La1-xCexCoO3系钙钛矿型催化剂应用于柴油机尾气净化催化性能的研究

采用低温燃烧法制备了Ce4+部分取代La3+的La1-xCexCoO3系钙钛矿型复合氧化物催化剂，用XRD、TGA、SEM和化学分析等方法对催化剂的组成、结构等进行了表征。利用程序升温反应（TPR）技术，对催化剂应用于柴油机常规排放物中的微粒（PM）、碳氢化合物（THC）、氮氧化合物（NOx）的催化脱除性能进行了研究。结果表明，Ce4+部分取代La3+，催化剂表面氧空位浓度增加，同时形成Co3＋-Co2+共存体系，催化剂对THC、NOx催化活性显著提高,且稳定性良好。但Ce4+的掺杂并没有提高催化剂对PM的催化活性。     

高温超导体的Cu-O键型和氧上的部分电荷

多数钙钛矿型化合物是离子型绝缘体，而高温超导化合物则有金属电性，它们是以什么键型为主？对此等人[1]认为用共价或金属成键图像描述高温超导体在化学上更合理，Nepela等人[2]指出超导体临界温度（Tc）随阴离子平均电负性与阳离子平均电负性之差增大而升高．这意味着离子性较强的超导体有较高的人．杨频等问运用晶型键参数方法估算结果表明高温超导体属干部分离子性与部分共价性键．以上不同的结果都是基丁理论处理或估算得到的·本文试图在实验上通过比较不同成键特征的铜化合物的x光电子能潜（＊P8）来估计对高温超导性起重要作用的C…     

铬离子取代对LaGa_（1－x）Cr_xO_3性质的影响

铬离子取代对ＬａＧａ_（１－ｘ）Ｃｒ_ｘＯ_３性质的影响杨健美，苏锵（中国科学院长春应用化学研究所稀土化学与物理开放实验室长春１３００２２）关键词铬离子，取代，ＬａＧａ_（１－ｘ）Ｃｒ_ｘＯ_３，镓酸镧，稀土化合物含过渡元素的ＡＢＯ３型复合氧化物的许多性质...     

改性离子液体中异丁烷与丁烯的烷基化反应

向由无水三氯化铝和盐酸三乙基胺合成的离子液体中溶入不同过渡金属（铜、铁、锌等）离子，考察它们对离子液体催化异丁烷与丁烯烷基化反应性能的影响。结果表明：过渡金属离子的加入能不同程度地影响离子液体的催化性能。溶入Cu2+和Cu+后，离子液体的催化性能有显著的改善，当Cu2+的摩尔加入量为三氯化铝的5%时，烷基化油收率达到丁烯体积的178%，对C8的选择性为75%，烷基化油辛烷值（RON）为92.2，并且离子液体可以重复使用。     

钙钛矿型(La_(0.8)M_(0.2))MnO_3和(La_(0.8)Sr_(0.2))(Mn_(1-x)Fe_x)O_3的XRD和IR光谱的研究

合成了（La0.8M0.2）MnO3（M=Ca2+，Sr2+，Ba2+）和（La0.8Sr0.2）（Mn1-xFex）O3（x=0．1、0．2、0．3、0．4、0．5）两类氧化物，经XRD确认为钙铁矿型氧化物，应用FT－IR对其进行研究，对主要的红外特征振动υ（Mn-O）和δ（O-Mn-O）进行分析表征。这类化合物的υ（Mn-O）和δ（O-Mn-O）的FT－IR特征吸收峰十分相似，但在～608cm－1处出现较大差别，以Sr2+、Ca2+和Ba2+部分A位取代La3+的钙铁矿型氧化物和B位Fe取代Mn时，由于离子的溶解能不同，对晶格的有序排列的影响程度不一，导致了Mn－O键的键力场不同，引起了吸收峰向低波数移动。这种结构上的差异，导致对汽车尾气中的有害成份碳氢化合物（HC）和一氧化碳（CO）的催化氧化能力降低。借此可以用于研究结构与催化性能的关系。     

