Er^3＋掺杂浓度对掺Er^3＋：TiO2粉末结构及其光致发光特性的影响

以钛酸正丁酯为前驱体，乙酰丙酮为络合剂，70℃下进行对前驱体改性的络合反应，获得改性前驱体Ti（O-Bu）4-x（AcAc）x．以异丙醇为溶剂，采用溶胶-凝胶（sol-gel）法制备0-3％（摩尔分数）Er^3＋掺杂TiO2粉末。差热-热重（DTA-TG）分析结果表明，掺1％（摩尔分数）Er^3＋：TiO2干凝胶粉末在烧结过程中，130-300℃之间出现两个放热峰，其余试样只出现一个放热峰，决定这一现象的结构因素同时也决定了材料中Er^3＋相对较高的分散度,X射线衍射（XRD）分析表明，700℃烧结所得的掺0-3％（摩尔分数）Er^3＋：TiO2粉末，当Er^3＋掺杂浓度为0．1％（摩尔分数）和1％（摩尔分数）时，粉末均为锐钛矿与金红石混合相，前者的金红石相衍射峰更明显；掺3％（摩尔分数）Er^3＋：TiO2粉末为单一锐钛矿相结构,700℃烧结，当Er^3＋掺杂浓度在0-1％（摩尔分数）范围内时，粉末PL强度随Er^3＋掺杂浓度提高而增强；继续增加Er^3＋掺杂浓度至3％（摩尔分数）过程中，粉末PL强度明显减弱。     

Y3+共掺杂对掺 Er3+: Al2O3粉末光致发光的增强作用

采用非水性溶胶-凝胶法制备了Y^3＋共掺杂的掺Er^3＋：Al2O3粉末，Er^3＋浓度为0．1和1．0mol％，Er^3＋和Y^3＋浓度比为1：0-10．X射线衍射和光致发光（PL）光谱结果表明：900℃烧结的掺0．1和1．0mol％Er^3＋：Al2O3粉末为具有非晶化特征的γ和θ混合相结构，非晶化趋势随Y^3＋共掺杂浓度增大而增加．掺0．1mol％Er^3＋：Al2O3粉末，PL光谱强度和半高宽随掺Y^3＋浓度增大无明显变化．掺1．0mol％Er^3＋：Al2O3粉末，PL光谱强度和半高宽随掺Y^3＋浓度增大而增加，10mol％Y^3＋共掺杂粉末的发光强度提高50倍，约为掺0．1m01％Er^3＋：Al2O3粉末的10倍，半高宽从77nm增至92nm．Y^3＋共掺杂对较高浓度掺Er^3＋：Al2O3粉末PL性能的增强作用归因于Y^3＋对Er^3＋在基体中的分散和配位结构多样性的提高．     

掺Er3+勃姆石(γ-AlOOH)凝胶高温烧结相变

采用溶胶-凝胶法(sol—gel)制备掺0-20mol％Er^3 勃姆石(γ-AlOOH)凝胶，X射线衍射和差热分析法研究掺Er^3 ：γ—AlOOH凝胶在950-1400℃烧结的相变过程．结果表明：Er^3 的掺杂降低α相的生长速度，抑制Al2O3的θ→α相变，推迟相变结束温度50-70℃，Er-Al-O系化合物Al10Er6O24和ErAlO3相的析出取决于掺Er^3 浓度和烧结温度．在较高烧结温度下，ErAlO3相由掺1-5mol％Er^3 ：Al2O3中析出；Al10Er6O24相则在掺5-20mol％Er^3 ：Al2O3中析出，随着烧结温度的升高，在全部掺Er^3 ：Al2O3中析出．ErAlO3相促进θ→α相变的形核，α相形核起始温度可提前30-50℃，但对α相生长影响不大．Al10Er6O24相对θ→α相变没有显著影响．     

