K2Ln(NO3)5·2H2O(Ln=La,Ce,Pr,Nd,Sm)的晶体生长和热重-差热分析研究

本文生长出了K₂Ln（NO₃）₅·2H₂O（Ln=La；Ce；Pr；Nd；Sm）的单晶，并对其进行了晶体结构及差热-热重分析研究．结果表明，K₂Ln（NO₃）₅.2H₂O（Ln=La；Ce；Pr；Nd）的晶体属正交晶系，Fdd2空间群．首次生长出KPrN单晶并用直接法解出其晶体结构．解得KPrN的晶胞参数为：a=11．2210（10）A, b=21．411（3）A，c=12．208（2）A,Z=6；R=0．0240．对KLnN加热，则依次出现脱水、熔化、不可逆相变和NO的分解过程（K₂Ce（NO₃）₅·2H₂O除外）K₂Ln（NO₃）₅·2H₂O（Ln＝La；Nd；Sm）的NO分三步分解，K₂Ln（NO₃）₅·2H₂O（Ln=Ce；Pr）的NO分两步分解·KNO₃和Ln（NO₃）₃·nH₂O的混合物在225℃左右生成K₂Ln（NO₃）₅     

Ln2O2S:Yb,Pr(Ln=Y、La)纳米材料的上转换发光研究

研究乙醇辅助燃烧法制备的纳米Ln2O2S:Yb,Pr(Ln=Y、La)的上转换发光特性.Ln2O2S:Yb,Pr纳米上转换发光材料在980hm激光泵浦下,呈现明亮的蓝绿色发光.Ln2O2S:Yb,Pr的发射光谱峰值为514nm,而Ln2O2S:Yb,Pr的发射光谱峰值为508nm,属于Pr3+的3P0→H4跃迁.这是由于Pr3+离子的5d轨道与4f轨道很接近,其f-f跃迁受Pr3+离子周围晶场环境影响很大,其上转换发光光谱在不同基质中有较大不同.     

Ln_2O_2S∶Yb,Pr(Ln=Y、La)纳米材料的上转换发光研究

研究乙醇辅助燃烧法制备的纳米Ln2O2S∶Yb,Pr(Ln=Y、La)的上转换发光特性。Ln2O2S∶Yb,Pr纳米上转换发光材料在980nm激光泵浦下,呈现明亮的蓝绿色发光。Y2O2S∶Yb,Pr的发射光谱峰值为514nm,而La2O2S∶Yb,Pr的发射光谱峰值为508nm,属于Pr3+的3P0→3H4跃迁。这是由于Pr3+离子的5d轨道与4f轨道很接近,其f-f跃迁受Pr3+离子周围晶场环境影响很大,其上转换发光光谱在不同基质中有较大不同。     

中温固体氧化物燃料电池阴极材料Ln_(0.6)Sr_(0.4)Fe_(1-χ)Co_χO_(3-δ)的合成和性能表征

采用固相反应法合成了中温固体氧化物燃料电池阴极材料Ln0.6Sr0.4Fe1-χCoχO3-σ（Ln=La,Pr;Nd,Sm和Gd）粉体.对其进行结晶学表征,分析氧含量和失重与温度的关系,并研究了其电导率随温度的变化规律及其与Ce0.8Gd0.2O1.9（CGO）电解质的化学相容性.实验表明,600～800℃;所有样品的电导率均高于100S/cm,其中Nd0.6Sr0.4Co0.8Fe0.2O3-σ的电导率高达600S/cm,并且与CGO电解质都具有良好的化学相容性.     

Lattice Effect on Magnetic and Electrical Properties of Ln2/3Pb1/3MnO3 （Ln=La,Pr, Nd） Films

Lattice effect on magnetic and electrical transport properties of Ln2/3Pb1/3MnO3 （Ln=La, Pr, Nd） films prepared by RF magnetron sputtering technique were investigated. With the decrease of the average ions radius 〈rA〉, the structure of Ln2/3Pb1/3MnO3 （Ln=La, Pr, Nd） targets transit from the rhombohedral phase to the orthorhombic phase, and the Curie temperature reduces rapidly with the decrease of 〈rA〉. The electrical properties show that films are the metallic state which can be fitted to the formula： ρ（T）=ρ0 ＋ ρ1T^2 ＋ ρ2T^4.5 at low temperatures. The temperature range of the ferromagnetic metallic state becomes narrow with the decrease of 〈rA〉. The phenomenon can be explained by the lattice effect.     

