Sr2FeMoO6的微波合成及对酸性黑10B的降解性能研究

以MnO2为微波吸收剂,SrCO3、Fe2O3、MoO3为原料,采用微波烧结法合成了双钙钛矿型复合氧化物Sr2FeMoO6。通过X射线衍射仪对样品的物相结构进行了分析表征,采用标准四引线法测量了样品在零场下的电输运性质,采用紫外可见分光光度计测试了样品降解酸性黑10B的活性。结果表明:Sr2FeMoO6为四方晶系结构,空间群为I4/mmm,晶胞参数为:a=0.558 7nm,c=0.789 4nm,晶胞体积V=0.246 4nm3;在80～300K温度范围内,呈现典型的半导体性质。样品Sr2FeMoO6对酸性黑10B有很高的降解活性,在适宜条件下,脱色率可达98%左右。同时对脱色机理进行了探讨。     

Bulrush-like double perovskite: synthesis, tunneling magnetoresistance, and magnetocaloric effects

The recent observation of room temperature tunneling magnetoresistance (TMR) in half-metallic A2FeMoO6 (A = Ca, Sr, Ba) double perovskites, and their importance to the emerging field of spintronics has led to considerable effort being dedicated to detailed investigations of the physical and chemical properties of these materials. This article will present an review of our recent investigations covering the synthesis, structures, magnetic and transport properties of "bulrush-like" A2FeMoO6 (A = Sr, Ba). Utilizing the high shape anisotropy as well as the reactivity of A2FeMoO6 to water and a sonochemical technique, we managed to manipulate the properties of grain boundary barriers, and thus put forward a new approach for the enhancement of room temperature TMR. The magnetocaloric effects of A2FeMoO6 double perovskites will also be discussed.     

Interrelation among superstructural ordering,oxygen nonstoichiometry and lattice strain of double perovskite Sr2FeMoO6−δ materials

Journal of Materials Science - Double perovskite ceramics Sr2FeMoO6?δ having different amount of antisite disordering and oxygen content are prepared by the solid-phase reaction method...     

溶胶-凝胶法制备超细Sr_2FeMoO_6及磁性能研究

以活性炭为还原剂,采用溶胶-凝胶法制备双钙钛矿结构巨磁电阻材料Sr_2FeMoO_6.经XRD物相分析证明,产品为四方晶系Sr_2FeMoO_6,空间群为I4/mmm,晶胞参数:a=0.558nm,c=0.7882nm.SEM形貌分析表明,粉体颗粒分散性较好,粒子基本为球形,尺寸在100nm以下.磁性能测试结果表明,样品的居里温度高于室温,1T磁场下室温饱和磁化强度为13.59A·m~2·kg~(-1).     

稀土掺杂双钙钛矿结构红色荧光粉的制备及其发光性能

采用高温固相反应法制备了Sr_(2-x)BaxMgMoO_6∶Eu~(3+)(x=0~1)双钙钛矿结构红色荧光粉。探讨了预处理及煅烧制度、Ba取代量对Sr_(2-x)BaxMgMoO_6∶Eu~(3+)荧光粉的相结构和发光性能的影响。Sr_2Mg_(0.94)Eu_(0.06)MoO_6荧光粉最佳制备工艺为:在700℃下预处理1h再升温至1050℃预处理1h并随炉降温后研细,再在1300℃煅烧4h,所得样品主相为双钙钛矿结构的Sr2MgMoO6四方相。其最强发光峰位于617nm附近,对应于Eu3+的5D0→7F2电偶极跃迁。随着Ba2+对Sr2+的取代量的增加晶体对称性提高,晶体结构由四方相变为立方相,样品的激发峰强度显著提高。由于晶体对称性的提高,抑制了荧光粉在617nm处5D0→7F2红光发射,其发光由电偶极跃迁占主导转变为磁偶极跃迁占主导。     

Superconductivity in (Bi,Pb)2Ca2Sr2Cu3−xVxOy

The superconducting properties of V-doped (Bi,Pb)2Sr2Ca2Cu3Oy (2223) samples have been investigated by means of X-ray diffraction and electrical resistivity measurements. The volume fraction of the 2223 phase decreases with a decrease in the c lattice parameter. The onset of superconductivity in the samples remains almost constant while the temperature at which the resistivity becomes zero decreases with increasing dopant content. The electrical resistivity data suggest that the substitution of copper by vanadium suppresses the superconductivity in (Bi,Pb)2Sr2Ca2Cu3–xVxOy by destroying the phase coherence and by pair-breaking effects. The suppression of superconductivity in the system could also be due to a decrease in the carrier concentration.     

