EDTA络合溶胶-凝胶法制备Y2O3:Eu纳米晶

以金属硝酸盐和EDTA为原料,用EDTA络合溶胶-凝胶法制备出Y₂O₃:Eu纳米晶,并对合成条件进行了优化.分别用TG-DTA、FTIR、XRD、SEM、荧光分光光度计等手段对凝胶的热分解机理,Y₂O₃:Eu的形成过程以及纳米晶的性质进行了研究.结果表明:硝酸根离子可以加速EDTA凝胶的热分解,仅在600℃焙烧即可得到颗粒细小、组分均匀,纯立方相的’Y₂O₃:Eu纳米晶,颗粒基本呈球形,粒径随温度升高逐渐长大,600℃时,约为20nm,1000℃时,约为70nm.     

热分解法合成Y2O3∶Eu3+纳米球及红色荧光性质研究

用热分解法在油酸和油胺混合溶剂中,320℃条件下,反应3h,成功制备了Y2O3:Eu3+纳米球。透射显微镜(SEM)和X粉末衍射仪(XRD)表征结果表明,成功合成了尺寸大约为15nm的Y2O3:Eu3+纳米球,JCPDS号为82-2415。且在紫外灯照射下,溶解于环己烷中的Y2O3:Eu3+纳米晶发射出比较强的红光,从荧光发射光谱上发现,发射峰的位置为594nm、614nm、628nm和709nm,分别对应Eu3+离子的5 D0→7F1,5 D0→7F2和5 D0→7F4跃迁。     

Y2O3∶Eu$1纳米晶的尺寸调控与发光性能研究

以尿素为沉淀剂,柠檬酸为表面活性剂,通过水热法得到了非晶态的水合硝酸氧钇前驱体,进一步烧结处理后生成了立方相Y2 O3纳米晶．利用X－射线衍射（ XRD）、扫描电镜（ SEM）、透射电镜（ TEM）、红外光谱（ FTIR）和荧光光谱（ PL）分别对所得样品的相结构、形貌粒度、表面结构以及发光性能进行研究．结果表明：当烧结温度从600℃升高到900℃,Y2 O3∶Eu3＋纳米颗粒的结晶性增强,并实现了粒径调控,由13．0 nm增加至27．9 nm．随着Y2 O3∶Eu3＋纳米颗粒尺寸的增加,比表面积减小会导致发光离子附近的表面晶格缺陷降低,同时纳米晶表面吸附水、硝酸根以及柠檬酸根等杂质离子逐渐被去除,减少了荧光猝灭中心,从而有利于增强荧光发射强度以及延长荧光寿命．     

纳米Y2O3:Eu3+粉体的表面包膜处理

本文采用高分子网络凝胶法制备了粒径约为20nm的纳米Y2O3:Eu3+粉体,并采用KAl(SO4)2及Na2SiO3溶液进行表面包膜处理,在纳米Y2O3:Eu3+粉体表面获得了约2nm厚的复合氧化物膜,发现包膜处理对纳米Y2O3:Eu3+粉体分散性能及表面结构有明显的影响.     

柠檬酸溶胶-凝胶法制备纳米Y_2O_3:Eu~(3+)粉体

以Eu2O3,Y2O3为原料通过柠檬酸溶胶-凝胶法合成了Y2O3:Eu3+纳米粉,研究了pH值、柠檬酸用量(n[H3Cit]:n[Y3++Eu3+])及煅烧温度对粉体制备过程的影响。利用TG-DTA、XRD、SEM等测试手段对粉体的形成过程进行了分析。结果表明:Y2O3:Eu3+纳米粉体的一次粒径为25nm左右,二次粒径为250nm左右。纳米Y2O3:Eu3+粉体制备最佳实验条件为pH=5,n[H3Cit]:n[Y3++Eu3+]为2:1,煅烧温度为600℃。     

纳米Ln2O3:Eu(Ln=Gd,Y)荧光粉的燃烧法合成及其光致发光性质

本文报道了用燃烧法制备的纳米（5～100nm）Gd2O3：Eu和Y2O3：Eu荧光粉，对它们的晶体结构和光致发光性质进行了研究．结果表明，纳米Gd2O3：Eu和Y2O3：Eu的光致发光性质与常规的Gd2O3：Eu和Y2O3：Eu的性质有很大的差别，纳米Gd2O3：Eu和Y2O3：Eu表现出很强的介观效应．对实验结果进行了初步的探讨．     

