Efficient Near-infrared Down-conversion Phosphor of Ce~(3+)/Yb~(3+) Co-doped La_3Ga_5SiO_(14) and Its Spectral Structural Modulation

A series of near-infrared(NIR) down-conversion phosphors of La_3 Ga_5 SiO_(14)(LGS):Ce~(3+)/Yb~(3+)were synthesized via high-temperature solid-state reaction. Under excitation at 345 nm, the phosphors show strong NIR emission around 978 nm, which matches well with the optimal spectral response of crystalline silicon(c-Si)solar cells. The emission spectra and decay curves were used to demonstrate the energy transfer from Ce~(3+) to Yb~(3+).The energy transfer mechanism was discussed in detail, indicating that the energy transfer from Ce~(3+) to Yb3+ is dominated by a single photon process, and the energy transfer efficiency is up to 51%. In addition, La3 Ga5-zAlzSiO_(14)(z = 0, 1, 2, 3):Ce3+/Yb~(3+) were also synthesized. The NIR emission intensity of La3 Ga2 Al3 SiO14:1%Ce~(3+)/5%Yb~(3+) is 4.6 times that of LGS:1%Ce~(3+)/5%Yb~(3+), and the thermal relaxation was used to explain this phenomenon. The results show that La_3 Ga_(5-z)AlzSiO_(14)(z = 0, 1, 2, 3):1%Ce~(3+)/5%Yb~(3+) phosphors have the potential to increase the conversion efficiency of c-Si solar cells.     

Synthesis and visible-light-induced sacrificial photocatalytic water oxidation of quinary oxynitride BaNb_(0.5)Ta_(0.5)O_2N crystals

Quinary oxynitride BaNb_(0.5)Ta_(0.5)O_2N crystals were fabricated through the partial nitridation and acidification of the KCl flux grown Ba_5Nb_2Ta_2O_(15)crystals.The parameters of both the solute concentrations and cooling rates are optimized for the KCl flux growth of the larger Ba_5Nb_2Ta_2O_(15)crystals with clearer crystal habits.Here,the optimal Ba_5Nb_2Ta_2O_(15)crystals mainly have a hexagonal plate-like shape.After the partial nitridation and acidification,the porous Ba Nb_(0.5)Ta_(0.5)O_2N crystals maintained the crystal shape of the oxide precursor and had a single-crystalline nature.For the Ba_5Nb_2Ta_2O_(15)crystals,the wavelength of the absorption edge was about 707 nm.Especially,the CoO_x-loaded Ba Nb_(0.5)Ta_(0.5)O_2N photocatalyst demonstrated the comparatively high amount of O_2gas(150.7μmol)during the 5 h visible-light-induced sacrificial water oxidation half-reaction,which might be achieved due to the high crystallinity and visible-light absorption property.     

La_(0.5)Na_(0.5)TiO_3纳米晶的制备及光致发光研究

以硬脂酸、硝酸镧、氢氧化钠和钛酸四丁酯为原料制备了La0 .5Na0 .5TiO3 纳米晶 ,粒度最小可达 1 4nm ,烧成温度为 50 0℃ ,低于传统固相反应的合成温度。光致发光研究表明 :用 392nm光作激发光 ,在室温下观察到了一个强的蓝光发射带 ,并且它的强度和半宽度随粒度发生明显变化。     

Molecular dynamics simulations of La_2O_3 thin films on SiO_2

Classical molecular dynamics is used to investigate the equilibrium state of the surface region and interface of heteroepitaxial La_2O_3 thin films.Due to the lattice mismatch,heteroepitaxial thin films are subject to very large stress.For this reason the behavior of La_2O_3 thin films at SiO_2interface becomes an important concern.Our result indicates that La_2O_3 can uniformly wet SiO_2 surface.The properties of the simulated films are analyzed and the lack of any discernible crystalline phase in epitaxial La_2O_3 on SiO_2 indicates that the lattice mismatch between SiO_2 and La_2O_3 is sufficiently large to prevent the formation of even short-range orders in La_2O_3 film.     