温度和敏化剂对CaSO4∶ Eu,Ce的光谱性质的影响

采用沉淀法制备了CaSO4Eu, CaSO4Ce, CaSO4 Eu, Ce稀土发光材料, 用荧光光谱仪对发光材料的光谱特性进行了测定. 首次发现并初步讨论了在CaSO4Eu, Ce中存在Ce3+→Eu2+ 的能量传递和Ce3+→Eu3+的电子转移现象. 研究还发现烧结温度和敏化剂的浓度对发光材料的光谱性能影响很大. 单掺Eu的CaSO4Eu体系, 其发光强度随烧结温度增加而增加, 表现为Eu2+的特征发光峰. 烧结温度为400 ℃时, 在CaSO4 Eu, Ce中存在Ce3+→Eu2+ 的能量传递和Ce3+→Eu3+的电子转移. Ce3+浓度较低时, CaSO4Eu,Ce中Eu2+的发光强度随Ce3+离子浓度的增加而增加, Ce3+表现出很好的敏化作用; 当Ce3+离子浓度超过一定范围时, CaSO4Eu,Ce中Ce3+发光强度增大, Eu2+发光强度下降. 当所制备的CaSO4Eu,Ce荧光体烧结温度由400 ℃升至600 ℃时, Ce3+的激发与发射峰基本消失, Eu2+的荧光强度随Ce3+浓度的增加而下降.     

高Tc超导体REBa_2Cu_3O_(7-y)的M-H曲线特性和磁性超导共存

合成出零电阻温度90K左右的高Tc超导体REBa_2Cu_3O_(7-y)(RE=Sm、Eu、Gd、Dy、Ho、Er、Tm),磁性稀土离子对转变温度影响不大,但磁性行为各不相同。在77K测量了它们的磁滞回线,在RE=Gd、Dy、Ho、Er、Tm样品中发现超导和磁性共存现象,这预示着有两种可能的共存方式。实验表明,这些超导体的顺磁性强弱规律与稀土离子在其它晶体中的规律相同,说明超导体的磁性来源于稀土离子。某些样品在低温下表现出反铁磁序,有效玻尔磁子数与三价自由稀土离子值一致。     

呈现强链内铁磁耦合的EO-叠氮与羧基双重桥连一维铜链化合物:合成、晶体结构、磁性及DFT计算

合成了一例以取代苯甲酸衍生物为辅助配体的叠氮铜化合物[Cu（4-Fb）（N₃）（H₂O）]_n （1）（4-Fb=4-formylbenzoate）,并对其结构和磁性进行了表征。单晶结构研究表明,化合物1中的最小不对称单元包含一个晶体学独立的Cu（Ⅱ）离子,中心离子呈现了扭曲的四棱锥几何构型。相邻的Cu（Ⅱ）离子之间通过交替的μ-1,1-（EO）-叠氮和syn,syn-羧酸双重桥连接成一维线性金属链。磁性研究揭示,双重桥的超交换反补偿效应导致目标化合物中链内相邻的Cu（Ⅱ）离子之间表现出强的铁磁耦合作用（J=72.1 cm^-1）。但是并没有观察到铁磁有序和慢磁弛豫现象。作为影响磁性能的重要结构参数,化合物中Cu-N-Cu的角度（113.34°）与已报道的含双重桥的叠氮铜体系相符。对化合物的磁构关系进行了讨论和探究。此外,密度泛函理论（DFT）计算结果为化合物中相邻Cu（Ⅱ）离子间的铁磁耦合作用提供了定性的理论解释。     