掺铕氧化钇发光纳米晶的拉曼光谱研究

采用凝胶燃烧法制备了8～50nm的Y2O3:Eu3+纳米晶.利用XRD确定了纳米晶的结构及晶粒大小,测定了不同晶粒大小的纳米晶Y2O3:Eu3+的拉曼光谱.通过测定不同的激发光所激发的拉曼光谱,以及比对荧光谱,指认了纳米晶Y2O3:Eu3+的Raman振动光谱,并且观察和研究了Raman光谱随晶粒尺寸的变化,发现了低维材料的一些反常拉曼效应.     

Y2O3:Eu3+纳米晶的制备及其光学性能研究

以NaOH,Y(NO3)3.6H2O和Eu(NO3)3.6H2O为前驱体,通过添加络合剂PEG-2000,采用水热法,成功地合成了Y2O3∶Eu3+纳米棒和纳米管,并采用先进的测试手段对其结构和性能进行了表征与测试。探讨了Y2O3∶Eu3+纳米棒和纳米管的生长机制,同时研究了Y2O3:Eu3+纳米晶的光致发光性能。研究结果表明,水热温度、反应时间、NaOH的添加量和PEG-2000对产物形貌有着非常重要的影响,所制备的材料具有Eu3+的特征红光发射,并在Eu3+的掺杂量为5%(摩尔分数)时样品发光最好。     

纳米NiFe2O4的制备及其对高氯酸铵的热分解催化性能

采用水热法制备出纯相的NiFe2O4纳米颗粒。利用X射线衍射仪(XRD),透射电镜(TEM)和傅里叶变换红外光谱仪(FT-IR)对样品进行了表征,并运用热分析法和质谱仪研究了样品对高氯酸铵的热分解催化性能。结果表明,制备的NiFe2O4纳米颗粒粒径约为5.0nm,对高氯酸铵的热分解具有很高的催化活性。当NiFe2O4纳米颗粒的添加量达到10%时,对高氯酸铵的热分解催化性能最好,可使高氯酸铵的高温分解温度降低89.8℃。     

Ca4Y6(SiO4)6O∶Eu纳米晶与微米晶发光对比研究

通过控制实验条件,合成了Ca4Y6(SiO4)6O∶Eu纳米晶和微米晶,经1000℃灼烧后,纳米晶的粒径约为50nm,提高灼烧温度并延长灼烧时间,可使其粒径达到几百个纳米.研究了纳米晶Ca4Y6(SiO4)6O∶Eu的发光特性,发光强度与灼烧温度的关系,灼烧温度及材料制备方法对Eu3+在Ca4Y6(SiO4)6O中的猝灭浓度的影响,并发现纳米晶的激发光谱中,Eu3+-O2-电荷迁移带蓝移的特性.     

Magnetic coupling in La0.67Ca0.33MnO3/La0.67Sr0.33CoO3/La0.67Ca0.33MnO3 sandwiches

La_0.67Ca_0.33MnO₃ (LCMO)/La_0.67Sr_0.33CoO₃ (LSCO)/LCMO trilayer films are fabricated on single-crystal substrates NdGaO₃ (110) and the interlayer coupling are investigated. Compared with LCMO single layer, sandwiches showed the enhanced metal-insulator transition temperature of LCMO layers. The magnetoresistance is dependent on spacer thickness and the peak value dramatically decreases when LSCO layer is thick enough because of shorting by the LSCO layer. The magnetic coercivity H_C shows a nonmonotonic behavior with changing spacer layer thickness and the waist-like hysteresis indicates that there is an indirect exchange coupling between the top and bottom LCMO layers across the spacer layer.     

Varistor properties of ZnO-Pr6O11-CoO-Cr2O3-Y2O3-In2O3 ceramics

The varistor properties of the ZnO-Pr₆O₁₁-CoO-Cr₂O₃-Y₂O₃-In₂O₃ ceramics were investigated for different concentrations of In₂O₃. The increase of In₂O₃ concentration slightly increased the sintered density (5.60-5.63 g/cm³) and slightly decreased the average grain size (3.4-2.9 μm). The breakdown field increased from 6023 to 14822 V/cm with increasing concentration of In₂O₃. The nonlinear coefficient increased from 17.6 to 44.6 for up to 0.005 mol%, whereas the further doping caused it to decrease to 36.8. In₂O₃ acted as an acceptor due to the donor concentration, which decreases in the range of 1.02 × 10¹⁷ to 0.24 × 10¹⁷/cm³ with increasing concentration of In₂O₃.     