镁掺杂对二氧化钛晶化行为的影响

采用溶胶-凝胶法在较低的热处理温度下制备了镁掺杂的TiO2。通过差热分析（DTA）并经过计算，发现在TiO2溶胶中加入Mg（NO3）2，可以让TiO2从无定型到锐钛矿相和锐钛矿相到金红石相的晶型转变活化能分别从137．7和163．7kJ／mol降低到70．5和108．4kJ／mol；采用X射线衍射分析（XRD），确定了在600℃热处理，获得了具有锐钛矿相和金红石相混晶的镁掺杂TiO2；通过紫外光催化降解甲基橙水溶液实验，证明了镁掺杂的TiO2薄膜的光催化活性高于未掺杂TiO2薄膜。     

水热合成法制备锐钛矿型纳米TiO2粉体的研究

以工业硫酸氧钛为原料，尿素作沉淀剂，固定6MPa的初始压力和300r／min的搅拌速度，在110-150℃的反应温度、2-8h的反应时间、0．25-1．5mol／L的硫酸氧钛反应浓度的条件下，采用水热合成法制备了锐钛矿型纳米TiO2粉体．采用XRD、TEM、BET等测试手段对在不同条件下所制备粉体的物相组成、晶粒度、比表面积等进行了分析．结果表明，所制备的粉体均为锐钛矿型纳米TiO2．粉体的比表面积分布在124-240m^2／g、晶粒度分布在6．7-10．6nm．随着反应温度的升高和反应时间的延长，晶粒度增大，比表面积降低．随前驱体浓度的提高，晶粒度也增大，当前驱体浓度〈0．5mol／L时，比表面积随着前驱体浓度的增大而增大．当前驱体浓度〉0．5mol／L时，比表面积随着前驱体浓度的增大而减少．     

柠檬酸-硝酸盐燃烧法制备Ba0.5Sr0.5TiO3介电材料

以硝酸钡、硝酸锶，钛酸四丁脂以及氨水为原料，利用柠檬酸-硝酸盐燃烧法制备了Ba0.5Sr0.5TiO3(BST)超细粉末．详细研究了pH值、分散剂对形成BST粉末粒度的影响．用所合成的粉末压片，1300℃烧结2h即可获得致密烧结体，烧结样品的平均粒径约为1μm．在10kHz，25℃下的介电性能为：介电常数1470，介电损耗0．006．     

高热稳定性锐钛矿型TiO2纳米粉体的制备

采用醇盐在有机溶剂中高温热水解与结晶同时进行的方法，制备了锐钛矿型TiO2纳米粉体．以XRD、BET、TEM、TG和DTA等方法对获得的粉体进行了表征．所制得的纳米粉体能在很宽的温度范围（200～700℃）内保持锐钛矿型晶体结构．经550℃煅烧所得的TiO2纳米粉体，平均粒径为14nm，比表面积在100m2／g以上．     

钛酸盐一维纳米材料向TiO2纳米材料的水热转化研究

采用强碱性水热处理法分别控制第一次水热反应为160℃和200℃,制备出一维纳米管和纳米棒2种形貌的产物,将其作为第二次水热反应的前驱体,考察了第二次水热体系中pH值和温度对TiO2纳米材料的晶相组成及其微观形貌的影响;采用XRD、TEM以及HRTEM对样品进行了分析.结果表明,当以纳米管为前驱体时,除在pH=0的体系中得到了以金红石相为主的单晶纳米棒外,在pH值为2、4和7的条件下均得到了单晶纯锐钛矿相TiO2纳米颗粒.当以纳米棒为前驱体时,在pH=0的体系中得到了金红石相与板钛矿相共存的纳米棒和纳米颗粒混合产物;在pH值为2、4和7的条件下均得到了纯锐钛矿相TiO2纳米棒;当二次水热温度低于180℃时,前驱体没有转化完全,所得产物为前驱体与锐钛矿相TiO2共存的纳米棒;当水热温度为180℃和210℃时,产物为纯锐钛矿相纳米棒.     

