Mn2+掺杂Ba2LuF7纳米晶的制备以及发光颜色调控

通过水热法合成了Yb和Tm共掺的Ba2LuF7纳米晶。合成出的样品用透射电镜(TEM)和X射线粉末衍射仪(XRD)进行了表征。在980nm激光下测试了样品的发射光谱。结果表明纳米晶属于立方晶相,大小只有10~20nm。适当的稀土离子掺杂,可使样品发出较强的绿光和红光。通过在纳米晶中掺杂锰离子(Mn2+),可以调控绿光和红光的强度。此外锰离子(Mn2+)掺杂也会影响纳米晶的晶相和尺寸。当加入的Mn2+浓度较高时,会出现新的晶相,样品的形貌和尺寸也有显著的变化。     

Mn2+掺杂对V2O5纳米材料结构与电化学性能的影响

以V2O5粉末、H2O2和Mn(CH3COO)2·4H2O为原料,采用水热法制备了纳米结构的锂离子电池阴极材料Mnx V2O5。运用X射线衍射(XRD)、X射线光电子能谱分析(XPS)和扫描电镜(SEM)测试对制备的材料进行结构和形貌表征,并利用充放电测试和交流阻抗测试研究了样品的电化学性能。结果表明:随着锰掺杂量的增加,V2O5的正交晶型层状结构未发生改变,其层间距逐渐扩大,形貌由纳米短棒状向纳米带簇状变化。电化学测试表明:Mn2+掺杂提高了V2O5的电化学性能,其首次充放电效率由70.8%提高到90%以上;Mn0.01V2O5经过90次充放电循环后,其容量仍为192.2 mAh/g。Mn2+掺杂对V2O5电极材料的离子电导率有影响,Mn0.02V2O5离子电导率由未掺杂时的6.27×10-4S/cm提高到1.58×10-3S/cm。     

Ce3+、Mn2+掺杂Zn3（BO3）2的制备及其发光性能

采用共沉淀法在700℃和较短的烧结时间下制备了Zn3(BO3)2和不同浓度的Ce3+、Mn2+离子掺杂的Zn3(BO3)2纳米晶粉末,对合成产物的发光性质及发光机理进行了研究。利用荧光分光光度计、X射线粉末衍射仪以及透射电镜对其光学性能和纳米晶形貌进行了表征。结果表明Ce3+离子掺杂的Zn3(BO3)2样品在340～400nm之间有强的荧光发射,其最高发射峰峰位为365nm,在Ce3+掺量为0.5%(摩尔分数,下同)时发光强度达到最高值。Ce3+取代Zn2+离子作为发光中心,Mn2+离子作为激活剂加入,并不影响荧光发射峰的位置,但能够有效增强其发光强度。当Mn2+离子掺量为0.7%(摩尔分数)时,Ce3+、Mn2+共掺杂的Zn3(BO3)2纳米晶发光强度达到最高值。     

Li0.97+δTi0.03Fe0.97Mn0.03 PO4/C复合材料的制备及其电化学性能研究

用共沉淀法合成Fe0.97Mn0.03PO4前驱体,再通过碳热还原法合成多元掺杂的Li0.97 δTi0.03Fe0.97Mn0.03PO4/C复合材料,利用X射线衍射(XRD),扫描电镜(SEM)、傅立叶红外光谱(FTIR)等测试手段对样品的晶体结构、表观形貌、谱学性质等进行了分析研究,对其倍率放电性能及循环性能等进行了测试,并与不掺杂的LiFePO4/C复合材料进行了比较.研究表明,掺杂过程中,掺杂的Mn4 、Ti4 离子能与LiFePO4形成单一的橄榄石型晶体结构,晶型完整,产物形貌规则,平均粒径在1um左右.用Li0.97 δTi0.03Fe0.97Mn0.03PO4/C为正极材料制作的电池分别以0.2,1,5、10C倍率放电,首次放电容量为134.0、133.4,130.1和127.2mAh·g-1,并表现出良好的循环性能.     

铝共掺杂调制ZnO∶Mn纳米棒阵列的磁学和电学特性

采用磁控溅射方法制备了锰掺杂氧化锌和铝、锰共掺杂氧化锌纳米棒阵列并详细研究了它们的电学和磁学特性。微结构测试的结果表明,掺杂后的氧化锌纳米棒阵列保持了纤锌矿晶体结构,掺杂锰离子和铝离子占据了晶体中锌离子的位置实现了替位式掺杂。磁学性质测试结果表明铝、锰共掺杂氧化锌纳米棒在室温下具有明显的铁磁性,饱和磁矩为0.33μB/Mn atom,是居里温度高于室温的一维稀磁半导体材料。电学性质测试结果表明铝的共掺杂可以使得锰掺杂氧化锌纳米棒的电阻率降低4个数量级,使得铝、锰共掺杂氧化锌纳米棒有可能在未来自旋电子器件中作为高效自旋注入元器件得到广泛应用。     

Si4+离子对Y3+:PbWO4晶体闪烁性能及辐照硬度的影响

Y3+离子掺杂钨酸铅晶体特殊的低剂量率辐照行为一般在晶体顶端表现更为明显,以往研究认为该现象起因于晶体中有效分凝系数<1的Na+、K+和Si4+等杂质在顶端的富集.本文研究了Si4+掺杂的Y3+:PWO晶体,对晶体顶端和晶种端的分段晶体测试了退火温度对晶体透过率和辐照硬度的影响,结果发现:在实验所涉及的掺杂浓度范围内,Si4+离子杂质对Y3+:PWO晶体的辐照硬度及透过率无影响,可以认为Y3+:PWO晶体特殊的低剂量率辐照行为和晶体中的Si4+离子含量无关.     