Structure and electrical properties of strontium barium niobate ceramics

SBN, x=0.25, 0.35, 0.50, 0.60 and 0.75 series of ceramics prepared by traditional sintering method have been studied systematically. The impact of composition and sintering temperature on structures, microstructures, and electrical properties of SBN ceramics was characterized of X-ray diffraction, scanning electron microscopy, and electrical measurements. It is found that the composition and temperature play an important role on the fabrication of single phase tetragonal TTB SBN ceramics. At x=0.5, TTB SBN ceramics can be obtained at 1200°C. For x<0.5, it consists of a mixture of TTB structure SBN and orthorhombic phase BaNb₂O₆ even at 1300°C; TTB structure SBN and orthorhombic phase SrNb₂O₆ for x>0.5. The complete TTB phase is produced at 1350°C. With Sr content increasing, the electrical performances show a regular change, strongly conforming to the reducing of the Curie temperature. SBN with the Sr composition of x=0.60-0.75 is a promising candidate for electro-optics device applications.     

钒酸锶(Sr2V2O7)氧敏电阻特性的研究

通过钒酸锶电阻特性的研究，评估其作为电阻型氧敏传感器的可能性．实验中测量了不同温度下钒酸锶陶瓷片的体电阻和不同温度、不同氧压下的表面电阻，对实验数据进行数学处理后，得到钒酸锶材料的一些性质：相变对其电阻特性的影响很小；体电阻和面电阻的激活能分别为1．31eV和191eV；表面电阻的氧敏因子m＝6；温度系数相对较大．所以钒酸锶要作为尾气传感器材料，需考虑进行表面改性．     

Second phase development in Sr-doped TiO2

In the Ti-rich region of the SrO-TiO₂ system, a temperature-composition range is found to exhibit limited solubility of strontium, the maximum limit being 0.5 mol % Sr. It is also found that a two-phase region exists between this solubility limit and SrTiO₃, in agreement with existing phase diagrams. When the strontium concentration is small (? 0.5 mol %), strontium segregates to the grain boundaries to form a second phase of SrTiO₃ below the solubility limit. Above 1200? C, this second phase is continuous; shape instability causes it to break up into discrete particles below 1200? C. At higher strontium concentration (about 2 mol % Sr), nucleation of SrTiO₃ crystallites occurs both inside the TiO₂ grains and at the grain boundaries. The morphology of these crystallites after long time annealing suggests that the {110} plane has the fastest growth rate. The appropriate range of composition and heat treatment to form a continuous SrTiO₃ grain boundary layer is discussed in relation to the optimum heat treatment to develop the best nonlinear electrical properties of varistor devices.     

钴掺杂Sr_4Fe_6O_(13)混合导体氧化物结构及透氧测定

用湿化学法合成了Ｓｒ４ＣｏｘＦｅ６－ｘＯ１３±δ系列混合导体氧化物,对其相结构与透氧性能进行了研究．钴离子的引入导致材料中钙钛矿型杂相的出现,Ｘ＝２．０时材料中还产生了ＣｏＯ杂相,ｘ＝２．６时材料呈现钙钛矿型结构．Ｓｒ４Ｆｅ４Ｃｏ２Ｏ１３±δ的相结构还与焙烧温度及环境气氛中的氧浓度密切相关．随着氧浓度的降低,材料从纯相Ｓｒ４Ｆｅ６Ｏ１３结构（纯氧气气氛下）转变为Ｓｒ４Ｆｅ６Ｏ１３结构、钙钛矿型结构和ＣｏＯ共存（空气气氛下）,直至转变为针镍矿结构、 Ｓｒ４Ｆｅ６Ｏ１３结构和 ＣｏＯ共存． Ｓｒ４Ｆｅ６Ｃｏ１３±δ导体膜在ａｉｒ／Ｈｅ氧浓差梯度下的透氧量为 １．５×１０８ｍｏｌ／ｃｍ２·ｓ（８５０℃）,在６５０～８５０℃范围内透氧活化能为７０ｋＪ／ｍｏｌ．     

Rhenium oxides having an ordered or related perovskite-type structure

Further structural and magnetic observations on compounds of the type A₂BReO₆ (where A = Ca, Sr, Ba; B = Ca, Sr) having the perovskite-related structure were carried out. The thermal decomposition of Ca₅Re₂O₁₂ in vacuo yielded single crystals of a perovskite related phase having the composition Ca₃ReO_5.5. The crystallo-graphic properties for all the derivatives were obtained from powder diffraction studies. Magnetic and electrical results on these phases are reported.     

