LED用红色发光材料 Li3Ba2Ln3-xEux(MoO4)8的制备及性能

采用溶胶-凝胶法合成了发光二极管(LED)用的系列红色荧光粉Li₃Ba₂Ln_3-xEu_x(MoO₄)₈ (Ln=La, Gd, Y)。利用差热-热重(TG-DTA)分析和粉末X 射线衍射(XRD)测定了其最佳合成温度和不同温度下所得样品的结构,发现所有样品均具有单斜结构;采用荧光光谱对所得荧光粉发光性能进行了表征,发现在相同条件下所得样品的发光强度顺序为:Li₃Ba₂Y_2.8Eu_0.2(MoO₄)₈＞Li₃Ba₂Gd_2.8Eu_0.2(MoO₄)₈＞Li₃Ba₂La_2.8Eu_0.2-(MoO₄)₈。它们在395 nm和465 nm的激发光源激发时均有强的吸收,与LED芯片发射波长相匹配。同时分析了柠檬酸及分散剂聚乙二醇(PEG-10000)的用量、Eu³⁺离子的浓度以及焙烧温度等因素对荧光粉发光性能的影响。     

Eu3+:Ln2O2S(Ln=Lu,Y,Gd,La)晶体的角重迭参数计算

本文使用角重迭模型(AOM),针对Eu3+:Ln2O2S(Ln=Lu,Y,Gd,La)晶体系列,在考虑硫和氧两种不同格位的情况下,对f电子的全部四个角重迭参数eσ、eπ、eδ和eφ进行了计算,得到了一些基本规律,即中心离子与配位体之间的共价性大小次序为Lu～Y>Gd>La,并且Ln-O键的共价性要强于Ln-S键.     

LnAlO3中Ce3+,Tb3+,Dy3+的发光及Ce-Tb,Ce-Dy的敏化发光(Ln=La,Gd,Y)

本文采用BaF2作为助熔剂和抑制剂经固相反应合成了一系列以LnAlO3(Ln=La,Gd,Y)为基质的磷光体,系统地研究了LnAlO3中Ce3+,Tb3+,Dy3+的发光及Ce-Tb,Ce-Dy的敏化发光,发现随Ln的不同,LnAlO3作为基质对激活剂的发光性质的影响也不同,本文得到一些规律性结果,并作了讨论。     

稀土配合物RE(TPTZ)Cl_3的合成、表征及荧光性能研究

首次以2,4,6-三吡啶基三嗪（TPTZ）与Sm, Eu, Tb和Dy氯化物反应,合成四种单一稀土配合物以及Tb分别1∶1掺Gd, Y, La的三种异核配合物。经元素分析、稀土络合滴定、摩尔电导率、红外光谱、紫外光谱和差热-热重测定表明,配合物的组成分别为RE（TPTZ）Cl3·3H2O（RE=Sm, Eu, Tb, Dy）和Tb0.5Ln0.5（TPTZ）Cl3·3H2O（Ln=Gd, Y, La）;TPTZ作为三齿配体与稀土离子配位,即中心环提供一个N原子,两个吡啶环分别提供一个N原子;配合物中3个水分子与稀土离子配位,1个Cl-在外界,2个在内界,为1∶1型电解质;配合物内外界可能为[RE（TPTZ）（H2O）3Cl2] Cl,稀土离子的配位数为8。配合物的荧光光谱测试表明,四种单一稀土配合物中,Tb配合物发光最强;三种1∶1掺杂异核Tb配合物荧光强度大于纯Tb配合物,表明Y3＋, La3＋和Gd3＋都可以敏化Tb3＋的发光,其中Gd3＋的敏化作用最强,Y3＋次之,La3＋最差。     

Observation of two time scales in the ferromagnetic manganite La1-xCaxMnO3, x approximately 0.3

We report new zero-field muon spin relaxation and neutron spin echo measurements in ferromagnetic (FM) (La,Ca)MnO3 which suggest at least two spatially separated regions possessing very different Mn-ion spin dynamics. One region displays diffusive relaxation, "critical slowing down" near T(C) and an increasing volume fraction below T(C), suggesting overdamped FM spin waves below T(C). The second region possesses more slowly fluctuating spins, a linewidth independent of q, and a decreasing volume fraction below T(C). The estimated length scale for the inhomogeneity is 相似文献   