一个包含Cu（Ⅱ）和氮氧自由基自旋支链的新颖杂自旋一维链状化合物的结构和磁性研究

本文合成了一个含Cu（Ⅱ）离子和氮氧自由基自旋支链的新颖杂自旋-维链状化合物{[Cu（tcph）（H20）4][cu（tcph）（NIT3Py）2]·2H2O}n（1）（tcph=四氯令K苯二甲酸,NIT3Py=2．（3’-吡啶基）-4,4,5,5-四甲基咪唑啉-3-氧化-1-氧基自由基）．对其结构分析表明,该配合物是一个由四氯邻苯二甲酸连接Cu（Ⅱ）离子构成的一维链状化合物,其中自由基作为自旋支链与水分子分别交替与链上的Cu（Ⅱ）离子进行配位．磁性研究中我们采用了计入自旋态布居的一维链近似模型对其磁性数据进行了合理的拟合,得到以下耦合参数：Jcu2-Rad=22．4cm^-1和J′cul-cu2=-2．4cm^-1,表明分子内Cu2与NIT3Py自由基问存在铁磁相互作用,而由四氯邻苯二甲酸连接的Cu1和Cu2间存在反铁磁作用．     

基于V-型配体的互穿的铜（Ⅱ）配位聚合物的合成、结构、吸附与磁性研究（摘要）

用溶剂热法合成了三个新的CuⅡ配位聚合物[Cu2（oba）2（H2O）（DMF）].3H2O（1）,[Cu4（oba）4（DMF）4].4H2O.DMF（2）和[Cu2（oba）（hmp）2]（3）（其中H2oba=4,4＇-二苯醚二甲酸,Hhmp=2-吡啶甲醇,DMF=N,N′-二甲基甲酰胺）,并通过单晶衍射法等表征它们的结构.化合物1和2均为三重互穿的三维PtS拓扑网络结构,具有一维孔道.化合物3中,2-吡啶甲醇与CuⅡ离子螯合形成Cu4簇单元,Cu4簇单元进一步通过4,4＇-二苯醚二甲酸配体相连形成了具有三维dia拓扑网络的三重互穿结构.化合物2的氮气吸附结果为I型吸附曲线,BET比表面积为562m^2g^-1,Langmuir比表面积为747m^2g^-1.77K和87K时,化合物2的氢气吸附量分别为0.89wt%和0.57wt%.磁性研究表明,化合物3中CuⅡ离子间为铁磁耦合而Cu4簇单元间为弱的反铁磁相互作用.     

Tuning LDA+U for electron localization and structure at oxygen vacancies in ceria

We examine the real space structure and the electronic structure (particularly Ce4f electron localization) of oxygen vacancies in CeO(2) (ceria) as a function of U in density functional theory studies with the rotationally invariant forms of the LDA+U and GGA+U functionals. The four nearest neighbor Ce ions always relax outwards, with those not carrying localized Ce4f charge moving furthest. Several quantification schemes show that the charge starts to become localized at U approximately 3 eV and that the degree of localization reaches a maximum at approximately 6 eV for LDA+U or at approximately 5.5 eV for GGA+U. For higher U it decreases rapidly as charge is transferred onto second neighbor O ions and beyond. The localization is never into atomic corelike states; at maximum localization about 80-90% of the Ce4f charge is located on the two nearest neighboring Ce ions. However, if we look at the total atomic charge we find that the two ions only make a net gain of (0.2-0.4)e each, so localization is actually very incomplete, with localization of Ce4f electrons coming at the expense of moving other electrons off the Ce ions. We have also revisited some properties of defect-free ceria and find that with LDA+U the crystal structure is actually best described with U=3-4 eV, while the experimental band structure is obtained with U=7-8 eV. (For GGA+U the lattice parameters worsen for U>0 eV, but the band structure is similar to LDA+U.) The best overall choice is U approximately 6 eV with LDA+U and approximately 5.5 eV for GGA+U, since the localization is most important, but a consistent choice for both CeO(2) and Ce(2)O(3), with and without vacancies, is hard to find.     

