Magnetic Behavior of Some Rare-Earth Transition-Metal Perovskite Oxide Systems

Magnetic properties were investigated for the rare-earth 3d-transition metal oxides with the perovskite structure. Intriguing magnetic phenomena were reviewed for a few systems:magnetization peak effect in the titanates, magnetization reversal in the chromites and metallic ferromagnetism in the cobahites. The results suggest an important role of the rare-earth ions for the magnetic properties of such complex oxides.     

Studies on electrical properties and CO-sensing characteristics of La_（0.9） _（0.1）FeO_3

Semiconducting sensors offer an inexpensive and simple method for monitoring gases. Sensors based on the ABO3-type composite oxides materials have an advantage of high stability. The perovskite structures of these compounds are preserved, when an A-site deficiency of some perovskite structure compounds was formed. However, they exhibit particular physical properties. In this paper, La0.9 0.1FeO3 powder with an orthorhombic perovskite phase was prepared by sol-gel method. The electrical properties and CO-sensing characteristics of the La0.9 0.1FeO3 were also investigated. The results demonstrated that the La0.9 0.1FeO3 was a p-type semiconductor material. Compared with LaFeO3, the conductance of La0.9 0.1FeO3 was better than that of LaFeO3. The sensor based on La0.9 0.1FeO3 showed excellent CO gas-sensing characteristics.     

Electrical and CO-sensing properties of NdFe_(1–x)Co_xO_3 perovskite system

NdFe1–xCoxO3 (x=0.0–0.5) powders were prepared by a sol-gel citric method. X-ray diffraction was used to confirm the phase composition of the powders. All the samples are orthorhombic structure. The unit cell volume and grain size decreased with an increase of Co content x. The conduction type of the NdFe1–xCoxO3 perovskite oxides changed with the increasing Co content x. When x<0.3, the oxides showed p-type conduction behavior, and then changed to n-type when x>0.3. All the sensors presented higher respons...     

双钙钛矿光催化剂材料研究进展

钙钛矿材料具有化学结构稳定、种类繁多、可调性好等优点，目前广泛应用于光催化技术。然而，简单钙钛矿在光催化应用上存在光吸收效果差、带隙较大、耐湿性差等缺点。研究发现双钙钛矿相较简单钙钛矿具有更好的稳定性、更复杂的原子环境和更大的组成空间，可以容纳高价元素等，因此，双钙钛矿得到更加深入的研究。主要叙述了近年来双钙钛矿型光催化剂的研究进展，分别对有序双钙钛矿、无铅卤化物双钙钛矿、复杂双钙钛矿、氧缺陷双钙钛矿等光催化剂的研究进展进行了总结，并对双钙钛矿光催化反应机理进行了分析，认为双钙钛矿可以有效提高电子-空穴的分离效率，改善催化剂的晶体结构和光吸收性能，实现光催化性能的调控。最后对双钙钛矿光催化剂的发展和研究方向提出了展望。      

中温固体氧化物燃料电池电解质材料的研究进展

评述了中温固体氧化物燃料电池（中温SOFC）中固体电解质的研究进展，对ZrO2基、CeO2基、Bi2O3基和ABO3型的钙钛矿类4种电解质材料的最新进展和今后的发展趋势作了评述。对几种电解质材料的优缺点进行了分析，同时对高温电解质YSZ薄膜化技术也作了简要介绍，因此不难得出，寻求新的、优良的中温SOFC的电解质材料仍然是新世纪推动中温SOFC实用化的关键任务之一，而YSZ薄膜化技术的研究则是研究的另一个重点，且最有可能取得突破。     

铁酸镧薄膜的研究进展

铁酸镧(LaFeO3)是一种典型的具有钙钛矿(ABO3)结构的稀土复合金属氧化物,由于具有稳定的晶体结构、独特的电磁、催化和气敏性等特点,因此它在电学、磁学和传感器等领域都有着广泛的应用前景而成为国内外研究的热点.此外,LaFeO3还是少数的同时具有反铁磁性和铁电性的单相多铁材料之一,在信息存储、磁传感器和自旋电子器件等方面都有潜在的应用前景.本文综述了LaFeO3薄膜的结构及性能、制备工艺的研究进展,并展望了LaFeO3薄膜研究趋势.     

Status of Research on Application of High Purity Rare Earth Oxides in Solid Oxide Fuel Cells

The solid oxide fuel cell (SOFC) is a high-efficient and environmentally friendly power generation system.The rare earth oxide materials are used extensively in the manufacturing of SOFC components.In particular, the CeO2doped with Gd2O3 or Sm2O3, lanthanide perovskite oxides are indispensable and key materials for developing the intermediate temperature SOFC.The research and development status of application of high purity rare earth oxides in SOFC was overviewed.The rare earth oxide-based and -doped materials were discussed for the SOFC components.Concerning the rare earth oxides applicable to SOFC, several topics were also pointed out for further researching and developing.     