Tb1-xLnxA3(A=对氨基苯甲酸,x=0-0.9)固体配合物的光谱分析和荧光增强

合成了一系列组成为 Tb1-x Lnx A3 (L n=Gd、Y、La,A=对氨基苯甲酸 ,x=0— 0 .9)的固体配合物。利用红外光谱和荧光光谱研究了配合物的结构和荧光性质 ,结果表明 ,掺杂配合物的结构与未掺杂的对氨基苯甲酸铽相似。荧光光谱的结果显示 ,Gd3 对 Tb3 的发光有明显的增敏作用 ,探讨了荧光增敏机理。     

配合物La（C5O3H3）3·C12H8N2·H2O的合成和表征

本以α－呋喃甲酸（Ｃ５Ｏ３Ｈ４）和邻菲罗啉（Ｃ１２Ｈ８Ｎ２）为配体,在乙醇８溶剂中与硝酸镧反应,合成了与稀土离子Ｌａ（Ⅲ）的三元混配配合物。经元素分析确定其配合物的组成为Ｌａ（Ｃ５Ｏ３Ｈ３）·Ｃ１２Ｈ８Ｎ２·Ｈ２Ｏ,同时还通过了ＩＲ、＾１ＨＮＭＲ、ＵＶ、ＴＧ－ＤＴＡ等谱光的测试与分析,表征了配合物的组成结构和性质。ＩＲ、＾１ＨＮＭＲ和ＵＶ谱的分析结果表明配体羧酸是以脱质子的酸根形式与中心稀土离子     

对含Y_2O_3和Gd_2O_3的La_2O_3-B_2O_3-BaO玻璃化学稳定性研究

本文研究了含Ｙ２Ｏ３和Ｇｄ２Ｏ３的Ｌａ２Ｏ３－Ｂ２Ｏ３－ＢａＯ玻璃的耐水性和耐酸性。结果表明，比硅酸盐玻璃化学稳定性差的Ｌａ２Ｏ３－Ｂ２Ｏ３－ＢａＯ玻璃，可以适量的用Ｙ２Ｏ３和Ｇｄ２Ｏ３取代Ｌａ２Ｏ３，可得以改善     

激光烧蚀Al热原子与CF4,CCl4,CH2Br2反应中激发态C2的形成

脉冲激光烧蚀平面铝靶产生的热原子与气相CF4,CCl4,CH2Br2的碰撞反应中,在430～600nm之间观测到激发态C2分子的发光光谱,它们可归属为Swan带的d^3Ⅱg=a^3Ⅱu跃迁中△v=2,1,0,-1,-2五个振动序列(v′≤6)。谱强度分析表明,C2激发态可很好的用热平衡描述,其振动温度达6000K左右。同时在△v=0和-1的振动带间观测到振荡的谱峰,它们是转动谱线叠加的结果。激光烧蚀Al产生的等离子体在膨胀中产生的激波及其本身的动能与反应气体碰撞使其解离产生C,然后复合形成C2。C2激发态d可能是通过激发态的Al(^2S)经近共振传能产生,也不排除在有足够碰撞能下优先形成C2激发态b,再通过与d态的v′=6能级交叉无辐射跃迁而进入d态。     

Correlation of photoluminescence of (Y, Ln)VO4:Eu (Ln=Gd and La) phosphors with their crystal structures

We have studied the photoluminescence (PL) of (Y, Ln)VO₄:Eu³⁺ (Ln=La and Gd) phosphors and the correlation of the PL of those phosphor with their crystal structure. It is found that (Y, Gd)VO₄:Eu³⁺ phosphors have the same crystal structure as YVO₄:Eu³⁺, which is tetragonal with a little different lattice parameters. In the case of (Y, La)VO₄:Eu³⁺ phosphors, however, the gradual change from tetragonal to monoclinic structure of host lattice was observed as the amount of La ion increased. To investigate the PL property of (Y, Ln)VO₄:Eu³⁺ (Ln=La and Gd) phosphors, vacuum ultraviolet (VUV) and ultraviolet (UV) excitation were used. The favorable crystal structure for the PL intensity of orthovanadate phosphor under 147 and 254 nm excitation was tetragonal containing Gd ion and under 365 nm excitation was monoclinic containing La ion which might have the lowest site symmetry for Eu³⁺ ion.     

