superconducting transition in BaPd₂As₂ are related to the structural factors and the peculiarities of the electron–phonon coupling mechanism.     

Si_2N_2O-Al_2O_3-La_2O_3和Si_2N_2O-Al_2O_3-CaO系统的亚固相关系

本文给出了 Si_2N_2O-Al_2O_3-La_2O_3和 Si_2N_2O-Al_2O_3-CaO 系统的亚固相图。实验结果表明:在 Si_2N_2O-Al_2O_3-CaO 系统中有一个未知结构的新化合物 CaO·Si_2N_2O,在3CaO·Si_2N_2O 和3CaO·Al_2O_3两化合物之间形成连续立方固溶体。而 Si_2N_2O-Al_2O_3-La_2O_3系统中则没有发现新化合物。在两个系统的富 Si_2N_2O区,过量的 Si_2N_2O 与 La_2O_3和 CaO 分别反应形成 Si_3N_4与 La_(10)[SiO_4]_(?)N_2(H-相)(和 CaSiO_3。所研究的这两个三元系统中,分别形成了如下几个四元相容性区。在 Si_2N_2O-Al_2O_3-La_2O_3系统内有:H-Si_3N_4-La_2O_3·Si_2N_2O-La_2O_3·Al_2O_3;H-Si_3N_4-La_2O_3·Al_2O_3-La_2O_3·11 Al_2O_3;H-Si_3N_4-La_2O_3·11 Al_2O_3-Al_2O_3;H-Si_3N_4-Al_2O_3-O′s.s;H-Si_3N_4-O′s.s-Si_2N_2O在 Si_2N_2O-Al_2O_3-CaO 系统内有:Si_3N_4-CaSiO_3-CaO·Si_2N_2O-3CaO·Al_2O_3;Si_3N_3-CaSiO_3-3CaO·Al_2O_3-2CaO·Al_2O_3·SiO_(?);Si_(?)N_(?)-CaSiO_3-2CaO·Al_2O_3·SiO_2-Al_2O_3;Si_3N_4-CaSiO_3-Al_2O_(?)-O′s.s;Si_3N_4-CaSiO_3-O′s.s-Si_(?)N_(?)O