苯甲酸系列邻菲啰啉硝酸根稀土四元混配配合物的合成、表征和抗菌活性研究

在酸性介质 ,乙醇 /水混合溶剂中合成得到了四元混配配合物 [Ln(C6 H5COO) 2 (NO3)(phen) ]2 (Ln =La ,Ce ,Pr ,Nd ,Sm ,Eu ,Gd ,Er ,Tm)和 [Nd(x MBA) 2 (NO3) (phen) ]2 (x =o、p、m) (MBA =甲基苯甲酸 )。用元素分析、IR和UV方法对配合物进行了表征 ,并对配合物的抗枯草杆菌、大肠杆菌、金黄色葡萄球菌、酵母菌、白念珠菌、和霉菌的性能进行了研究。     

(Mg0.05La0.45Sm0.5)2(Zr0.7Ce0.3)2O6.95陶瓷的制备与导热性能研究

以MgCl2·6H2O、La2O3、Sm2O3、ZrOCl2·8H2O和Ce(NO3)3·6H2O为原料,采用化学共沉淀法合成了一种新型的多元稀土锆酸盐( Mg0.05La0.45Sm0.5)2(Zr0.7Ce0.3)2O6.95陶瓷粉体,在1600℃无压烧结10h制备了致密的陶瓷块体,用X射线衍射仪(XRD)及场发射扫描电镜(SEM)对其微观组织结构进行了表征,采用激光闪射法测试了块体的导热性能.结果表明,制备的多元稀土锆酸盐陶瓷材料具有焦绿石结构,晶粒细小,陶瓷的热导率明显低于一元稀土锆酸盐Sm2Zr2O7和二元(La0.5 Srn0.5)2(Zr0.7Ce03)2O7的热导率.该研究结果显示(Mg0.05 La0.45 Sm0.5)2 (Zr0.7 Ce0.3)2O6.95多元稀土锆酸盐陶瓷有可能应用于热障涂层陶瓷层材料.     

钙钛矿锰氧化物（La0.8Ln0.2）2/3Ca1/3MnO3（Ln=La，Ce，Pr，Nd，Sm，Eu）的低场电输运性能分析

用溶胶-凝胶法制备了系列掺杂（La0.8Ln0.2）2/3Ca1/3MnO3（Ln=La,Ce,Pr,Nd,Sm,Eu）纳米级晶体。对比在La被其它镧系元素部分替代后,引起的A位离子平均半径的改变和磁矩变化对电输运及磁阻性能的影响,实验分析表明,各个样品在同样大小磁场下的磁电阻存在较大的差别,样品的磁电阻随原子序数的增加而明显变大,由镧系收缩引起晶格畸变所产生的本征磁电阻占主导地位,随着外加磁场的增加,不同掺杂样品间的峰值电阻差异被弱化;各掺杂样品间的转变温度差与掺杂离子半径差和磁矩差密切相关,且离子半径的差异对转变温度的改变贡献更大。     

稀土元素掺杂纳米TiO2Zeta电位的研穷

采用溶胶-凝胶法制备纳米TiO2以及稀土元素（Ce、Nd、Pr、Sm）掺杂纳米TiO2粉体．采用透射电镜（TEM）表征粉体形貌，MARVEN NANO ZS-90仪器测试粉体Zeta电位。结果表明：制备粉体属于纳米级别；在pH值2～11范围内，Pr、Sm、Nd掺杂与纯纳米TiO2 Zeta电位-pH曲线形状大致相同，相对于纳米TiO2的Zeta电位-pH曲线，Pr、Sm掺杂曲线右移，等电点增大；Nd掺杂曲线左移，等电点减小。Ce掺杂未出现等电点，在pH值2～11范围内，其Zeta电位始终为负值，在pH值相同时，5％Ce-TiO2 Zeta电位绝对值〉1％Ce-TiO2、2．5％Ce-TiO2．     

中温固体氧化物燃料电池阴极材料Ln0.6Sr0.4Fe1-χCoχO3-δ的合成和性能表征

采用固相反应法合成了中温固体氧化物燃料电池阴极材料Ln0.6Sr0.4Fe1-xCoxO3-δ（Ln＝La，Pr,Nd,Sm和Gd）粉体。对其进行结晶学表征，分析氧含量和失重与温度的关系，并研究了其电导率随温度的变化规律及其与Ce0.8Gd0.2O1.9（CGO）电解质的化学相容性。实验表明，600－800℃，所有样品的电导率均高于100S/cm，其中Nd0.6Sr0.4Co0.8Fe0.2O3－δ的电导率高达600S／cm，并且与CGO电解质都具有良好的化学相容性。     

Electrical properties of Ln2Mo2O7 pyrochlores (Ln=SmYb,Y)

Cubic oxide pyrochlores, Ln₂Mo₂O₇, Ln=SmYb,Y, (Nd_1?xA_x), A=Er and Yb; 0 < x < 1.0, have been synthesized and electrical properties were examined in the range 77-600K. Semiconductor behavior is observed for Ln=EuYb, Y but the resistivity and E_a are low. Sm₂Mo₂O₇ and Nd_1?xYb_xMo₂O₇ (0.05 ≤ x ≤ 0.1) exhibit semimetallic or metallic behavior. The mechanism of conduction in these compounds is explained on the basis of band model proposed by Sleight et al.     