Y_2O_3和Gd_2O_3对含La_2O_3硼酸盐玻璃析晶性能的影响

用差热分析（ＤＴＡ）、Ｘ射线衍射分析（ＸＲＤ）方法研究了Ｙ２Ｏ３和Ｇｄ２Ｏ３对７０Ｂ２Ｏ３２５Ｌａ２Ｏ３５ＺｎＯ（ｍｏｌ％）玻璃析晶性能的影响；用梯温炉测定比较了Ｙ２Ｏ３和Ｇｄ２Ｏ３对玻璃失透倾向的影响；用红外光谱（ＩＲ）研究了Ｙ２Ｏ３和Ｇｄ２Ｏ３在玻璃中的结构作用。结果表明，适量用Ｙ２Ｏ３或Ｇｄ２Ｏ３取代Ｌａ２Ｏ３可以减轻玻璃的失透倾向，但没有改变玻璃的析晶相。玻璃的析晶相是ＬａＢ３Ｏ６，Ｙ２Ｏ３和Ｇｄ２Ｏ３在玻璃结构中为网络修饰体。玻璃的折射率ｎｄ高于１．７０，色散系数υ低于５５。     

A3Ln(Ⅲ)1-xTb(Ⅲ)x(A=邻氨基苯甲酸;Ln=La、Gd、Y; x=0-0.1)稀土配合物的荧光性能

采用共沉淀法合成了掺杂 L a、 Gd、 Y的 Tb-邻氨基苯甲酸配合物 ,研究其荧光性能 ,结果显示 ,掺杂L a、Gd、Y后 ,对 Tb配合物的发光有增敏作用 ,讨论了不同的掺杂离子 (L a、Gd、Y)及掺杂量对其荧光性能的影响。发现 ,当掺杂离子取代大部分 Tb3+时 ,其发光增强仍十分显著。     

Structural anomalies associated with the electronic and spin transitions in LnCoO<Subscript>3</Subscript>

A powder X-ray diffraction study, combined with magnetic susceptibility and electric transport measurements, was performed on a series of LnCoO₃ perovskites (Ln = Y, Dy, Gd, Sm, Nd, Pr and La) over a temperature range 100–1000 K. A non-standard temperature dependence of the observed thermal expansion was modelled as a sum of three contributions: (1) weighted sum of lattice expansions of the cobaltite in the diamagnetic low spin state and in the intermediate (IS) or high (HS) spin state. (2) An anomalous expansion due to the increasing population of excited (IS or HS) states of Co³⁺ ions over the course of the diamagnetic-paramagnetic transition. (3) An anomalous expansion due to excitations of Co³⁺ ions to another paramagnetic state accompanied by an insulator-metal transition. The anomalous expansion is governed by parameters that are found to vary linearly with the Ln ionic radius. In the case of the first magnetic transition it is the energy splitting E between the ground low spin state and the excited state, presumably the intermediate spin state. The energy splitting E, determined by a fit to magnetic susceptibility, decreases with temperature. The values of E determined for LaCoO₃ and YCoO₃ at T=0 K are 164 K and 2875 K respectively, which fall to zero at T=230 K for LaCoO₃ and 860 K for YCoO₃. The second anomalous expansion connected with a simultaneous magnetic and insulator-metal transition is characterized by its center at T=535 K for LaCoO₃ and 800 K for YCoO₃. The change of the unit cell volume during each transition is independent of the Ln cation and is about 1% in both cases.     

光谱纯Y2O3,La2O3,Lu2O3中微量杂质的光致发光谱研究

测定了光谱纯稀土化合物Ｙ２Ｏ３，Ｌａ２Ｏ３，Ｌｕ２Ｏ３中微量杂质在４８８．０ｎｍ和５１４．５ｎｍ激光线激发下的光致发光谱以及在可见光４４５～７４１ｎｍ范围内吸收谱，Ｙ２Ｏ３，Ｌｕ２Ｏ３样品在４４８．０ｎｍ和５１４．５ｎｍ激光激发下都有发光效应，而Ｌａ２Ｏ３样品只在４８８．０ｎｍ激光激发下才发光，分析了结果表明，Ｙ２Ｏ３，Ｌａ２Ｏ３，Ｌｕ２Ｏ３的发光谱分别是由其存在的微量Ｅｒ＾３＋，Ｓｍ＾３＋和Ｅｕ     