Microstructures of YBa2Cu3O7/La0.7Ca0.3MnO3 and La0.7Ca0.3MnO3/YBa2Cu3O7 bi-layers grown on (001)LaAlO3

Epitaxial YBa₂Cu₃O₇/La_0.7Ca_0.3MnO₃ (YBCO/LCMO) bi-layers and La_0.7Ca_0.3MnO₃/YBa₂Cu₃O₇ (LCMO/YBCO) bi-layers were grown on (001)LaAlO₃ by pulsed laser deposition, and their microstructures were compared by transmission electron microscopy investigation. In the YBCO(100 nm)/LCMO(150 nm) bi-layers, the LCMO layer consists of columnar grains of ~ 17 nm in diameter and contains mixed orientation domains of [100]_c, [010]_c and [001]_c. The YBCO layer is totally c-axis oriented and the YBCO lattices are tilted − 2.5° to + 2.5° as they grew on the rough surfaces of LCMO columnar grains. For the LCMO(140 nm)/YBCO(140 nm) bi-layers, the LCMO/YBCO interface is sharp and flat. The initial 12-nm thickness of the YBCO layer is composed of c-axis oriented domains, and the upper part of YBCO layer is [100] oriented. The LCMO layer was predominantly [001]_c oriented while [100]_c-oriented domains were occasionally observed.     

Syntheses of hollandite type Rb2Cr8O16, K2Cr2V6O16 and K2V8O16

Hollandite-type compounds, Rb₂Cr₈O₁₆, K₂Cr₂V₆O₁₆ and K₂V₈O₁₆, were synthesized under high P-T conditions up to 1200°C and 7GPa. The structural refinement using a single crystal of Rb₂Cr₈O₁₆ confirms that the structure is similar to that of K₂Cr₈O₁₆. Magnetic measurements indicate that Rb₂Cr₈O₁₆ is ferromagnetic below 295K, K₂Cr₂V₆O₁₆ paramagnetic down to 77K and K₂V₈O₁₆ has susceptibility anomaly at 175K. These compounds are all semiconductive and show discontinuities in temperature-resistivity curves at points corresponding to magnetic anomalies.     

Nanocrystallization of SrBi2Nb2O9 from glasses in the system Li2B4O7---SrO---Bi2O3---Nb2O5

Transparent glasses in the system (100−x)Li₂B₄O₇–x(SrO---Bi₂O₃---Nb₂O₅) (10≤x≤60) (in molar ratio) were fabricated by a conventional melt-quenching technique. Amorphous and glassy characteristics of the as-quenched samples were established via X-ray powder diffraction (XRD) and differential thermal analyses (DTA) respectively. Glass–ceramics embedded with strontium bismuth niobate, SrBi₂Nb₂O₉ (SBN) nanocrystals were produced by heat-treating the as-quenched glasses at temperatures higher than 500 °C. Perovskite SBN phase formation through an intermediate fluorite phase in the glass matrix was confirmed by XRD and transmission electron microscopy (TEM). Infrared and Raman spectroscopic studies corroborate the observation of fluorite phase formation. The dielectric constant (_r) and the loss factor (D) for the lithium borate, Li₂B₄O₇ (LBO) glass comprising randomly oriented SBN nanocrystals were determined and compared with those predicted based on the various dielectric mixture rule formalism. The dielectric constant was found to increase with increasing SBN content in LBO glass matrix.     

PbSbBiS4-Sb2S3 and PbSbBiS4-Bi2S3 joins in the PbS-Sb2S3-Bi2S3 system

Phase equilibria along the PbSbBiS₄-Sb₂S₃ and PbSbBiS₄-Bi₂S₃ joins of the PbS-Sb₂S₃-Bi₂S₃ system have been studied for the first time using differential thermal analysis, X-ray diffraction, microstructural analysis, microhardness tests, and density measurements, and the phase diagrams of the joins have been mapped out. The joins are shown to be pseudobinary with limited series of terminal solid solutions. The solid solutions are p-type semiconductors.     