FTIR study of cerium doped electron superconductors R(1.85)Ce(0.15)CuO(4) (R=Nd, Pr, Sm, Eu and Gd)

Systematic FTIR study of electron doped compounds of the T'-series are presented in this paper. Spectroscopic techniques are more sensitive than any other technique to the disorder due to doping in the structure. Polycrystalline 'as prepared' bulk samples, allows one to observe c-axis vibrations clearly, avoiding in-plane (a-b) polarizability due to charge carriers. Even though all R(2)CuO(4)(R=Nd, Pr, Sm, Eu and Gd) doped compounds belong to T' structure, due to the different sizes of the rare earth ionic radii, the structure stabilization is very difficult to achieve since copper-oxygen distance vary from compound to compound and hence the phonon characteristic spectrum of the series. The role of apical oxygen in T-structure is discussed in detail from the point of factor group analysis and compared with the V-structure. The IR study of R(2)CuO(4) (214) compound with Ce doping reveals the difference and similarities of the electronic properties between hole doping and electron doping when compared with T-structure compounds.     

Spin reorientation in the square-lattice antiferromagnets RMnAsO (R = Ce, Nd): density functional analysis of the spin-exchange interactions between the rare-earth and transition-metal ions

The spin reorientation (SR) phenomenon of the square-lattice antiferromagnets RMnAsO (R = Ce, Nd) was investigated by analyzing the spin-exchange interactions between the rare-earth and the transition-metal ions (R(3+) and Mn(2+), respectively) on the basis of density functional calculations. It is found that the symmetry and strength of the Dzyaloshinskii-Moriya (DM) interaction are determined primarily by the partially filled 4f states of the R(3+) ions and that the DM and biquadratic (BQ) exchanges between the R(3+) and the Mn(2+) ions are unusually strong and control the observed spin reorientation phenomenon. Below their SR temperature, the Mn(2+) and Ce(3+) moments are orthogonal in CeMnAsO but are collinear in NdMnAsO, because the DM interaction dominates over the BQ interaction for CeMnAsO, while the opposite is the case for NdMnAsO. Experiments designed to test the implications of our findings are proposed.     

Coordination chemistry of trivalent lanthanide and actinide ions in dilute and concentrated chloride solutions

We have used EXAFS spectroscopy to investigate the inner sphere coordination of trivalent lanthanide (Ln) and actinide (An) ions in aqueous solutions as a function of increasing chloride concentration. At low chloride concentration, the hydration numbers and corresponding Ln,An-O bond lengths are as follows: La3+, N = 9.2, R = 2.54 A; Ce3+, N = 9.3, R = 2.52 A; Nd3+, N = 9.5, R = 2.49 A; Eu3+, N = 9.3, R = 2.43 A; Yb3+, N = 8.7, R = 2.32 A; Y3+, N = 9.7, R = 2.36 A; Am3+, N = 10.3, R = 2.48 A; Cm3+, N = 10.2, R = 2.45 A. In ca. 14 M LiCl, the early Ln3+ ions (La, Ce, Nd, and Eu) show inner sphere Cl- complexation along with a loss of H2O. The average chloride coordination numbers and Ln-Cl bond lengths are as follows: La3+, N = 2.1, R = 2.92 A; Ce3+, N = 1.8, R = 2.89 A; Nd3+, N = 1.9, R = 2.85 A; Eu3+, N = 1.1, R = 2.81 A. The extent of Cl- ion complexation decreases going across the Ln3+ series to the point where Yb3+ shows no Cl- complexation and no loss of coordinated water molecules. The actinide ions, Am3+ and Cm3+, show the same structural effects as the early Ln3+ ions, i.e., Cl- ion replacement of the H2O at high chloride thermodynamic activities. The Clion coordination numbers and An-Cl bond lengths are: Am3+, N = 1.8, R = 2.81 A; Cm3+, N = 2.4, R = 2.76 A. When combined with results reported previously for Pu3+ which showed no significant chloride complexation in 12 M LiCl, these results suggest that the extent of chloride complexation is increasing across the An3+ series. The origin of the differences in chloride complex formation between the Ln3+ and An3+ ions and the relevance to earlier work is discussed.     

