Enhanced thermal stability of zinc-based titanate (dielectric) ceramics prepared by the modified sol-gel route

A multi-component substitution of Co and Ni was incorporated into ZnTiO3 to form pure hexagonal Zn1-x(Co1/2Ni1/2)xTiO(3) (x = 0,0.8,0.9,1.0) dielectric ceramic powders by a modified sol-gel route, following heat treatments at 600 degrees C for 3 h and at 800 degrees C for 6 h. Differential scanning calorimetry measurements revealed that the order of increasing thermal stability of solid solution compound Zn1-x(Co1/2Ni1/2)(x)TiO3 was ZnTiO3 (945 degrees C), Zn0.1Ni0.9TiO3 (1346 degrees C), Zn-0.1(Co1/2Ni1/2)(0.9)TiO3 (1390 degrees C), and Zn0.1Co0.9TiO3 (> 1400 degrees C). Both the dielectric constant and loss tangent reached a maximum at x = 0.8 and then decreased with solubility, x, and measurement frequency.

离子型晶体的点电荷电量的确定和晶体的化学键性质MX(M=Mg,Ca,Sr,Ba,X=O,S,Se,Te;不含MgTe)

离子型晶体的点电荷电量的确定和晶体的化学键性质ＭＸ（Ｍ＝Ｍｇ，Ｃａ，Ｓｒ，Ｂａ，Ｘ＝Ｏ，Ｓ，Ｓｅ，Ｔｅ；不含ＭｇＴｅ）孟庆波武志坚张思远（中国科学院长春应用化学研究所稀土无机材料实验室，长春１３００２２）ＮｅｔＣｈａｒｇｅａｎｄＣｈｅｍｉｃａｌＢｏｎ...

NdSr_（1－x）M_xNiO_4（M＝Ca，Ba）的合成，结构和电学磁学性

用固相法首次合成了ＮｄＳｒ＿（１－ｘ）Ｍ＿ｘＮｉＯ＿４（Ｍ＝Ｃａ：０．０≤１．０；Ｍ＝Ｂａ：０．０≤ｘ≤０．６）系列复合氧化物，并研究了其结构，红外光谱，电学性质和磁学性质。除ＮｄＣａＮｉＯ以正交晶系结晶外，其它试样的结构均属于四方晶系。ＩＲ谱显示随Ｃａ￣（２＋）离子含量的增加，ＮｄＳｒ＿（１－ｘ）Ｍ＿ｘＮｉＯ＿４的Ｎｉ－Ｏ键缩短，Ｃａ￣（２＋）和Ｂａ￣（２＋）引入ＮｄＳｒＮｉＯ＿４以取代Ｓｒ￣（２＋），使试样由金属性导电转变为半导体性导电；随Ｃａ￣（２＋）含量增加，试样的室温电阻率增大。７７～３００Ｋ磁化率与温度关系曲线显示，所有试样的Ｎｉ￣（３＋）都以低自旋状态存在。

RE_(1-x)B_xF_(3-y)(RE=Y、La、Ce、Gd;B=Ca、Ba)的敏感性质的研究

LaF_3作为离子选择性电极和对气体的敏感性质已进行了一定的研究,但其他稀土氟化物的敏感性质却未见报道。本文合成了RE_(1-x)B_xF_(3-y),研究了它们的结构、电学性质及敏感性质,得到有可能在150℃使用的固体电解质氧敏材料。 (一) RE_(1-x)B_xF_(3-y)的结构分析 结构分析表明,Ca、Ba置换RE的含量少时,如La_(0.95)Ba_(0.05)F_(3-y)、Ce_(0.95)Ca_(0.05)F_(3-y)的X射线衍射分析结果与LaF_3、CeF_3相似,说明它们是固溶体。而Ca置换RE含量较多时,如Y_(0.71)Ca_(0.29)F_(3-y)、Gd_(0.85)Ca_(0.15)F_(3-主)的X射线衍射分析结果却与相应的YF_3和GdF_3完全不

