Indentation strength method to determine the fracture toughness of La0.58Sr0.4Co0.2Fe0.8O3-δ and Ba0.5Sr0.5Co0.8Fe0.2O3-δ

The temperature-dependent fracture toughness of brittle ceramics can be conveniently assessed from bending tests of specimens with defined cracks introduced by indentation. However, the validity of this indentation strength in bending method (ISM) depends critically on the correct consideration of the residual stress induced by the indentation process. The ISM has been applied to La_0.58Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) and, for comparison, on Ba_0.5Sr_0.5Co_0.2Fe_0.8O_3-δ (BSCF) perovskite. LSCF with rhombohedral phase exhibits ferro-elastic behavior at ambient temperature, whereas BSCF deforms linear-elastically. Pre-indented specimens of both perovskites were fractured at room temperature in biaxial bending, some of them after an additional annealing step. The fracture toughness values of BSCF match reasonably well when determined with equations which consider the presence or absence of residual indentation stress. Interestingly, annealing has little influence on the apparent toughness results obtained for rhombohedral LSCF, which appears to be related with stress relaxation by ferro-elastic deformation.     

La0.6Sr0.4FeO3中反常超声特性研究

系统研究了La0.6Sr0.4FeO3单相多晶样品在低温下的电荷输运性质和超声特性.超声测量结果表明,La0.6Sr0.4FeO3在213K附近出现了明显的声速软化,其相对变化超过5%,同时超声衰减出现一个巨大的峰值,而电阻在这个温区内却没有明显的异常发生.分析指出这是由于电-声子相互作用导致的局部电荷发生有序态转变的结果,该电-声子耦合主要起源于Fe4+的Jahn-Teller效应.     

La0.6Sr0.4Co0.2Fe0.8O3-δ基固体氧化物电解池复合阳极的制备及性能

采用丝网印刷工艺制备了带有SDC阻挡层的固体氧化物电解池La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF)基复合阳极,利用动电位扫描及电化学阻抗谱分析考察了该材料在800℃时的电化学性能,电化学阻抗谱的研究表明,O2-在电极发生氧化反应生成O2的反应速率由电极/阻挡层界面的电荷转移、阻挡层/电解质界面的电荷转移以及氧气的解离吸附或在电极表面的扩散等三个电极过程控制.扫描电镜分析表明,经过长时间的电化学测试及升降温,阻挡层与电解质及复合电极部分均结合紧密,无缺陷.通过与传统的LSM-YSZ复合阳极的极化性能的对比,显示出LSCF材料在SOEC阳极领域良好的应用前景.     

Structural, Dielectric and Complex Impedance Spectroscopy Studies of Lead Free Ca0.5 ＋xNd0.5-x（Ti0.5 Fe0.5）O3

Structural and various electrical properties of polycrystalline Ca_0.05+xNd_0.5-x(Ti_0.5Fe_0.5)O₃,prepared by standard solid state reaction technique,were studied.Formation of single phase orthorhombic structure of the compositions was confirmed by X-ray diffraction study.The composition dependence of lattice parameters, density and microstructural study show that they vary significantly with Ca content.The dielectric measurements were carried out at room temperature as function of frequency and composition.The experimental results reveal that the dielectric constant（ε’） increases with increasing Ca content.Similar behavior is observed for the dielectric loss（tanδ） and ac conductivity(σ_ac).In complex impedance analysis it is observed that the real part（Z’） vs imaginary part（Z"） graph exhibits a tendency of formation of a single semicircular arc for each composition of samples.Different parameters were determined by fitting the experimental data in Cole—Cole empirical formula.A dominance of grain boundary resistance(R_gb) is observed.The R_gb decreases with increasing Ca content.The highε’ observed in present samples are suitable for fabrication of devices.     

Symmetry breaking and electrical conductivity of La0.7Sr0.3Cr0.4Mn0.6O3−δ perovskite as SOFC anode material

This work is focused on nanocrystalline solid oxide fuel cell synthesis and characterization (SOFC) anodes of La_0.7Sr_0.3Cr_0.4Mn_0.6O_3−δ (perovskite-type) with Nickel. Perovskite-type oxide chemical reactivity, nucleation kinetics and phase composition related with La_0.7Sr_0.3Cr_0.4Mn_0.6O_3−δ–NiO to La_0.7Sr_0.3Cr_0.4Mn_0.6O_3−δ–Ni transformation have been analyzed. SOFC anode powders were obtained by sol–gel synthesis, using polyvinyl alcohol as an organic precursor to get a porous cermet electrode after sintering at 1365 °C and oxide reduction by hydrogen at 800 °C/1050 °C for 8 h in a horizontal tubular reactor furnace under 10% H₂/N₂ atmosphere. Composite powders were compressed into 10-mm diameter discs with 25–75 wt% Ni.     