Preferential oxidation of CO in excess H2 over CeO2/CuO catalyst:Effect of calcination temperature

Different from the classical configuration CuO/CeO2 catalyst,the inverse configuration CeO2 /CuO catalyst (atomic ratio of Ce/Cu=10/100) was prepared by impregnation method.Five calcination temperatures were selected to investigate the interaction between CeO2 and CuO support.It is found that as calcination temperature increased from 500 to 900 C,sintering of CeO2 particles on the support occurred together with the diffusion of a portion of Ce 4+ ions into CuO crystals,forming solid solution.Formation of interface complex Ce-O-Cu was suggested by TPR measurements.The catalyst calcined at 700 C gives the highest activity for preferential oxidation of CO in excess H2 stream.     

Probing the 4f states of ceria by tunneling spectroscopy

Low-temperature scanning tunneling microscopy and spectroscopy have been employed to analyze the local electronic structure of the (111) surface of a ceria thin film grown on Ru(0001). On pristine, defect-free oxide terraces, the empty 4f states of Ce(4+) ions appear as the only spectral feature inside the 6 eV oxide band gap. In contrast, occupied states are detected between -1.0 and -1.5 eV below E(Fermi) in conductance spectra of different point and line defects, such as surface oxygen vacancies, grain boundaries and step edges. They are assigned to partially filled 4f states localized at the Ce(3+) ions. The presence of excess electrons indicates the oxygen-deficient nature of the direct oxide environment. The f state spectroscopy with the STM allows us to probe the spatial distribution of Ce(3+) ions in the ceria surface, providing unique insight into the local reduction state of this chemically important material system.     

La2-xCexCu1-yZnyO4 perovskites for high temperature water-gas shift reaction

The performance of La2-xCexCu1-yZnyO4 perovskites as catalysts for the high temperature water-gas shift reaction (HT-WGSR) was inves-tigated. The catalysts were characterized by EDS, XRD, BET surface area, TPR, and XANES. The results showed that all the perovskites exhibited the La2CuO4 orthorhombic structure, so the Pechini method is suitable for the preparation of pure perovskite. However, the La1.90Ce0.10CuO4 perovskite alone, when calcined at 350/700℃, also showed a (La0.935Ce0.065)2CuO4 perovskite with tetragonal struc-ture, which produced a surface area higher than the other perovskites. The perovskites that exhibited the best catalytic performance were those calcined at 350/700 ℃ and, among these, La1.90Ce0.10CuO4 was outstanding, probably because of the high surface area associated with the presence of the (La0.935Ce0.065) 2CuO4 perovskite with tetragonal structure and orthorhombic La2CuO4 phase.     

Thermoluminescence study of persistent luminescence materials: Eu2+- and R3+-doped calcium aluminates, CaAl2O4:Eu2+,R3+

Thermoluminescence properties of the Eu2+-, R3+-doped calcium aluminate materials, CaAl2O4:Eu2+,R3+, were studied above room temperature. The trap depths were estimated with the aid of the preheating and initial rise methods. The seemingly simple glow curve of CaAl2O4:Eu2+ peaking at ca. 80 degrees C was found to correspond to several traps. The Nd3+ and Tm3+ ions, which enhance most the intensity of the high-temperature TL peaks, form the most suitable traps for intense and long-lasting persistent luminescence, too. The location of the 4f and 5d ground levels of the R3+ and R2+ ions were deduced in relation to the band structure of CaAl2O4. No clear correlation was found between the trap depths and the R3+ or R2+ level locations. The traps may thus involve more complex mechanisms than the simple charge transfer to (or from) the R3+ ions. A new persistent luminescence mechanism presented is based on the photoionization of the electrons from Eu2+ to the conduction band followed by the electron trapping to an oxygen vacancy, which is aggregated with a calcium vacancy and a R3+ ion. The migration of the electron from one trap to another and also to the aggregated R3+ ion forming R2+ (or R3+-e-) is then occurring. The reverse process of a release of the electron from traps to Eu2+ will produce the persistent luminescence. The ability of the R3+ ions to trap electrons is probably based on the different reduction potentials and size of the R3+ ions. Hole trapping to a calcium vacancy and/or the R3+ ion may also occur. The mechanism presented can also explain why Na+, Sm3+, and Yb3+ suppress the persistent luminescence.     