Sintering effect on Bi(Pb)–Sr–Ca–Cu–O high-Tc superconductors

D. c. electrical resistivity, a.c. magnetic susceptibility and X-ray diffraction techniques have been used to investigate the superconductive and structural properties in the systems Bi1.6Pb0.4Sr2Ca2Cu4.5OY and Bi1.6Pb0.2Sr2Ca2Cu4Oy. It is observed that the preparation method and heating methodology affect the properties of materials. Step sintering is of greater value for magnetic properties of the samples whereas prolonged sintering makes the systems more metallic and a smooth variation in resistivity with temperature is observed. The superconducting phase identified by X-ray diffraction analysis is mainly the high-Tc phase in all the samples. Resistivity and susceptibility measurements also indicate primarily the high-Tc phase. © 1998 Chapman & Hall     

Sr掺杂对WO3陶瓷电学性质及微观结构的影响

利用传统的陶瓷制备工艺制备了Sr掺杂的WO3陶瓷样品,测量了样品的显微结构和电学性质.结果表明,对于Sr掺杂来说,浓度为2 mol%是一个临界点,在这一点处电学性质和微观结构都将发生显著的变化.掺杂浓度为0.2 mol%的样品表现出较高的非线性系数8.7.实验中发现部分样品表现出电学的不稳定性,我们认为这种不稳定性与相共存以及由此导致的极化有关.     

多元掺杂LaCoO_3基混合导体的制备与性能研究

为开发新型高性能中温固体氧化物燃料电池阴极材料,采用改进的固相法制备了Sr2+、Ca2+与Fe3+多元掺杂LaCoO3基稀土复合氧化物La0.8Sr0.1Ca0.1Co0.7Fe0.3O2.9(LSCCF81173)和La0.7Sr0.2Ca0.1Co0.8Fe0.2O2.85(LSCCF72182).利用EDS、XRD、TG-DTA、SEM及热膨胀法等技术,对制备样品的化学成分、物相结构、形成过程、显微组织及热膨胀系数等进行分析,并采用直流四端子法测量样品在25～850℃的混合电导率.XRD和SEM分析表明,经1200℃烧结,LSCCF81173和LSCCF72182样品均具有单一的菱方钙钛矿相和孔隙尺寸与分布较均匀的多孔结构;EDS结果证实,制备的样品中基本不含其他杂质元素;在25～500℃较低温度区间,混合电导率与温度的关系近似为直线,说明较低温阶段样品的导电行为符合小极化子导电机制,且具有较低的导电活化能(Ea=0.07584eV和0.07798eV);Ca2+、Fe3+的共同掺杂有利于降低其热膨胀系数,改善与电解质的热匹配性,并对其原因进行了初步分析.     

Superconducting properties of 1212 phase in (Tl, M) Sr2(Ca1-xCrx)Cu2O7 (M=Zr and Ce)

Samples with nominal starting compositions (Tl0.8M0.2)Sr2(Ca1-xCrx)Cu2O7 (1212) where M=Ce and Zr have been prepared and investigated by the d.c. electrical resistance method and powder X-ray diffraction analyses. Most of the samples showed the 1212 as the major phase and 1201 as the minor phase. Both series of samples showed the highest superconducting onset temperature (Tc) at x=0.2. Ce was found to be more favourable for the formation of the 1212 phase compared to Zr. The valence state of Zr, estimated by employing previous results of optimum average Cu valence for superconductivity in the 1212 superconductors, is 4+. The importance of ionic radius of the substituted elements and the effect of starting composition on Tc and phase formation are discussed. © 1998 Chapman & Hall     

Formation of the fluorite phase and other related phases in the system Y2O3–Ta2O5–MO (M−Mg, Ca, Sr or Ba)