电制冷Si-PIN X射线谱仪的研制

X射线谱仪以其多用途、无损、操作简单、快速、价格低廉和运行费用很低等优点，己经成为应用最为广泛的多元素分析仪器。采用液氮冷却的X射线谱仪在荧光分析技术领域得到广泛的应用和普遍认可。液氮制冷的一个主要缺点是必须有一个液氮存储罐作为完整谱仪的一部分。从而，在实际应用中受到液氮价格贵和液氮供应厂少的限制，大大地制约了该种谱仪的进一步推广使用。如果能采用另外的技术得到足够低的温度，在此温度下探测器具有极低的漏电流，也可使X射线谱仪有极低的噪声和相当好的能量分辨率；因此克服上述限制就成为一个有重要意义的课题方向。本文在国内首次实现采用半导体电制冷技术对平面离子注入（Si一PIN）探测器制冷，降低探测器漏电流至10~(-13)以下，配合低噪声脉冲光反馈前放，成功地使得整个x射线谱仪能量分辨率达到262eV（对~(55)Fe的Mn Kα K射线）。虽然电制冷X射线谱仪的分辨率没有采用液氮冷却的好，但是它的性能已足够在包括利用X射线能量分离进行荧光分析等多种应用所需。考虑到元素周期表中钾元素以上的毗邻两元素的Ka特征X射线的能量差在380eV以上；例如，K和Ca的峰线宽分别是243eV和245 eV，由此得到电制冷X射线谱仪己可完成对K, C a和更高Z的元素进行能散荧光分析工作。并且，液氮罐的取消可方便的设计在野外使用的便携式X射线荧光分析设备。 文中全面介绍了X射线谱仪的各个组成部分和其背景知识。并详细描述了探测器系统、电制冷系统和低噪声电子学系统，充分展示了研制X射线谱仪的关键所在。最后给出了电制冷X射线谱仪的测试结果和应用设计。

Self-immobilized metallocene catalysts bearing an allyl group for ethylene polymerization, X-ray crystal structure of [(CH2=CHCH2)CH3Si(C13H8)(2)]ZrCl2

A series of ansa-metallocene complexes with an allyl substituted silane bridge [(CH =CHCH2)CH3Si(C5H4)(2)]TiCl2 (1), [(CH2=CHCH2)CH3Si(C9H6)(2)]MCl2 [M = Ti (2), Zr (3), Hf (4)] and [(CH2=CHCH2)CH3Si(C13H8)(2)]ZrCl2 (6) have been synthesized and characterized. The molecular structure of 6 has been determined by X-ray crystallographic analysis. Complexes 1-4, 6 bearing allyl groups have been investigated as self-immobilized catalysts for ethylene polymerization in the presence of MMAO. The results showed that the self-immobilized catalysts 1-4, 6 kept high ethylene polymerization activities of ca. 10(6) g PE mol(-1) M h(-1) and high molecular weight (M-w approximate to 10(5)) of polyethylene.

Ce_(1-x)Ca_xO_(2-x)的溶胶-凝胶法的合成及其性质

用溶胶 -凝胶法合成了 Ce1-x Cax O2 -x(x=0～ 0 .3 5 )系列固体电解质 ,系统地研究了其晶体结构随Ca O含量的变化关系 .XRD测试表明 ,该体系于 1 60℃即形成萤石结构纯相 .高温 XRD表明 ,从室温至80 0℃ ,Ce1-x Cax O2 -x(x=0～ 0 .3 5 )未出现结构相变 .此法合成温度远低于传统的高温固相合成法和水热合成法的温度 .合成物的颗粒小 ,粒度均匀 .在 1 3 0 0℃即可烧结成高致密度样品 .XPS测试表明 ,掺杂 Ca O后吸附氧浓度明显增大 ,氧空位增多 ,电导率和氧离子迁移数增大 ,改善了 Ce O2 基固体电解质的性能 .

