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1.
采用固相反应的方法;经二次灼烧合成了掺Ce(3+)、Tb(3+)的Ca3Y2(BO3)4和Sr3Y2(BO3)4磷光体;分析了合成过程中铈的还原情况.用X-射线衍射分析确定了它们的结构均为正交晶系,空间群P21cn测定了Ce(3+)和Tb(3+)在两种基质中的光谱,得到Ce(3+)波长位移的某些规律,观察到Ce(3+)对Tb(3+)的敏化作用.  相似文献   

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利用脉冲激光法研究了在(100)SrTiO3(STO)、(100)LaAlO3(LAO)和(100)Y-ZrO2(YSZ)衬底上外延生长LaCuO4(LCO),La1.85Sr0.15CuO4(LSCO),Nd1.85Ce0.15CuO4(NCCO)和Pr2CuO4(PCO)薄膜的工艺技术。利用X光衍射仪检测了不同条件下制备的薄膜样品结构和取向。X射线衍结果表明,在事适的制膜条件下可以在这三种衬底  相似文献   

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用浸渍法制备了CuO/Al2O3 (Cu/Al)、CuO/CeO2- Al2O3 (Cu/CeAl)和CuO/La2O3-Al2O3(Cu/LaAl)催化剂. 通过原位XRD、Raman和H2-TPR方法, 对催化剂中的CuO物种以及CuO-Al2O3的固-固相反应进行了表征. 结果表明,对于Cu/Al催化剂,CuAl2O4存在于CuO与Al2O3层之间,CuO以高分散和晶相两种相态存在于催化剂的表层;对于Cu/CeAl催化剂,除了少量高分散和晶相的CuO存在于表层外,大部分CuO迁移到了CeO2的内层,  相似文献   

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Electronic charge order is a symmetry breaking state in high-Tc cuprate superconductors. In scanning tunneling microscopy, the detected charge-order-induced modulation is an electronic response of the charge order. For an overdoped(Bi,Pb)2Sr2CuO6+x sample, we apply scanning tunneling microscopy to explore local properties of the charge order. The ordering wavevector is nondispersive with energy, which can be confirmed and determined. By extracting its order-parameter field, we identify dislocations in the stripe structure of the electronic modulation, which correspond to topological defects with an integer winding number of ±1. Through differential conductance maps over a series of reduced energies, the development of different response of the charge order is observed and a spatial evolution of topological defects is detected. The intensity of charge-order-induced modulation increases with energy and reaches its maximum when approaching the pseudogap energy. In this evolution, the topological defects decrease in density and migrate in space. Furthermore, we observe appearance and disappearance of closely spaced pairs of defects as energy changes. Our experimental results could inspire further studies of the charge order in both high-Tccuprate superconductors and other charge density wave materials.  相似文献   

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实验上研究了(La1-xSrx)2CuO4)高Tc单晶样品的c-轴正常态电阻同温度的关系以及Tc附近c-轴电阻作为磁场和磁场取向的函数,结果表明,(1)随着Sr含量的增加,c-轴正常态电阻从半导体行为变为金属行为,和(2)固有的各向异性随Sr含量的增加而逐渐变弱,这些意味着Sr掺杂在La基系统中有利于Cu-O面间耦合的改善。  相似文献   

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研究了提拉法生长的掺Er^3+的Sr3Y2(BO3)4晶体的吸收光谱和荧光光谱。应用J—O理论分析并计算了光谱参数,得到唯象参数Ω2、Ω4和Ω6分别为11.90×10^-20cm^2、3.44×10^-20cm^2和1.92×10^-20cm^2。在Er^3+:Sr3Y2(BO3)4晶体中,Er^3+在1533nm波长的发射截面为1.00×10^-20cm^2,^4I13/2→^I15/2能级跃迁的荧光寿命和辐射寿命分别为0.58ms和4.10ms,良好的光谱性能表明Er^3+:Sr3Y2(BO3)4晶体可能成为潜在的1.55μm波段的一种激光材料。  相似文献   

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吴坚  张世远 《中国物理》2003,12(7):792-795
A series of (La_{1-x}Tb_x)_{2/3}Sr_{1/3}MnO_3 polycrystalline samples has been studied by means of x-ray diffraction, magnetostriction, and thermal expansion measurements. It has been found that this series undergoes a phase transition from a rhombohedral to an orthorhombic form at the doping level x≈0.20 at room temperature accompanied by an anisotropic magnetostriction up to -50×10^{-6} under a magnetic field of 1T. The linear and volume magnetostrictions vary with chemical composition, even change sign. At T=80K, the magnetostrictions for the samples of x=0.20 and 0.40 exhibit different behaviours. The sample of x=0.20 has positive volume and linear magnetostrictions and a negative anisotropic magnetostriction, while the sample of x=0.40 has an opposite behaviour. The magnitude of volume magnetostriction for both the samples is essential (~10^{-4}) at T=80K under a magnetic field of 4T. We conclude that these anomalous effects are due to the charge delocalization and the structural phase transition between orthorhombic and rhombohedral forms induced by the applied magnetic field.  相似文献   