Nuclear microanalysis of amorphous As2Se3 films modified with Ln(thd)3 (Ln = Eu, Tb)

The compositions of amorphous As₂Se₃ thin films modified with the Ln(thd)₃ (Ln = Eu, Tb) complexes have been determined by nuclear microanalysis using deuterons provided by an electrostatic accelerator: Rutherford backscattering spectroscopy and nuclear reaction analysis. The rare-earth, oxygen, and carbon contents have been determined as functions of the initial concentration of the complex. The films have been also characterized by IR spectroscopy. Analysis of the nuclear microanalysis and IR spectroscopy results suggests that, in the modified films, the rare-earth atoms retain their local environment, in contrast to thin films of amorphous hydrogenated silicon.     

Surface characterization and catalytic activity of Ln2Ti2O7 (Ln=Y,Sm, Gd and Tb)

The surface of the catalyst, Ln₂Ti₂O₇ where Ln=Y, Sm, Gd and Tb was analysed by X-ray photoelectron spectroscopy. Terbium is found to be present in 3⁺ and 4⁺ states while Y, Sm and Gd are present in the 3⁺ state. The catalytic activity of these oxides was tested using decomposition of N₂O as the test reaction and the catalytic activity was correlated to the surface properties.     

Preparation of Ln2O2S (Ln = Gd,Dy, Y,Er, Lu) in flowing hydrogen and hydrogen sulfide

The exposure of anhydrous Ln₂(SO₄)₃ (Ln = Gd, Dy, Y, Er, Lu) sulfates to flowing hydrogen in the range 500–1050°C leads to the formation of Ln₂O₂S + Ln₂O₃ materials. With increasing reaction temperature, the mole fraction of Ln₂O₂S in the samples decreases. Single-phase Ln₂O₂S (Ln = Gd, Dy, Y, Er, Lu) compounds have been obtained by exposing the rare-earth sulfates first to flowing hydrogen in the range 500–600°C and then to hydrogen sulfide in the range 850–950°C.     

Synthesis and magnetic properties of Cr2Ln6S11 (Ln = Gd, Tb, Er, Ho)

The CrS-Er₂S₃ phase diagram was studied, and the stability limits of CrEr₂S₄, CrEr₄S₇, Cr₂Er₆S₁₁, and Cr₃Er₈S₁₅ were determined. The compounds Cr₂Ln₆S₁₁ (Ln = Gd, Tb, Er, Ho) were prepared, and their magnetic properties were investigated. All these sulfides were found to be paramagnetic in the temperature range 80–300 K     

Controlled processing of (Gd,Ln)2O3:Eu (Ln = Y,Lu) red phosphor particles and compositional effects on photoluminescence

Synthesis of (Gd_0.95−xLn_xEu_0.05)₂O₃ (Ln = Y and Lu, x = 0–0.95) powders via ammonium hydrogen carbonate (AHC) precipitation has been systematically studied. The best synthesis parameters are found to be an AHC/total cation molar ratio of 4.5 and an ageing time of 3 h. The effects of Y³⁺ and Lu³⁺ substitution for Gd³⁺, on the nucleation kinetics of the precursors and structural features and optical properties of the oxides, have been investigated. The results show that (i) different nucleation kinetics exist in the Gd–Y–Eu and Gd–Lu–Eu ternary systems, which lead to various morphologies and particle sizes of the precipitated precursors. The (Gd,Y)₂O₃:Eu precursors display spherical particle morphologies and the particle sizes increase along with more Y³⁺ addition. The (Gd,Lu)₂O₃:Eu precursors, on the other hand, are hollow spheres and the particle sizes increase with increasing Lu³⁺ incorporation, (ii) the resultant oxide powders are ultrafine, narrow in size distribution, well dispersed and rounded in particle shape, (iii) lattice parameters of the two kinds of oxide solid solutions linearly decrease at a higher Y³⁺ or Lu³⁺ content. Their theoretical densities linearly decrease with increasing Y³⁺ incorporation, but increase along with more Lu³⁺ addition and (iv) the two kinds of phosphors exhibit typical red emissions at ∼613 nm and their charge-transfer bands blue shift at a higher Y³⁺ or Lu³⁺ content. Photoluminescence/photoluminescence excitation intensities and external quantum efficiency are found to decrease with increasing value of x, and the fluorescence lifetime mainly depends on the specific surface areas of the powders.     

Structural transitions in (La,Ln)2CuO4 and La2(Cu,Ni)O4 systems

Solid solutions of the formula La_2?xLn_xCuO₄ (Ln = Pr, Nd) possess the orthorhombic structure of La₂CuO₄ for small values of x and transform to the tetragonal Nd₂CuO₄ structure at a critical value of x. At the critical composition, there is an abrupt change in specific volume as well as the $\text{c}\text{a}$ ratio. The material exhibits temperature-independent electrical resistivity below the critical value x and semiconducting behaviour above it. The specific volume and $\text{c}\text{a}$ ratio smoothly decrease with increase in x in the La₂Cu_1?xNi_xO₄ system, although the solid solution possess the tetragonal K₂NiF₄ structure when x>0.1. Compositions with x>0.1 exhibit a gradual semiconductor metal transition similar to that of La₂NiO₄, the transition temperature decreasing with increasing x.