Calculation of chemical bond parameters in La1-xCaxCrO3 (0.0 <= x <= 0.3)

The chemical bond parameters, that is, bond covalency, bond susceptibility, and macroscopic linear susceptibility of La1-xCaxCrO3 (x = 0.0, 0.1, 0.2, 0.3) has been calculated using a semiempirical method. This method is the generalization of the dielectric description theory proposed by Phillips, Van Vechten, Levine, and Tanaka (PVLT). In the calculation of bond valence, two schemes were adopted. One is the bond valence sums (BVS) scheme, and the other is the equal-valence scheme. Both schemes suggest that for the title compounds bond covalency and bond susceptibility are mainly influenced by bond valence and are insensitive to the Ca doping level or structural change. Larger bond valences usually result in higher bond covalency and bond susceptibility. The macroscopic linear susceptibility increases (only slightly for BVS scheme) with the increasing Ca doping level. (C) 1999 John Wiley & Sons, Inc.

CaCl_2-KCl熔体结构的X射线衍射分析

用高温液态X射线衍射方法,测定了摩尔比为1∶2的CaCl_2-KCl熔体的径向分布函数。结果表明,熔体中Ca~(2+)-Cl~-、K~+-Cl~-和Cl~--Cl~-离子对间的最近邻距离分别为0.278,0.306和0.380nm.由于Ca~(2+)与Cl-间的强Coulomb作用,在熔融的摩尔比为1∶2的CaCl_2-KGl体系中,Cl~--Cl~-间的最近邻距离明显小于纯KCl熔体中Cl~--Cl~-间的最近邻距离。

SUPERCONDUCTIVITY IN BI1.5PB0.4SBXSR2CA2CU2OY SYSTEM (X=0-0.32)

The effect of doping with various amount of Sb (0.06-0.32) to (Bi,Pb):Sr:Ca:Cu = 1:1:1:1 system were studied with XRD and Tc measurements. The presence of Sb promotes the conversion of low Tc phase (2212 phase) to high Tc phase (2223 phase) and at around Sb = 0.18 the 2212 phase nearly completely disappears; but at the same time a new phase of unknown structure appears even with Sb = 0.06 showing that the incorporation of Sb into the Bi-based superconducting phase is of very low concentration. Tc measurements show that the optimum concentration of Sb-doping is around 0.10 and that unknown phase has an adverse effect to the superconducting properties; a composition disproportion at the surface of pellet was observed.

X-射线荧光光谱法分析面粉、大米中的微量元素

本方法是将消解后的面粉和大米样品溶液滴加于粘贴在聚酯薄膜上的薄纸片上,用薄纸片来控制样品面积及富集被测元素,用于X-射线荧光光谱分析。该方法只用被测元素的标准溶液计算回归方程的系数,无需大量的标样,针对不同的元素选择不同的扣除背景的方法和不同的回归方程,使结果更准确。通过测定样品中的K、Ca、Mn、Zn、Fe、Cu、As、Se等元素,并与美国NBS标样参考值比较,结果基本一致。

Sr_3Cu_5O_(8+x)和CaSrCu_5O_(5+x)的结构和电学性质

继Y-Ba-Cu-O之后,具有更高T_5的Bi-Sr-Ca-Cu-O(简称BSCCO)体系的发现引起了人们对高温超导研究的兴趣。研究表明,在BSCCO中存在110K和80K2个超导相。由于在制备BSCCO过程中存在复杂的Ca、Sr和Cu复合氧化物,要得到稳定的110K相相当困

Y_(1-x)Ca_xBa_2Cu_3O_(7-y)超导材料的研究

研究了Y_(1-x)Ca_xBa_2Cu_3O_(7-y)系超导材料,当x≤0.15时,钙离子部分置换了123相中钇离子而形成固溶体,导致正交相晶胞参数稍微增大。钙含量增加,三价铜的含量上升,T_c却下降。由于钙离子取代钇离子后主要影响邻近的Cu(2)-O层的性质,这说明Cu(2)-O层的性质对超导电性起了很重要的作用。