Gd0.2Ce0.8O2包覆LaNi0.6Fe0.4O3-δ阴极材料抗铬污染性能

应用丝网印刷和共烧结制备LaNi_0.6Fe_0.4O_3-δ (LNF)/Sc_0.1Zr_0.9O_1.95(ScSZ)/LaNi_0.6Fe_0.4O_3-δ 对称电池.以硝酸铈和硝酸钆为原料、柠檬酸为燃料,采用燃烧法制备质量分数为21.3%的Gd_0.2Ce_0.8O₂(GDC)包覆的LNF阴极.电化学阻抗谱(EIS)表明:在750 ℃工作温度下,当无Cr基合金接触时,质量分数21.3%的GDC包覆的LNF经过1 200 h的搁置,其极化电阻由0.13 Ω·cm²增加至0.40 Ω·cm²,而纯LNF经过500 h的搁置,极化电阻由0.70 Ω·cm²增加至2.36 Ω·cm²,GDC的包覆加速了气体/阴极/电解质三相界面反应区的扩散过程,降低了阴极极化电阻;当有Cr基合金接触时,相对于质量分数为21.3%的GDC包覆的LNF阴极,LNF/ScSZ界面处沉积出大量Cr₂O₃,减缓了活性粒子在三相界面处的扩散,故其极化电阻远大于相同条件下质量分数为21.3%的GDC包覆的LNF阴极的极化电阻,质量分数为21.3%的GDC包覆的LNF阴极具有较佳的抗铬污染性能.     

Significant improvement of the oxygen permeation flux of tubular Ba0.5Sr0.5Co0.8Fe0.2O3 − δ membranes covered by a thin La0.6Sr0.4Ti0.3Fe0.7O3 − δ layer

We present a new method to improve the oxygen flux properties and stability of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3 − δ tube membrane using a thin layer of La_0.6Sr_0.4Ti_0.3Fe_0.7O_3 − δ as protective coatings. The first relevant result is that the La_0.6Sr_0.4Ti_0.3Fe_0.7O_3 − δ protective layer had an extraordinary positive effect on improving the oxygen permeation flux of the tubular Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3 − δ membranes. La_0.6Sr_0.4Ti_0.3Fe_0.7O_3 − δ-coated Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3 − δ tubular membrane showed the highest oxygen permeability with the flux reaching ~ 3 ml cm⁻² min⁻¹ (oxygen purity > 99%) at 950 °C in static atmospheric pressure through a 1.0 mm thick membrane.     

The effect of A-site deficiency on the performance of La1−sFe0.4Ni0.6O3−δ cathodes

The effect of lowering the A-site stoichiometry of La-Fe-Ni based perovskite solid oxide fuel cell cathodes was investigated with electrochemical impedance spectroscopy on cone-shaped electrodes using a Ce_0.9Gd_0.1O_1.95 electrolyte. It was shown that a lowering of the A-site stoichiometry lowers the amount of Ni in the perovskite phase, as powder XRD revealed that NiO was expelled from the perovskite lattice when the A-site stoichiometry was decreased. NiO inhibit the reduction of oxygen as the activity of a nominally A-site deficient La_1−sFe_0.4Ni_0.6O_3−δ perovskite was worse than the activity of the corresponding LaFe_0.4+sNi_0.6−sO_3−δ perovskite without NiO. NiO is therefore poison for the reduction of oxygen at the cathode in a solid oxide fuel cell.     

硬脂酸凝胶法制备纯相LaNi0.6Fe0.4O3粉体的研究

以硬脂酸、氧化镧、硝酸镍和硝酸铁为原料采用硬脂酸凝胶法合成了纯相LaNi0.6Fe0.4O3粉体为避免制备过程中产生杂相,实验采用了直接煅烧法即先将炉内温度升至煅烧温度保持恒温,然后将凝胶置于炉内焙烧。在650℃下成功合成了LaNi0.6Fe0.4O3粉体。用差示扫描量热法(DSC)和热重分析(TG)对其热处理过程进行分析,并用X射线衍射分析(XRD)和扫描电镜(SEM)对其结构和形貌进行表征。结果表明,合成的LaNi0.6Fe0.4O3粉体纯度高、分散性好,粒径<1μm,且工艺过程简单,具有较好应用前景。     

Electrochemical performance of La2NiO4+δ-La0.6Sr0.4Co0.2Fe0.8O3−δ composite cathodes for intermediate temperature solid oxide fuel cells

The composite cathodes La₂NiO_4+δ-La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ were prepared for intermediate temperature solid oxide fuel cells. La₂NiO_4+δ and La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ powders were synthesized successfully by glycine-nitrate process. The effect of composition on the electrochemical performance of the composite electrodes was studied by AC impedance spectroscopy and the optimal calcination temperature was determined when the electrode showed the minimum area specific resistance. The addition of La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ to La₂NiO_4+δ electrode decreased the area specific resistance remarkably. The composite electrode with 30 wt% La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ calcined at 1150 °C exhibited the lowest area specific resistance of 0.125 Ω cm², about 60% of the area specific resistance of La₂NiO_4+δ electrode at 700 °C in air. The composite electrode with 30 wt% La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ can be a promising cathode material through the evaluation of electrical conductivity and thermal expansion behavior.     