Magnetic properties of cyano-bridged Ln3+-M3+ complexes. Part I: trinuclear complexes (Ln3+ = La, Ce, Pr, Nd, Sm; M3+ = FeLS, Co) with bpy as blocking ligand

The reaction of Ln(NO3)3(aq) with K3[Fe(CN)6] or K3[Co(CN)6] and 2,2'-bipyridine in water/ethanol led to eight trinuclear complexes: trans-[M(CN)4(mu-CN)2{Ln(H2O)4(bpy)2}2][M(CN)6].8H2O (M = Fe3+ or Co3+, Ln = La3+, Ce3+, Pr3+, Nd3+, and Sm3+). The structures for the eight complexes [La2Fe] (1), [Ce2Fe] (2), [Pr2Fe] (3), [Nd2Fe] (4), [Ce2Co] (5), [Pr2Co] (6), [Nd2Co] (7), and [Sm2Co] (8) have been solved; they crystallize in the triclinic space group P and are isomorphous. They exhibit a supramolecular 3D architecture through hydrogen bonding and pi-pi stacking interactions. A stereochemical study of the nine-vertex polyhedra of the lanthanide ions, based on continuous shape measures, is presented. No significant magnetic interaction was found between the lanthanide(III) and the iron(III) ions.     

Self-assembly of lanthanide helicate coordination polymers into 3D metal-organic framework structures

Pyridine-2,6-dicarboxylic acid (pdcH(2) ) reacts with nitrate salts of La(III), Ce(III), and Nd(III) under hydrothermal conditions to form three-dimensional network structures, 1-4. All the compounds crystallize in the monoclinic space group P2(1)/c with the following lattice parameters: [La(2)(pdc)(3).3H(2)O] 1, a = 10.966(3) A, b = 17.534(4) A, c = 13.578(2) A, beta = 100.23(3) degrees, V( )()= 2569.3(9) A(3), Z = 4, R1 = 0.052, wR2 = 0.143, S = 1.06; [Ce(2)(pdc)(3).3H(2)O] 2, a = 12.701(3) A, b = 9.979(1) A, c = 19.401(4) A, beta = 97.73(2) degrees, V( )()= 2436.6(8) A(3), Z = 4, R1 = 0.039, wR2 = 0.117, S = 1.30; [Ce(2)(pdc)(3).3H(2)O] 3, a = 10.961(5) A, b = 17.523(5) A, c = 13.505(2) A, beta = 100.89(3) degrees, V( )()= 2547.2(8) A(3), Z = 4, R1 = 0.040, wR2 = 0.103, S = 1.08; [Nd(2)(pdc)(3).3H(2)O] 4, a = 10.944(3) A, b = 17.448(5) A, c = 13.397(2) A, beta = 101.19(3) degrees, V( )()= 2569.3(9) A(3), Z = 4, R1 = 0.052, wR2 = 0.143, S = 1.06. Compounds 1, 3, and 4 form infinite single helical chains with large widths and pitches containing four metal ions per turn while 2 forms a different helix with smaller width and pitch containing two metal ions per turn. Each helix is further bonded on either side via carboxylate bridging producing three-dimensional metal-organic framework structures.