溶胶-凝胶法制备Li(MoO4)2:Eu及表征

用溶胶-凝胶法制备了平均粒径为2～3μm的小颗粒、高亮度的Li(2-x)(MoO4)2:Eux系列钼酸盐红色荧光体.用XRD、SEM、粒度分析和分子荧光光度计对荧光体进行了表征和研究.常规的固相反应合成Li(2-x)-(MoO4)2:Eux系列红色荧光粉需要在900℃以上的高温才能够形成均一的固溶体,而采用溶胶-凝胶法制取,在700℃就可以形成均一的单相Li(2-x)(MoO4)2:Eux,在750℃就可得到发光亮度最高的荧光体.其亮度是常规固相反应于900℃制得的荧光体的124%.采用溶胶-凝胶法制取Li(2-x)(MoO4)2:Eux系列,可以在相当宽的实验条件范围内得到小粒径、窄分布和高亮度的荧光体,具有良好的颗粒形貌.     

溶胶-凝胶法合成LED用红色发光材料R2-xEux（MoO4）3（R=Gd，Y，La）及性能研究

采用溶胶-凝胶法合成了发光二极管（LED）用R2-xEux（MoO4）3（R=Gd，YLa；0≤x≤2）系列高亮度红色荧光粉，并对其结构与发光性能进行了详细研究。采用粉末x射线衍射（XRD）测量了不同温度下合成的样品结构变化情况，发现当R=y和Gd时，它们具有单斜和正交两种结构：当R=La时，荧光粉只有一种单斜结构．同时用荧光光谱对它们的发光性能进行了研究，发现在相同条件下（相同温度，相同时间，相同浓度）得到的样品的发光强度顺序为La0.8Eu1.2（MoO4）3〉Gd0.8Eu1.2（MoO4）3〉Y0.8Eu1.2（MoO4）3，且它们在395和465nm均有较强的有效激发，这两种波长正好与商用的GaN基LED芯片相匹配,同时研究了煅烧温度及掺杂浓度对其发光性能的影响。     

Li1.3Al0.3Ti1.7(PO4)3的溶胶-凝胶法制备及其性质研究

采用溶胶凝胶法及固相反应法合成锂离子固体电解质Li1.3Al0.3Ti1.7(PO4)3,用X射线衍射检测合成产物的物相,用循环伏安及交流阻抗技术测试产物的电化学窗口及离子电导率等电化学性质。研究表明溶胶凝胶法合成的Li1.3Al0.3Ti1.7(PO4)3的电化学窗口为2.4V。与固相反应法相比,溶胶凝胶法合成的Li1.3Al0.3Ti1.7(PO4)3具有更好的结晶性,其烧结片具有较高的离子电导率和较小的活化能。     

白光LED用红色荧光粉的制备及性能研究

采用溶胶-凝胶法合成了可用于395 nm及465 nm激发的Ca1-2xBxEu MoO4 (B=Li+,Na+,K+)红色荧光粉.用XRD和荧光光谱对其结构、发光性能进行了表征,并就不同电荷补偿对其发光性能的影响进行了分析.同时研究了煅烧温度及Eu3+浓度对所得荧光粉发光性能的影响.     

白光LED用MMoO_4∶Eu~(3+)红色荧光粉制备工艺研究

用溶胶-凝胶优化法合成了红色荧光粉MMoO4∶Eu3+(M=Ca、Sr、Ba),通过SEM、PL表征了荧光粉的形貌及发光性能。结果表明:烧结温度为800℃时,颗粒粒度分布均匀,粒径约为0.5-1μm,有很好的分散性;掺杂0.25molEu2O3在395nm和464nm两主激发峰下,均可得到616nm处红光发射极峰,属于Eu3+典型的5 D0→7F2的跃迁所致;助熔剂NH4F明显提高了钼酸盐荧光粉的发光强度;通过比较M0.5MoO4∶Eu03.+25,Li0+.25(M=Ca、Sr、Ba)发光性能得知:在395nm激发下,Ca0.5MoO4∶Eu30.+25,Li0+.25荧光粉最有利于提高发光强度。     

绿色荧光材料YVO4：Er制备及其发光性能研究

以柠檬酸作为络合剂，采用溶胶-凝胶法制备了绿色荧光材料YVO4：Er，采用XRD、荧光光谱仪、SEM对产物的相组成、发光性能和颗粒形貌进行了分析和观测。结果表明，实验所得产物为单一的四方锆型YVO4：Er晶体；产物能够被200-320nm的紫外光激发，发出明亮的绿色荧光，前驱体在900℃焙烧、保温2h时，产物的发光性能最佳。     

Li2ZnSiO4溶胶-凝胶法合成及其离子导电性

用溶胶凝胶法制备了锂离子导体Li2ZnSiO4的纯相.实验结果表明,与传统固相制备方法相比,用这种方法可以使Li2ZnSiO4的生成温度降低,应用交流阻抗谱技术测定了样品烧结体的离子导电性.     