The formation of the fluorite phase Y0.8Ta0.2O1.7 and other related phases in the system Y2O3–Ta2O5–MO (M=Mg, Ca, Sr or Ba) has been studied. The single fluorite phase formed when up to 12 mol% MgO was added to the fluorite phase; however, MgO appeared as the second phase as well as the main fluorite phase when more than 16 mol% MgO was added. When more than 8 mol% CaO was added to Y0.8Ta0.2O1.7, Ca2YTaO6 and Y2O3 were produced as the second phases as well as the main fluorite phase. Ba2YTaO6 and Sr2YTaO6 of the perovskite-type ordered structure and Y2O3 were produced as well as the main fluorite phase when only 4 mol% BaO or SrO were added to Y0.8Ta0.2O17. The region of the fluorite single phase was found in the system Y2O3–Ta2O5–CaO. The formation of the fluorite phase is assumed to be related to the cation radius of the doped alkaline-earth oxide. © 1998 Chapman & Hall     

铅对(Pbx,Sr1-x)0.85Bi0.1TiO3薄膜结构与介电可调性影响的研究

用溶胶-凝胶法制备了（Pbx，Sr1-x）0．85Bi0．1TiO3薄膜，对其晶相结构、微观形貌和介电可调性进行了研究．结果表明，该薄膜以钙钛矿形式存在．快速热处理过程可分解得到高活性离子，直接形成比相应温度平衡状态析晶时更多的晶相量．这种晶相在一定条件下有分解和再结晶的趋势．随着Pb^2＋离子增加和Sr^2＋离子减少，钙钛矿相的四方相与立方相间的转变温度升高．薄膜处在铁电相和顺电相转变点附近时，可以获得较大的可调性．     

Investigation of Instability of Lattice of Bi_2Sr_2CaCu_2O_x

Bi2Sr2CaCu2Ox superconductor was studied by differential scanning calorimetry (DSC) and thermogravimetry (TG) in different atmospheres. It is discovered that there is a thermal anomaly in the DSC curve, associated with a weight loss in the TG curve before the melting of the sample. Careful thermal analysis and high temperature X-ray diffraction reveal that the thermal anomaly and the weight loss show an instability of the crystalline Iattice. By annealing the sample in oxygen and argon, respectively and then by TC measurement and thermal analysis, the coincidence of transition temperature with the instability is found. The coincidence is further confirmed by Y-doped 2212 phase.     

Sr0.4Ba0.6Nb2O6物相形成过程的XRD分析

采用X射线衍射技术（Guinier-Hagg相机）分析了Sr0.4Ba0.6Nb2O6（SBN40）原始混合粉料经不同温度煅烧后的相组成，并利用PIRUM程序对不同反应温度下形成铌酸锶钡相的晶胞尺寸进行了计算。结果表明：在Sr0.4Ba0.6Nb2O6的形成过程中将出现中间相Na5Nb4O15、Sr5Nb4O15、SrNb2O6与BaNb2O6，而SrNb2O6与BaNb2O6最终反应生成铌酸锶钡。反应生成的铌酸锶钡的晶胞参数随反应温度的升高而变小。依据这些实验结果，文中提出了Sr0.4Ba0.6Nb2O6相的形成机制。     

Particle morphology, electrical conductivity, crystal and electronic structures of hydrothermally synthesized (Ce,Sr)PO4

We focused on Sr-substituted CePO₄—i. e., (Ce,Sr)PO₄—with the monazite structure and synthesized the orthophosphates hydrothermally. As for the obtained products, we investigated the particle morphologies by SEM and electrical conduction properties by conductivity measurements. In order to estimate the crystal and electronic structures, neutron and synchrotron X-ray diffraction measurements were also carried out. As a result, it was found that (Ce,Sr)PO₄ with a single phase of the monazite structure was successfully prepared by the hydrothermal method and the substitution amount of Sr was almost equal to the nominal one. It was also demonstrated that a powder morphology of the (Ce,Sr)PO₄ depended on the synthetic conditions; i.e, concentrations of cation sources and pH of aqueous solution in the hydrothermal process. The Sr-substituted sample showed much higher conductivities than the unsubstituted one, in the same way as the (Ce,Sr)PO₄ synthesized by other methods reported previously.