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A blue emitting phosphor Sr3Bi(PO4)3:Eu2+ is synthesized luminescent property is investigated. Sr3Bi(PO4 )3 :Eu^2+ can by a high-temperature solid state method, and its create blue emission under the 332 radiation excitation, and the prominent luminescence in blue (423nm) due to the 4fSd^1→4f^7 transition of the Eu^2+ ion. The crystallographic sites of the Eu^2+ ion in Sr3Bi(PO4)3 are analyzed, and the 420 and 440 nm emission peaks of the Eu^2+ ion are assigned to the nine-coordination and eight-coordination, respectively. The emission intensity of Sr3Bi(PO4)3:Eu^2+ is influenced by the Eu^2+ doping content, and the concentration quenching effect is observed. The quenching mechanism is the dipole-dipole interaction, and the critical distance of energy transfer is calculated by the concentration quenching method to be approximately 1.72nm.  相似文献   

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Evidence is presented that the superconductivity of La2 Srβ CuO4 and La2CuO4 occurs via holes in the LaO planes, rather than in the CuO2 planes.  相似文献   

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构造了具有Uqp(U3)Uqp(U2)Uqp(SO2)对称的双参数qp-形变二维相互作用玻色子模型(IBM),并给出了其能谱和跃迁矩阵元.结果表明,能谱和跃迁矩阵元极其敏感地依赖于第二个形变参数.  相似文献   

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Bi1.6Pb0.4Sr2—xMxCa2Cu3Oy(M=Mg,Ba)氧化物超导体   总被引:1,自引:0,他引:1  
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利用同位素间 Eliashberg 函数的关系及 Eliashberg 方程,我们计算了 La_(1.85)Sr_(0.15)CuO_4对应于~(16)O 及~(18)O 的 T_c,从而得到同位素指数α的值.计算结果与不同实验进行了比较.传统的电声机制可以解释这个同位素效应.  相似文献   

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We investigate the high resolution absorption spectroscopy of P2 radical, generated in ac glow discharge of PC13 buffered with helium, using optical heterodyne magnetic rotation enhanced concentration modulation spectroscopy in the visible region. The (1, 2), (1, 3) and (2, 3) bands of c^3Ⅱu- b^3Ⅱg in the range 16620-17860cm^-1 are observed and their 3II2 3II2 subbands are rotationally analysed. A set of effective molecular constants for the Ω= 2 component of the states involved are determined.  相似文献   

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本文以Sr(NO32和水为原料,采用水热法合成了一种新型的Sr(NO32结构。利用X-射线单晶衍射对其结构进行了测定,结果表明:该晶体属于立方晶系,Pa-3空间群,α=b=c=0.77402(7)nm,α=β=γ=90.00°,V=0.46372(7)nm3,Z=4,Dc=3.031g/cm3,F(000)=400,Rgt(F)=0.0287,wRref(F2)=0.0888。  相似文献   

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Lead strontium titanate (Pb0.50Sr0.50)TiO3 (PST) ceramics are prepared by the traditional ceramic processing. The dielectric constants and dielectric loss have been investigated in a temperature range from 25℃ to 300℃. The maximum dielectric constants for unpoled and poled samples are 9924 and 9683, respectively. The temperatures of phase transition for unpoled and poled samples are observed at 153℃ and 157℃, respectively. The phasetransition temperatures for unpoled and poled samples are not equal, which results from the polarization state of the domains. The remnant polarization and the coercive electric field are 18 uC/cm^2 and 6 kV/cm, respectively, from polarization-electric field (P - E) hysteresis loop. The temperature dependence of pyroelectric coefficients of the PST ceramics is measured by a dynamic technique. The dielectric constant and loss Lan δ of the poled PST ceramics are 813 and 0.010, respectively. The pyroelectric coefficients and figure of merit are 294 uC/cm^2 K and 13.6 × 10^-6 pa^-0.5, respectively, at room temperature 25℃and frequency lOOHz.  相似文献   

20.
《光谱实验室》2002,19(2):153-156
本文通过对[Fe 3O(Ala) 6(H 2O) 3](ClO 4) 7和[Fe 3O(Gly) 6(H 2O) 3](NO 3) 7·3H 2O的ESR谱的解析及变温磁化率的研究,得出它们的ESR谱具有各向同性的特点;朗德因子分别为2.019和1.997;两种配合物中铁离子间有反铁磁相互作用.  相似文献   

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