无机盐溶胶-凝胶工艺制备长余辉发光粉体的研究

以无机盐为原料,成功地制备了均一、稳定、透明的SrAl2O4溶胶.系统地研究了无机盐溶胶一凝胶工艺制备SrAl₂O₄:Eu²⁺,Dy³⁺长余辉发光粉体的工艺条件及其影响因素,并通过透射电镜和荧光光谱分析对粉体的微结构、表面形态及发光性能进行了表征.实验结果表明,在适宜的工艺条件下,可制备颗粒均匀的针状纳米发光粉体,其发光特性与传统的高温固相烧结法相似,但烧结温度可降低300℃左右.     

络合作用对Sol-gel法制备Er3+掺杂TiO2粉末光致发光特性影响

以钛酸正丁酯为前驱体，乙酰丙酮为络合剂，分别在室温和70℃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0．1—3．0mol％Er^3＋抖掺杂TiO2粉末．差热-热重（TG-DTA）分析结果表明，由室温络合改性前驱体制备的粉末，无定型到锐钛矿和锐钛矿到金红石的相变温度，较由70℃络合改性前驱体制备的粉末均升高40℃．X射线衍射（XRD）分析表明，700℃烧结，室温络合所得掺0．1-3．0mol％Er^3＋：TiO2粉末为单一锐钛矿结构，70℃络合所得粉末为锐钛矿和少量金红石的混合相结构．400-800℃烧结，两种络合所得粉末均获得中心波长为1．53μm的多峰结构光致发光（PL）谱．其中，700℃烧结的粉末PL强度最强．70℃络合较室温络合的粉末PL强度可提高3倍．     

新型特效Na离子吸附剂Li1+xAlxTi2-x(PO4)3的制备和性能研究

采用高温固相法合成了新型特效Na离子吸附剂Li1＋xAlxTi2-x（PO4）3．通过对不同条件下合成的样品XRD、SEM及其吸附性能的研究表明，少量Al的加入未影响到LiTi2（PO4）3的晶体结构，但使Li1＋xAlxTi2-x（PO4）3对Na离子产生了特效吸附作用．当x=0．4时，在pH值为10．0—11．0条件下，Li1＋xAlxTi2-x（PO4）3的吸附容量达到11．76mg／g．另外，本文对材料的激光拉曼光谱和红外光谱进行了研究和指认．     

VLE data for CO2-CF2Cl2, N2-CO2, N2-CF2Cl2 and N2-CO2-CF2Cl

Knowledge about vapour-liquid (VLE) is required as a basis of reliable calculations for separation processes. Correlations available for the prediction of T, p, x, y data are less accurate for mixtures at high pressures and mixtures containing supercritical components. The results of VLE experiments are reported and compared with data calculated with equations of state.     

Preparation of ZrO2-CeO2 and HfO2-CeO2 nanopowders

We prepared weakly agglomerated powders of ZrO₂-CeO₂ and HfO₂-CeO₂ solid solutions 5–8 nm in particle size, consisting of monoclinic and tetragonal phases. After heat treatment at 1200°C, the crystallite size was 30 and 14 nm, respectively. We also examined the effect of precipitate freeze drying on the crystallization of hafnia-based solid solutions containing up to 20 mol % CeO₂.     

Thermal diffusion in binary mixtures H2-CCl2F2 and H2-CHClF2

Thermal diffusion coefficients were measured in two gaseous mixtures, in which one component was close to the critical temperature, in the pressure range (19.6–127.4)·10⁴ N/m² and at a freon concentration of 0.25–0.8.     

Comparison of the Electronic Structures of La2CuO4, Sr2CuO2Cl2, and Sr2CuO2F2

First-principles cluster calculations are reported of the local electronic structure of the three compounds: La₂CuO₄, Sr₂CuO₂Cl₂, and Sr₂CuO₂F₂. The copper ${\text{3d}}_{x^2 - y^2 } $ and the planar oxygen 2p _σ atomic orbitals exhibit a similar degree of covalency. The out-of-plane orbitals, however, are quite different with the ${\text{3}}d_{3z^2 - r^2 } $ atomic orbital lowered significantly in energy for chlorine and fluorine apical positions.     