Catalytic combustion of diesel soot over K2NiF4-type oxides La2-xKxCuO4

Nanostructure K2NiF4 type oxides La2-xKxCuO4 complex oxides were prepared using the Sol-Gel method, characterized by X-Ray Diffraction （XRD）, Fourier Transform Infrared （FT-IR）, and Scanning Electron Microscopy （SEM）. The catalytic activity for soot combustion was evaluated by the Temperature-Programmed Reaction （TPO） technique. The results demonstrated that the substitution quality of K^＋ for La^3＋ at the A-site would increase the catalytic activities of La2-xKxCuO4 for soot combustion greatly; the substitution quality affected the structure and catalytic activity obviously. The La1.8K0.2CuO4 complex oxides with tetrahedral structures had the best catalytic activity for soot combustion, and the ignition temperature of soot combustion was lowered from 490 to 320 ℃.     

Preparation of double perovskite-type oxide LaSrFeCoO_6 for chemical looping steam methane reforming to produce syngas and hydrogen

Double-perovskite type oxide LaSrFeCoO_6 was used as oxygen carrier for chemical looping steam methane reforming(CL-SMR) due to its unique structure and reactivity. Solid-phase, amorphous alloy, sol-gel and micro-emulsion methods were used to prepare the LaSrFeCoO_6 samples, and the as-prepared samples were characterized by means of X-ray diffraction(XRD), hydrogen temperature-programmed reduction(H_2-TPR), X-ray photoelectron spectroscopy(XPS), Brunauer-Emmett-Teller(BET) surface area. Results showed that the samples made by the four different methods exhibited pure crystalline perovskite structure. The ordered double perovskite LaSrFeCoO_6 was regarded as a regular arrangement of alternating FeO_6 and CoO_6 corner-shared octahedra, with La and Sr cations occupying the voids in between the octahedral. Because the La~(3+) and Sr~(2+) ions in A-site did not take part in reaction, the TPR patterns showed the reductive properties of the B-site metals. The reduction peaks at low temperature revealed the reduction of adsorbed oxygen on surface and combined with the reduction of Co~(3+) to Co~(2+) and to Co~0, while the reduction of Fe~(3+) to Fe~(2+) and the partial reduction of Fe~(2+) to Fe~0 occurred at higher temperatures. From the point of view of the oxygen-donation ability, resistance to carbon formation, as well as hydrogen generation capacity, the sample made by micro-emulsion method exhibited the best reactivity. Its redox reactivity was very stable in ten successive cycles without deactivation. Compared to the single perovskite-type oxides LaFeO_3 and LaCoO_3, the double perovskite LaSrFeCoO_6 exhibited better syngas and hydrogen generation capacity.     

Phase Behavior of Rare Earth Manganites

Among complex oxides containing rare earth and manganese BaLn2Mn2O7(Ln=rare earth) with the layered perovskite type and Ln2(Mn,M)O7 with pyrochlore-related structure were studied since these compounds show many kinds of phases and unique phase transitions. In BaLn2Mn2O7 there appear many phases, depending on the synthetic conditions for each rare earth. The tetragonal phase of so-called Ruddlesden-Popper type is the fundamental structure and many kinds of deformed modification of this structure are obtained. For BaEuzMn207 at least five phases have been identified from the re-sults of X-ray diffraction analysis with the space group P42/mnm, Fmmm, Immm and A2/m in addition to the fundamental tetragonal 14/mmm phase. In the pyrochlore-related type compounds, LnzMn2-xMxO7(M=Ta,Nb,W etc),there also appear several phases with different crystal structures. With regard to every rare earth, Ln2MnTaO7 phase is stable only for excess Ta and can be obtained under high oxygen partial pressure process. This group has trigonal structure with zirkelite type (P3121 space group). On the other hand Ln2Mn2/3Nb4/307 phase has monoclinic (C2/c space group)and zireonolite type structure. All of these structural models have the fundamental structure based on HTB (hexagonal tungsten bronze) layers formed by the arrangement of oxygen octahedra.     