Ce0.5+xZr0.4-xLa0.1O2-Al2O3催化剂催化燃烧柴油车碳烟

采用共沉淀法制备了系列Ce_0.5+xZr_0.4-xLa_0.1O₂-Al₂O₃催化剂, 其中0≤x≤0.4且Ce_0.5+xZr_0.4-xLa_0.1O₂与Al₂O₃的质量比为1:1. 考察了该系列催化剂对柴油车排放碳烟的催化燃烧性能, 并用低温N2吸附-脱附、X射线衍射(XRD)、X射线光电子能谱(XPS)、氢气程序升温还原(H₂-TPR)和氧气程序升温脱附(O₂-TPD)等手段对催化剂进行了表征. 研究结果表明该系列催化剂均形成了具有立方萤石结构的固溶体. 当x=0.2时, Ce³⁺离子在催化剂表面有一定的富集, 此时催化剂具有最大的β氧脱附峰和最好的表面还原性能, 同时具有良好的催化碳烟氧化活性, 碳烟在该催化剂的起燃温度为360 °C, 具有较好的应用前景.     

Spectroscopy and Energy Transfer in Yb3＋ and Tm3＋ Co-doped Gd3Ga5O12 Crystal

Yb3+/Tm3+ co-doped Gd3Ga5O12 single crystal with a dimension of Φ30mm×20mm was grown successfully by Czochralski method.The absorption spectrum was recorded at room temperature and used to calculate the absorption cross-section.Based on the Judd-Ofelt(J-O) theory,we obtained the three intensity parameters and spectral parameters of this crystal,such as the line strengths,oscillator strengths,radiative probabilities and radiative lifetimes as well as the fluorescent branching ratios.Room temperature fluorescence spectra and luminescence decay curves were recorded.The energy transfer between Yb3+-Tm3+ was observed and the mechanism was discussed.The stimulated emission cross-section of the 3F4→3H6 transition was calculated by the Füchtbauer-Ladenburg(F-L) equation.The potential laser gains for this transition were also investigated.This crystal is promising as a tunable infrared laser crystal at 2.0 μm.     

稀土取代的复合氧化物Eu_（0．5）RE_（0．5）Fe_（0．5）Mn_（0．

利用固相反应合成了稀土取代的复合氧化物Ｅｕ_（０．５）ＲＥ_（０．５）Ｆｅ_（０．５）Ｍｎ_（０．５）Ｏ_３（ＲＥ＝Ｌａ，Ｐｒ，Ｎｄ，Ｓｍ，Ｇｄ，Ｔｂ，Ｄｙ，Ｈｏ，Ｅｒ，Ｔｍ，Ｙｂ）．测量了这些化合物的ＸＲＤ和ＸＰＳ谱。在ＸＰＳ研究中发现，稀土取代而使稀土元素本身的结合能相对于其倍半氧化物中的有所降低；在取代的复合氧化物中，随着ＲＥ离子半径的减小，Ｆｅ、Ｍｎ的结合能随之增加。     

一种新型氧离子导体：La3GaMo2O12

A new oxide ion conductor,La_3GaMo_2O_(12),with a bulk conductivity of 2.7×10~(-2)S·cm~(-1) at 800 ℃ in air at-mosphere was prepared by the traditional solid-state reaction.The room temperature X-ray diffraction data could beindexed on a monoclinic cell with lattice parameters of a=0.5602(2) nm,b=0.3224(1) nm,c=1.5741(1) nm,β=102.555(0)°,V= 0.2775(2) nm~3 and space group Pc(7).Ac impedance measurements in various atmospheres furthersupport that it is an oxide ion conductor.This material was stable in various atmospheres with oxygen partial pres-sure p(O_2)ranging from 1.0×10~5 to 1.0×10~(-7) Pa at 800 ℃.A reversible polymorphic phase transition occurred atelevated temperatures as confirmed by the differential thermal analysis and dilatometric measurement.     