Structural study of Sr0.3Ba0.7Nb2O6 and La0.030Sr0.255Ba0.700Nb2O6 ceramic systems

Sr_0.3Ba_0.7Nb₂O₆ (SBN) and La_0.030Sr_0.255Ba_0.700Nb₂O₆ (LSBN) ceramic compounds have been prepared using the traditional ceramic method at two different calcination temperatures (900 and 1000 °C) and later sintered both at 1400 °C. A study of the effects of the calcination temperatures and La substitution on the morphological, compositional, and structural properties of SBN and LSBN is presented using scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. From Rietveld refinement processes, the XRD patterns were interpreted to evaluate such effects in the structural parameters and the site occupation factors of the heavy metals and oxygen atoms. The effect of the incorporation of La resulted in a 0.25% cell contraction and turned out to be higher than the 0.08% dilation effect produced by the increase of calcination temperature. The La ion with similar effective ionic radius and higher electronegativity is incorporated into the structure occupying the A₁ site just like the Sr ions in the SBN compound. Differences in the site occupation factors between the SBN and LSBN samples lead to substantial changes in the physical properties such as temperature of relative dielectric constant maximum, relative dielectric constant, and dielectric loss, correlated with the distortion and the relative orientation of the oxygen octahedra.     

静电纺丝法制备的Co0.6Ni0.3Cu0.1Fe2O4和Co0.6Ni0.3Zn0.1Fe2O4纳米纤维的结构及磁性能

采用静电纺丝技术制备出表面光滑、直径均匀的Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4/PVP和Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4/PVP纳米纤维前驱丝,经500~900℃煅烧后得到Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4和Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4纳米纤维。用TG-DSC、XRD、SEM及VSM现代测试分析手段对Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4和Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4纳米纤维的结构、形貌及磁学性能进行测试表征。结果表明:在空气气氛中经500~900℃煅烧后可得到纯尖晶石相、结晶度良好的纳米纤维或短纤维;当温度为700℃时,Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4和Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4纳米纤维的形貌细长而光滑且直径相对均匀,大约为80nm;此时Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4纳米纤维则保有较高的剩磁比(M_r/M_s)及矫顽力,分别为0.56和1 088.87Oe。在500℃、600℃、700℃、800℃、900℃煅烧后,Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4纳米纤维的饱和磁化强度分别比Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4纳米纤维增大了14.5%、7%、16%、10.7%、8%,而矫顽力则分别降低了38%、51%、50%、46%、46.7%。两种纳米纤维的饱和磁化强度及矫顽力存在差异,为CoNi铁氧体在电磁方面的应用提供了很好的参考。     

Vapour-liquid equilibria in the ternary mixtures N2---CH4---C2H6 and N2---C2H6---C3H8

A systematic study was performed with mixtures consisting of N₂, CH₄, C₂H₆ and C₃H₈, to investigate experimentally phase equilibria and caloric properties and to test the accuracy of thermodynamic correlations. The first part of this Paper reports results of T---p---x---y measurements on ternary systems in the range 20 < p < 120 bar and 140 < T < 220 K. The results are compared with data calculated by generalized equations of state.     

The effect of Bi1.5Zn0.5Nb0.5Ti1.5O7 cover layer on the dielectric and tunable properties of Ba0.6Sr0.4TiO3/Bi1.5Zn0.5Nb0.5Ti1.5O7 bilayered thin films

Bi_1.5Zn_0.5Nb_0.5Ti_1.5O₇ (BZNT) thin films with different thicknesses as cover layers were deposited on the Ba_0.6Sr_0.4TiO₃ (BST) thin films on the Pt/Ti/SiO₂/Si substrates by radio frequency magnetron sputtering method. The microstructure, surface morphology, dielectric and tunable properties of BST/BZNT heterogeneous bilayered films were investigated as a function of the thickness of BZNT films and the effect of BZNT films on the asymmetric electrical properties of BST/BZNT bilayered films was discussed. It was found that BZNT cover layer significantly improved the leakage current and the dielectric loss, and the dielectric constant and tunability of BST/BZNT bilayered thin films simultaneously decreased with the increasing thickness of BZNT films. The BST/BZNT bilayered thin film with a 50 nm BZNT cover layer gave the largest figure of merit (FOM) of 33.48 with the upper tunability of 55.38%. The asymmetric electrical behavior of BST/BZNT bilayered films is probably related to an internal electric field caused by built-in voltages at Pt/BST and BZNT/Au interfaces.