双元共掺杂Bi1-xLax(Fe0.95Mn0.05)O3多铁性材料的磁性研究

采用溶胶-凝胶法制备了Bi1-xLax(Fe0.95Mn0.05)O3(x=0,0.10,0.15)多晶样品。X射线衍射实验表明La、Mn离子共掺杂没有改变样品的四方晶格结构。X射线能量色散分析显示样品的化学组分几乎不变。Mn离子掺杂或者是(La、Mn)离子共掺杂,导致铁酸铋材料的磁性增强。X射线吸收精细结构实验表明Mn3+的局域结构的改变是样品磁性增强的原因。     

Ba0.8Sr0.2Ti0.5Mn0.5O3纳米晶体的合成及气敏性质研究

采用复合碱媒介法(CHM),在合成BaMnO3和Ba0.5Sr0.5MnO3的基础上,以Sr(NO3)2、BaCO3以及MnO2和TiO2为原料,在200℃、24h的生长条件下,用20%的Sr离子替代20%的Ba离子,用50%的Ti离子替代50%的Mn离子成功合成了Ba0.8Sr0.2Ti0.5Mn0.5O3纳米晶体。采用XRD、SEM及EDS对产物的晶相、形貌和成分进行了分析,对Ba0.8Sr0.2Ti0.5Mn0.5O3制作的电极进行了气敏性质的测定。     

掺杂锗酸铋晶体(Bi_4Ge_3O_(12))的电子顺磁共振

用电子顺磁共振方法对 Fe、Cr 和 Mn 杂质在 Bi_4Ge_3O_(12)晶体中的位置和价态进行了研究。测试并分析了和 Fe~(3+)和 Cr~(3+)离子的 EPR 谱线位置随磁场方向的变化,确定了 Fe~(3+)和 Cr~(3+)主要进入氧四面体占据 Ge位。测试并分析了 Mn~(4+)和Mn~(2+)掺杂样品各向异性的 EPR 谱线,也测试了处于晶体粉末态及玻璃态的 Mn 掺杂样品的谱线,认为 Mn~(2+)离子进入氧八面体占据 Bi 位。紫外线辐照后 Mn 离子 EPR 信号降低表明辐照导致 Mn 离子价态改变。     

高效Mn/ZnO-Ag纳米复合光催化体系的简易制备及研究

本研究使用简易高分子网络凝胶法制备了不同Mn含量掺杂的ZnO及Mn、Ag共掺的ZnO纳米光催化剂.在模拟太阳光下通过降解有机染料亚甲基蓝(MB)来研究样品的光催化性能.XRD和SEM证实,Mn的掺入减小了样品的晶粒尺寸,但改善了样品的颗粒分布.通过XPS能谱发现催化剂中存在Mn2+和Mn3+,且随Mn离子掺杂量的增加,Mn3+/Mn2+比例增大.PL光谱显示,Mn/ZnO-Ag体系的发光强度较纯ZnO显著降低,其中当Mn浓度为1％(摩尔分数)时展现出最高效的光生载流子分离.结果表明,Mn掺杂显著增强了ZnO对可见光的吸收,但在一阶光降解动力学方程中并未发现显著的光催化活性提升,而Mn/ZnO-Ag样品在保持较好光学性能的同时大幅提高了ZnO的光催化活性.结合光催化测试结果发现,Mn/ZnO-Ag样品光催化性能的提升与其对可见光利用率的提高、Mn离子间价态变化及Mn离子与Ag粒子间的协同作用有关.这为系统性提升ZnO的光催化活性提供了一种有用的途径.     

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.     

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.     

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.     

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.     

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.     

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.     

Characterization of YBa2Cu3O7/PrBa2Cu3O7 superlattices

We investigated the structural and superconducting properties ofc-axis oriented (YBa₂Cu₃O₇) _nY /(PrBa₂Cu₃O₇) _npr superlattices with thicknesses of the individual layers down to one unit cell (10nY1; 18>nPr 1). By transmission electron microscopy and X-ray diffraction we find an excellent structural quality of the samples, though the quantitative analysis shows the existence of defects. In superlattices with decoupled YBa₂Cu₃O₇ layers of two unit cell thickness we find a highT _c value of 75 K. We probed the flux line structure in the superlattices by measurements of the critical current density in magnetic fields. The experiments show that the flux-line dynamics is dominated by the movement of pancake vortices.     

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.     

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.