KTa_(0.5)Nb_(0.5)O_3电子结构的第一性原理研究

用全电势线性缀加平面波法 (FLAPW )计算了KTa0 .5Nb0 .5O3 铁电相和顺电相的态密度、能带结构 .通过对两相态密度的对比分析我们发现在铁电相 ,钽原子的d电子和氧原子的 2p电子以及铌原子d电子与氧原子的 2p电子之间存在强烈的轨道杂化 ,对能带的分析也得出同样的结论 .这种轨道杂化对KTa0 .5Nb0 .5O3 铁电性的稳定有着重要的意义 .钽原子在四方铁电体KTa1 xNbxO3 中的作用与在纯钽酸钾中的作用有明显的差别 .     

KTa_(0.5)Nb_(0.5)O_3电子结构的第一性原理研究

用全电势线性缀加平面波法（FLAPW）计算了KTa_(0.5)Nb_(0.5)O_3铁电相和 顺电相的态密度、能带结构。通过对两相态密度的对比分析我们发现在铁电相，钽 原子的d电子和氧原子的2p电子以及铌原子d电子与氧原子的2p电子之间存在强烈的 轨道杂化，对能带的分析也得出同样的结论。这种轨道杂化对KTa_(0.5)Nb_(0.5) O_3铁电性的稳定有着重要的意义。钽原子在四方铁电体KTa_(1-x)Nb_xO_3中的作 用与在纯钽酸钾中的作用有明显的差别。     

Ga2O3/HZSM-5催化剂上丙烷脱氢反应

以直接水热合成和低硅沸石高温水蒸气脱铝两种方法制备了不同Si/Al摩尔比的HZSM-5载体, 考察了Ga₂O₃/HZSM-5催化剂上丙烷脱氢制丙烯的反应性能. 结合XRD, N₂气吸附, ²⁷Al MAS NMR和NH₃-TPD等表征方法, 讨论了催化剂酸性质和孔性质与性能的关系. 实验结果表明, 减少催化剂表面的中强酸量可以显著提高反应的稳定性和丙烯的选择性; 水蒸气脱铝所增加的介孔有同样的效果, 这可能是由于介孔的存在有利于丙烯的脱附和扩散而抑制了寡聚、环化等副反应的发生, 减少了表面积炭的可能性.     

La_2CaB_(10)O_(19):Ce~(3+)在VUV-Vis范围的发光性质研究

通过研究La_2CaB_(10)O_(19):Ce~(3+)在VUV-Vis范围的光谱.发现Ce~(3+)在La_2CaB_(10)O-(19)中共有两种格位.分别取代了十配位的I。a’“和八配位的Ca”,从而发射光谱中没有出现特征的双峰,而出现了峰值约位于307,330和 356 nm的3个发射峰.由于在低对称性晶体场中d轨道的分裂.激发光谱中位于194.224,243.260,274和318 nm的峰是由两个格位的Ce~(3+)的f-d跃迁引起的.Ce~(3+)占据两个格位,可以通过以Eu~(3+)为荧光探针的发射光谱中出现的两个~5D_(0-)~7F_0跃迁得到验证.峰值位于162 nm的激发谱带是基质吸收带.与基质禁带宽度相对应.通过计算,不排除其中包含O~(2-)→Ce~(3+)的电荷迁移带的可能性.     

EuP5O14的配位场理论计算

ＥｕＰ_５Ｏ_（１４）的配位场理论计算　　范英芳，杨频，潘大丰（山西大学分子科学研究所，山西省农业科学院情报所，太原，０３０００６）关键词配位场理论，Ｃ_（２ｖ）对称场，稀土配合物，ＥｕＰ_５Ｏ_（１４）ＥｕＰ５Ｏ１４是七十年代发现的一种新型发光材料，它...     