Effect of disorder outside the CuO2 planes on Tc of copper oxide superconductors

The effect of disorder on the superconducting transition temperature T(c) of cuprate superconductors is examined. Disorder is introduced into the cation sites in the plane adjacent to the CuO2 planes of two single-layer systems, Bi(2.0)Sr(1.6)Ln(0.4)CuO(6+delta) and La(1.85-y)Nd(y)Sr0.15CuO4. Disorder is controlled by changing rare earth (Ln) ions with a different ionic radius in the former, and by varying the Nd content in the latter with the doped carrier density kept constant. We show that this type of disorder works as weak scatterers in contrast to the in-plane disorder produced by Zn, but remarkably reduces T(c), suggesting novel effects of disorder on high-T(c) superconductivity.     

Common energy scale for magnetism and superconductivity in underdoped cuprates: a muon spin resonance investigation of (Ca(x)La(1-x)) (Ba(1.75-x)La(0.25+x))Cu3O(y)

We characterize the spontaneous magnetic field, and determine the associated temperature T(g), in the superconducting state of (Ca(x)La(1-x)) (Ba(1.75-x)La(0.25+x)) Cu(3)O(y) using zero and longitudinal field muon spin resonance measurements for various values of x and y. Our major findings are (i) T(g) and T(c) are controlled by the same energy scale, (ii) the phase separation between hole poor and hole rich regions is a microscopic one, and (iii) spontaneous magnetic fields appear gradually with no moment size evolution.     

Y替代La2/3Ca1/3MnO3体系的结构与输运行为

系统研究了(La1-xYx)2/3Ca1/3MnO3(0.0≤x≤0.3)体系的结构和输运行为.结果表明，实验样品具有很好的单相结构，随Y掺杂浓度的增加，金属—绝缘体（M—I）转变温度T-MI向低温区移动，对应的峰值电阻率ρp升高，对x=0.3样品，较未替代样品（x=0.0）增幅达8个数量级.在外加磁场下，材料表现出很强的磁电阻效应.同时，从实验结果出发，直接给出了输运特性与晶体结构之间的关联，并从双交换模型和可变程跃迁理论出发，对实验结果进行了初步讨论. 关键词： La2/3Ca1/3MnO3锰氧化物 Y替代 晶体结构 输运行为     

Positive muon spin precession in magnetic oxides MnO and V2O3; local fields and phase transition

Muon spin precession is observed in the ordered state of antiferromagnetic oxides MnO and V₂O₃. An anomalous temperature dependence of muon precession frequency and the absence of critical behavior atT _N are found in MnO and a hysterisis of the transition temperature is observed in V₂O₃. These results are explained in terras of the crystal distortion of these materials belowT _N.We would like to thank Dr. T. Suzuki, Dr. S. Takagi, Dr. Y. Kuno and Dr. C.Y. Huang for their help in the measurements, and Dr. K. Kosuge and Dr. S. Kachi for providing the specimen of V₂O₃. We are grateful to the financial support from Japan Society for Promotion of Science.     

对靶溅射技术制备的La2/3Ca1/3MnO3/YBa2Cu4O8/La2/3Ca1/3MnO3薄膜中Tc的降低

本文用对靶溅射技术制备了La2/3Ca1/3MnO3/YBa2Cu4O8/La2/3Ca1/3MnO3薄膜.与YBCO单层薄膜相比,由于超导/铁磁系统中的磁性邻近效应,三层薄膜表现出较低的超导转变温度.薄膜的R～T测量曲线显示出超磁阻(CMR)效应和超导转变,预示着超导和铁磁特性共存于LCMO/YBCO/LCMO三文治结构.     

Noise probe of the dynamic phase separation in La(2/3)Ca(1/3)MnO3

Giant random telegraph noise (RTN) in the resistance fluctuation of a macroscopic film of perovskite-type manganese oxide La(2/3)Ca(1/3)MnO3 has been observed at various temperatures ranging from 4 to 170 K, well below the Curie temperature ( T(C) approximately 210 K). The amplitudes of the two-level fluctuations vary from 0.01% to 0.2%. We discuss the origin of the RTN to be a dynamic mixed-phase percolative conduction process, where manganese clusters switch back and forth between two phases that differ in their conductivity and magnetization.