Ba_2CaMO_6(M=Mo,W)的制备及其光催化降解酸性红B的性能

以硝酸钡、氧化钙和钼酸铵(钨酸铵)为原料,用溶胶凝胶法和溶胶凝胶-低温自燃烧的方法合成了双钙钛矿复合氧化物Ba2CaMO6(M=Mo,W),用X射线衍射和扫描电镜对制得的样品进行表征,并测试样品在400W高压汞灯照射下光催化降解酸性红B的活性。分别考察溶胶凝胶法合成样品时柠檬酸加入量对样品性能的影响和溶胶凝胶-低温自燃烧法合成样品时硝酸加入量对样品性能的影响。结果显示,溶胶凝胶法制得了形状规则的Ba2CaMO6(M=Mo,W)颗粒,其中的Ba2CaWO6具有光催化活性,且增加配合剂柠檬酸的用量可以提高Ba2CaWO6的光催化活性;溶胶凝胶-低温自燃烧法制得形状不规则的Ba2CaMO6(M=Mo,W)颗粒,一定范围内增加硝酸用量可以改善Ba2CaWO6的活性。紫外光照射下,Ba2CaMoO6没有显示出光催化降解酸性红B的活性。     

Synthesis of La_xK_(1–x)CoO_3 nanorod and their catalytic performances for CO oxidation

A series of Lax K1–x CoO3 nanorod oxides with perovskite structure were synthesized by sol-gel method using polyvinyl alcohol(PVA) as additive.These perovskite-type complex oxide catalysts were characterized by the techniques of X-ray diffraction(XRD),infrared(IR),Brumauer-Emmett-Teller(BET) and scanning electron microscopy(SEM).And the results showed that nanorods of La1–x Kx CoO3 perovskite-type complex oxides were fabricated by sol-gel method when the mass concentration of PVA was 4% and the calcined temperature kept at 700 ℃ for 4 h.The catalytic results of CO oxidation showed that the Lax K1–x CoO3 catalysts had high activity.LaCoO3 nanorods exposed more {110} plane than LaCoO3 nanoparticles,which was beneficial to the catalytic oxidation of CO.LaCoO3 nanorods had the best catalytic performance for the oxidation of CO.At 200 oC,the CO conversion could reach 100%.     

Thermogravimetric Study on Oxygen Adsorption/Desorption Properties of Double Perovskite Structure Oxides REBaCo2O（5＋δ）（RE= Pr,Gd,Y）

The oxygen adsorption/desorption properties of double perovskite structure oxides PrBaCo2O5＋δ,GdBaCo2O5＋δ,and YBaCo2O5＋δ were investigated by the thermogravimetry（TG）method in the temperature range of 400~900 ℃.The calculated oxygen adsorption/desorption surface reaction rate constants ka and kd of these double perovskite structure oxides were larger than the commonly used cubic perovskite oxides,such as Ba0.95Ca0.05Co0.8Fe0.2O3-δ and Ba0.5Sr0.5Co0.8Fe0.2O3-δ,whereas,the oxygen permeation flux was comparable to that of the latter,which was attributed to the smaller difference of oxygen vacancy in oxygen and nitrogen atmosphere（Δδ/Vmol）in these double perovskite structure oxides.The large oxygen adsorption/desorption rate constants of GdBaCo2O5＋δ and PrBaCo2O5＋δ made them nice catalyst coating materials,on other membrane surfaces,to improve the oxygen permeability.     

Effect of template on catalytic performance of La_(0.7)Ce_(0.3)Ni_(0.7)Fe_(0.3)O_3 for ethanol steam reforming reaction

Perovskite-type oxides La_(0.7)Ce_(0.3)Ni_(0.7)Fe_(0.3)O_3(LCNF) were synthesized by polystyrene colloidal crystal templating(LCNF-CCT) and polystyrene polymer templating(LCNF-PS) through co-precipitation. The structure and physicochemical properties of the obtained oxides were investigated by scanning electron microscopy, X-ray diffraction, N_2 adsorption-desorption, Fourier transform infrared spectrometry, H_2 temperature-programmed reduction and H_2 temperature-programmed desorption, as well as X-ray photoelectron spectroscopy. The results show that the as-synthesized LCNF-CCT perovskite possesses large specific surface area and regular pore size distribution. In addition, the formation of additional oxygen vacancies on the surface favors the migration of lattice oxygen from the bulk phase to the surface and production of more metallic sites, thus improving the activity and resistance to carbon deposition of catalysts in ethanol steam reforming reaction.     