脉冲电流烧结掺杂Ba0.5Sr0.5TiO3陶瓷介电性能的研究

以硝酸钡、硝酸锶、钛酸四丁脂、硝酸铜、硝酸镧以及氨水为原料，利用柠檬酸一硝酸盐燃烧法制备了Ba0．5Sr0．5TiO3(BST)、1mol％Cu^2 掺杂BST、1mol％La^3 掺杂BST，以及0．5mol％Cu^2 和0．5mol％La^3 共掺杂BST粉末．利用脉冲电流(简称PECS)烧结设备烧结所制备的粉体，结果发现掺杂可以大大改善BST陶瓷晶粒大小的均匀性．介电性能测试结果表明1mol％Cu^2 掺杂不仅降低了BST的介电损耗，同时也降低了介电常数，而1mol％La^3 掺杂，以及0．5mol％Cu^2 和0．5mol％La^3 共掺杂降低了BST的介电损耗，但在25℃附近介电常数升高．     

热处理对溶胶-凝胶TiO2薄膜的晶相转变和性能影响

以钛酸丁酯（TPOT）为有机醇盐前驱体，采用溶胶－凝胶技术制备了TiO2溶胶。为测量方便起见，分别制备了凝胶粉体和薄膜，并对样品进行了不同温度的热处理。X射线衍射（XRD）、椭偏仪和紫外－可见光谱（UV－vis)的测量表明：随热处理温度的升高，TiO2的结构由非晶到锐钛矿再到金红石相转变，400℃为锐钛矿相，600℃开始出现金红石相，800℃完全转变为金红石相；晶粒尺寸随热处理温度的升高而逐渐增大，锐钛矿结构的晶粒尺寸范围是2.5-5.5nm，金红石结构的晶粒尺寸范围是5.9-6.8nm；TiO2薄膜的折射率随热处理温度的升高而增大，同时薄膜厚度降低；禁带宽度随热处理温度的升高而增大，同时薄膜厚度降低；禁带宽度随热处理温度升高而变窄，锐钛矿结构的禁带宽度为3.45eV，而金红石结构的禁带宽度为3.30eV。     

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.     

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.     

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.     

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.     

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.     

MoO3-V2O5-P2O5-Fe2O3玻璃的制备及性能研究

制备了MoO3-V2O5-P2O5-Fe2O3系磷酸盐玻璃,研究了玻璃形成能力、热膨胀系数和抗潮解等性能.结果表明,MoO3-V2O5-P2O5-Fe2O3系统具有较宽的玻璃形成区和较强的玻璃形成能力,当MoO3/V2O5≈1.5时,玻璃形成能力最强.MoO3-V2O5-P2O5-Fe2O3玻璃的热膨胀系数约为60～110×10-7/℃,并且随着Fe2O3含量的增加而逐渐增大.加入适量的Fe2O3能够显著改善MoO3-V2O5-P2O5玻璃的抗潮解性能,在90℃的去离子水中的溶解速率达到8.0×10-9g·cm-2·min-1.     

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.     

MgO-Al2O3-SiO2-TiO2-Y2O3玻璃的弹性模量

根据硬盘基板用材料的要求，制备了MgO-Al2O3-SiO2-TiO2-Y2O3高弹性模量玻璃（120GPa)，玻璃的弹性模量随组成的变化服从Makishima-Mackenzie理论，MgO,Al2O3,TiO2,Y2O3等具有较高单位体积离解能的氧化物有利于提高玻璃的弹性模量，但玻璃弹性模量的理论计算值低于测试值，这是因为Makishima-Mackenzie理论没有考虑玻璃内阳离子的具体配位，对MgO,Y2O3堆积密度因子的堆导存在误差，因此利用Makishima-Mackenzie理论发展高弹性模量玻璃时应对MgO,Y2O3等氧化物的计算进行修正。