Radial GRIN glasses in Li2O-Na2O-Al2O3-TiO2-SiO2 systems

A series of GRIN glass rods have been developed in Li2O-Na2O-Al2O3-TiO2-SiO2 systems. Negative radial refractive index profiles were generated by exchanging Na+ for Li+ ions in these glass rods. It has been observed that TiO2 plays a vital role in increase in the profile depth and maximum change in the refractive index because of its ambivalent nature. Change in the refractive index can be further increased by increasing the concentration of exchanging cation in the base glass.     

Thermoelectric power of single-phase samples of Tl2CaBa2Cu2O y and Ba2CaSr2Cu2O y

Single-phase 2122 samples of thallium and bismuth superconductors were made by the precursor matrix method. The thermopower of these samples was measured in the temperature range 250 K-T _c . The thermopower was positive and decreased linearly with increasing temperature aboveT _c (onset). The exponential enhancement of thermopower seen in the undoped and doped YBCO was not observed in these samples. The linear variation of thermopower can be explained on the basis of either a two-band model or a narrow band model.     

Si_2N_2O-Al_2O_3-La_2O_3和Si_2N_2O-Al_2O_3-CaO系统的亚固相关系

本文给出了 Si_2N_2O-Al_2O_3-La_2O_3和 Si_2N_2O-Al_2O_3-CaO 系统的亚固相图。实验结果表明:在 Si_2N_2O-Al_2O_3-CaO 系统中有一个未知结构的新化合物 CaO·Si_2N_2O,在3CaO·Si_2N_2O 和3CaO·Al_2O_3两化合物之间形成连续立方固溶体。而 Si_2N_2O-Al_2O_3-La_2O_3系统中则没有发现新化合物。在两个系统的富 Si_2N_2O区,过量的 Si_2N_2O 与 La_2O_3和 CaO 分别反应形成 Si_3N_4与 La_(10)[SiO_4]_(?)N_2(H-相)(和 CaSiO_3。所研究的这两个三元系统中,分别形成了如下几个四元相容性区。在 Si_2N_2O-Al_2O_3-La_2O_3系统内有:H-Si_3N_4-La_2O_3·Si_2N_2O-La_2O_3·Al_2O_3;H-Si_3N_4-La_2O_3·Al_2O_3-La_2O_3·11 Al_2O_3;H-Si_3N_4-La_2O_3·11 Al_2O_3-Al_2O_3;H-Si_3N_4-Al_2O_3-O′s.s;H-Si_3N_4-O′s.s-Si_2N_2O在 Si_2N_2O-Al_2O_3-CaO 系统内有:Si_3N_4-CaSiO_3-CaO·Si_2N_2O-3CaO·Al_2O_3;Si_3N_3-CaSiO_3-3CaO·Al_2O_3-2CaO·Al_2O_3·SiO_(?);Si_(?)N_(?)-CaSiO_3-2CaO·Al_2O_3·SiO_2-Al_2O_3;Si_3N_4-CaSiO_3-Al_2O_(?)-O′s.s;Si_3N_4-CaSiO_3-O′s.s-Si_(?)N_(?)O     

Elastic and Electronic Properties of Superconducting CaPd 2 As 2 and SrPd 2 As 2 vs. Non-superconducting BaPd 2 As 2

The first-principles calculations were performed to predict the elastic and electronic properties of the superconducting ThCr₂Si₂-type phases CaPd₂As₂ and SrPd₂As₂ in comparison with the non-superconducting CeMg₂Si₂-type phase BaPd₂As₂. Besides, the same properties were compared for CeMg₂Si₂- and ThCr₂Si₂-type polymorphs of BaPd₂As₂. We found that all these phases are mechanically stable and belong to soft materials with low hardness. The near-Fermi region is formed by the valence states of the blocks [Pd₂As₂] with decisive contributions of Pd 4d states. The values of N(E _F) increase in the sequence: CaPd₂As₂ < SrPd₂As₂ < BaPd₂As₂, i.e. in the reverse sequence relative to the transition temperatures T _C. Thus, the change in T _C cannot be explained by the electronic factor, i.e. by the simple correlation T _C～N(E _F). Most likely the decrease in T _C in the sequence CaPd₂As₂ → SrPd₂As₂ and the absence of a superconducting transition in BaPd₂As₂ are related to the structural factors and the peculiarities of the electron–phonon coupling mechanism.