钙处理对成品无取向硅钢夹杂物特性的影响

通过取样检测结合热力学计算,分析了钙处理对成品无取向硅钢中夹杂物特征及硫化物夹杂的析出机制的影响。结果表明,钢中尺寸大于3μm的有害夹杂物主要是AlN、MgO-SiO2、CaO-Al2O3-SiO2类复合夹杂物及其与MgS、MnS、CaS的复合析出物。钙处理钢中没有检测到单独的Al2O3、SiO2及铝酸钙类夹杂物。钙处理钢中形成的液态3CaO·Al2O3、MgO·SiO2和Al2O3夹杂物被精炼渣吸收,改性去除了钢中大尺寸Al2O3夹杂物。钙处理钢中尺寸大于3μm的氧化物夹杂主要是含CaO和(或)CaS的Al2O3-SiO2类夹杂。硫化物在MgO-SiO2类氧化物表面的析出有利于其形貌趋于规则。钢中不同形貌的AlN夹杂物呈多尺度分布,钙处理对大尺寸AlN的析出特性影响不大。氧硫化物及其与AlN复合析出并定向长大的过程,与其晶体结构有关。氧化物夹杂的硫容量决定了其与硫复合的难易程度。钙处理钢中CaS在氧化物表面呈局部包裹析出和局部吸附析出。     

双参数模型估算复合氧化物的标准生成焓

 提出了估算二元复合氧化物标准生成焓的双参数模型,包括线性双参数模型和对数双参数模型。用此模型可估算由CaO、SiO2、TiO2等32个简单氧化物之间形成的二元复合氧化物的标准生成焓。在估算已知的207个二元复合氧化物标准生成焓时,平均误差为1081 kJ/mol,标准差为1418 kJ/mol。用提出的线性双参数模型还可估算三元复合氧化物的标准生成焓,在估算已知的22个三元复合氧化物标准生成焓时,平均误差为180 kJ/mol,标准差为228 kJ/mol,平均相对误差为053%,最大相对误差为157%。     

Solid state reaction synthesis and total electrical conductivity of La_(0.7)Sr_(0.3)Cr_yMn_zCo_(1-y-z)O_(3-δ)

The La0.7Sr0.3CryMnzCo(1-y-z)O3-δ samples were prepared by solid state reaction.The phases,microstructure and properties of the samples were investigated by XRD,SEM,DC four-probe method and iodometry method.The single orthorhombic phase La0.7Sr0.3CryMnzCo(1-y-z)O3-δ perovskite oxides were obtained when sintered at l350 °C for 10 h.The oxygen nonstoichiometry of the materials varied inversely with the total electronic conductivity.The sample with composition of La0.7Sr0.3Cr0.5Mn0.35 Co0.15O3-δ had the maximal total electronic conductivity and the lowest oxygen nonstoichiometry which were 22.4 S/cm and 0.040 at 850 °C,respectively.The low total electronic conductivity is related to the low relatively density of the samples directly.The activation energy of conduction changed at 550 °C,and the activation energy of conduction at high temperature(T550 °C) was higher than that at low temperature range(T550 °C).     

Mechanical Activation-Assisted Synthesis of Nd-BaPbO3

ThesimpleperovskiteBaPbO3hasbeenreportedtohavehighelectricalconductivityandorthorhombicsymmetry[1～ 3] .Matherssetal .[4 ] reportedthehighconductivityofthismaterialoriginatesfromtheforma tionofabroadbandduetomixingoflead 6sandoxy gen 2pstates .Substitutionand/ornonstoichiometryinBaPbO3induceinterestingelectricalproperties .Forexample ,Sleightetal .[3] foundthesuperconductivityofBaPb1-xBixO3intherangeofx =0 .0 5～ 0 .3in1975 .IncreasingattentionhasbeenfocusedonBaP bO3asacomponentofthemate…     

Study of Physicochemical Properties and Active Oxygen in Structures of Layered Mixed La_4BaCu_5-_xM_xO_(13 λ)(M=Mn,Co)

ＴｈｅｒｅｉｓｐｒｏｆｕｓｅｒｅｓｏｕｒｃｅｏｆｒａｒｅｅａｒｔｈｅｌｅｍｅｎｔｉｎＣｈｉｎａ,ｓｏｉｔｉｓｖｅｒｙｉｍｐｏｒｔａｎｔｔｏｓｔｕｄｙｔｈｅａｐｐｌｉｃａｔｉｏｎｏｆｔｈｅｒａｒｅｅａｒｔｈｃｏｍｐｏｕｎｄｓ［１］．Ｔｈｅｐｅｒｏｖｓ...     

Application of phase diagrams to predict phases formed during deoxidation of steel

Phase diagrams for simple ternary systems such as Fe-Al-O, Fe-Si-O and more complex systems Fe-Mn-Al-O, Fe-Mn-Si-O have been used to rationalize some of the observations made during deoxidation. The formation of less stable oxides such as liquid aluminates and spinel is shown to be a consequence of the reaction path followed by the metal-inclusion system. The significance of univariant conditions in which three phases are in equilibrium is brought out. During cooling and solidification inclusions may change from a solid oxide to a liquid oxide phase and vice versa. This causes a change in solidification from eutectic type to a monotectic type. The existence of a saddle point at which either a eutectic or monotectic solidification begins is established and its significance in semi-killed steel is brought out.