A Study on Production of Carbon Nanotubes by CH_4 Decomposition over LaNiO_3,La_4Ni_3O_(10),La_3Ni_2O_7 and La_2NiO_4

IntroductionIn the present study, by employing the citric acid complex method1, we prepared a series of perovskite-type oxides, viz. LaNiO3, La4Ni3O10, La3Ni2O7 and La2NiO4 for the growth of CNTs. After H2 reduction, the catalysts turn into La2O3 and active component Ni0 of various sizes. By means of CH4 decomposition over the reduced catalysts, high quality CNTs with dissimilar diameters can be generated in mass amount. In this paper, we attempt to make a comparison on the structure…     

3D Raman Spectroscopy of Large Zeolite ZSM-5 Crystals

Hydrothermal treatment is a common method used to modify the physicochemical properties of zeolite-based catalyst materials. It alters the number and type of acid sites through dealumination and increases molecular diffusion by mesopore formation. Steaming also reduces the structural integrity of zeolite frameworks. In this study, Raman microscopy has been used to map large zeolite ZSM-5 crystals before and after steaming. 3D elemental maps of T−O (T: Al or Si) sites of the zeolite were obtained. The Raman active vibrational bands were determined, which are indicative of (non-) framework Al, as well as of structural integrity. Zeolite steaming caused the introduction of additional heterogeneities within the zeolite framework. Al migration and the formation of extra-framework Al species were observed. The described experiments demonstrate the capability of 3D Raman spectroscopy as a valuable tool to obtain information on the spatial distributions of framework elements as well as defects within a zeolite-based material.     

Studies on Kinetic Properties of Active Oxygen on the Surfaces of V_2O_5/SiO_2, V_2O_5-MoO_3/SiO_2 and V_2O5-P_2O5/SiO_2 Catalysts

Applying the TPD-MS with a high sensitivity of determination, the TPD spectrum of surface oxygen of V2O5/SiO2, V2O5-MoO3/SiO2 and V2O6-P2O5/SiO2 catalysts was obtained. The surface oxygen of these catalysts can be divided into three groups according to the desorption temperature. O2- desorbs mainly from 373K. to 423K, O- from 673K to 873K and O2- at above 873K. The activation energy and frequency factor of all the three kinds of oxygen species were calculated. Based on these results, the mechanism of oxygen desorption and the influence of P2O5 and MoO3 on the properties of oxygen supply of V2O5/SiO2 catalst were investigated. MoO3 and a small amount of P2Os increase the number of supplying oxygen and increase the activity of O- species. A large amount of P2O5 increases the number of supplying oxygen and restrains the activity of O- species.     

Nd3+:NaLa(WO4)2晶体的生长和光学性质

Nd3+:NaLa(WO4)2 crystals with a dimension up to 7 mm were grown from a high temperature solution using a double-crucible method. Scanning electron microscopy observations of the crystals showed that there were no small cracks on the surface of the crystals although they underwent two phase transitions when cooling down from high temperatures. X-ray diffraction studies indicated that the as-obtained product is pure low- temperature tetragonal Nd3+:NaLa(WO4)2. The absorption and fluorescence spectra for Nd3+:NaLa(WO4)2 were measured at room temperature. The absorption band at 804 nm has a wide full-width half maximum of 23 nm whose origin is discussed. The absorption and emission cross sections were calculated to be 7.24*10-20 cm2 at 804 nm and 6.54*10-20 cm2 at 1057 nm, respectively.     

C62O3的结构和光谱的理论研究

用ＩＮＤＯ法研究了Ｃ６２Ｏ３的结构与光谱，结果表明，Ｃ６２Ｏ３有Ｃ２０和Ｃ５两种种稳定构型，其中Ｃ２０构型能量较低。利用Ｃ６０的碎片拓扑图讨论基加成及环加成产物对称性的规律，理论计算与＾１３ＣＮＭＲ谱的实验结果相符合。     

Raman and infrared studies of NaLa(MoO4)2:Nd3+

The polarized Raman and i.r. (powder) spectra of 0.5 mole % neodymium doped NaLa(MoO₄)₂ have been analysed on the basis of C_4h crystal symmetry. Group theoretically predicted fundamentals have been observed. The frequencies and intensities are not altered due to doping.