La0.8Sr0.2CoxFe1-xO3型氧扩散障层材料的制备及结构性能研究

采用共沉淀-凝胶方法制备La0.8Sr0.2CoxFe1-xO3(x=1.0、0、0.3)氧扩散障碍层材料的前驱体,分别用X射线衍射分析、透射电镜、扫描电镜和交流阻抗谱仪对三种不同粉体及其陶瓷结构和性能进行研究.结果表明:在870℃下焙烧制备的La0.8Sr0.2CoxFe1-xO3(x=1.0、0、0.3)粉末具有钙钛矿相结构,无硬团聚,颗粒大小在20～60 nm.此粉末经冷等静压250MPa成型后,在1120℃下烧结6h,La0.8Sr0.2CoO3和La0.8Sr0.2FeO3混合导体的电导率在10—1S/cm数量级,而La0.8Sr0.2Co0.3Fe0.7O3导电率最高达100 S/cm数量级.三种陶瓷都是电子电导远大于离子电导的混合导体,电导率最高值在200～300℃范围,偏向低温.     

Co替代对纳米晶Ni0.4CoxZn0.6-xFe2O4结构和电磁性能的影响（英文）

采用聚丙烯酰胺凝胶法制备了尖晶石型纳米晶Ni0.4CoxZn0.6-xFe2O4(x=0、0.2、0.4),同时考察了铁氧体的电磁性能.由X射线衍射(XRD)可知,随着x的增大,Ni0.4CoxZn0.6-xFe2O4的晶格常数从0.838 4 nm减小到0.835 7 nm.透射电镜(TEM)结果表明,Ni0.4Zn0.6Fe2O4铁氧体粒子的平均直径约为20 nm.Ni0.4CoxZn0.6-xFe2O4在8.2~12.4 GHz的测试频率范围内具有介电损耗和磁损耗.在频率为9.0 GHz时,Ni0.4CoxZn0.6-xFe2O4(x=0.4)复介电常数虚部的最大值达到19.6.随着x值的增加,复数磁导率虚部的共振吸收峰向高频移动.制备的复合物可以被广泛地用于抑制电磁辐射和吸收雷达波等领域.     

Properties and performance of La1.6Sr0.4NiO4+δ-Ce0.8Sm0.2O1.9 composite cathodes for intermediate temperature solid oxide fuel cells

La_1.6Sr_0.4NiO_4+δ-Ce_0.8Sm_0.2O_1.9 composite cathodes were prepared successfully using combustion synthesis method for intermediate temperature solid oxide fuel cells. The chemical compatibility, thermal expansion behavior, electrical conductivity and electrode performance were studied. The X-ray diffraction of La_1.6Sr_0.4NiO_4+δ-Ce_0.8Sm_0.2O_1.9 composite result proved a slight reaction between La_1.6Sr_0.4NiO_4+δ and Ce_0.8Sm_0.2O_1.9. Both the thermal expansion coefficient and the electrical conductivity of La_1.6Sr_0.4NiO_4+δ-Ce_0.8Sm_0.2O_1.9 decreased with increasing Ce_0.8Sm_0.2O_1.9 content. AC impedance spectroscopy measurements indicated that the addition of 30 wt% Ce_0.8Sm_0.2O_1.9 to La_1.6Sr_0.4NiO_4+δ exhibited the lowest polarization resistance (0.238 Ωcm²) at 800 °C in air, which was only one fourth of the La_1.6Sr_0.4NiO_4+δ electrode measured at the same temperature.     

Synthesis, crystal stability, and electrical behaviors of La0.7Sr0.3Cr0.4Mn0.6O3?δ–XCu0.75Ni0.25 for its possible application as SOFC anode

La_0.7Sr_0.3Cr_0.4Mn_0.6O_3−δ (perovskite-type) nanocomposites impregnated with XCu_0.75Ni_0.25 have been synthesized by sol–gel method. Crystal structure of LSCM–Cu_0.75Ni_0.25 composites were refined by the Rietveld method. Crystal symmetry of CuO and NiO nanoparticles have monoclinic and cubic symmetry, respectively, but after sintering at 1,200 °C and reducing the temperature to 600 °C, it’s transformed into a new Cu_0.75Ni_0.25 intermetallic solid solution without secondary phase. We have detected a cationic inter-diffusion in Cu ↔ Ni interphase crystals during this reduction process; however, when sintering time exceeds 2 h at 1,200 °C this reaction mechanism is interrupted by a sublimation phenomenon; which causes Cu₂O cubic structure segregation from monoclinic CuO structure. This leads to Cu precipitation from the Cu_1−x Ni _x solid solution. Cu_0.75Ni_0.25 inhibits the LSCM perovskite-type grain growth (t ≈ 220 nm). Electrical conductivity indicates the presence of semiconductor and metallic-type behaviors with a maximum electrical conductivity (800 °C) >4.5 (log σ, Sm cm⁻¹). When Cu_0.75Ni_0.25 concentration was 25 and 35 %, semiconductor behavior were dominated. Thermal expansion coefficients showed a linear dependence inversely proportional to Cu_0.75Ni_0.25 concentration. Electrical conductivity, Rietveld analysis, Porosity, TEC, and E _a behaviors lead to the conclusion that the anodes between 25 and 35 % (Cu_0.75Ni_0.25) are closer to applications at SOFC.     

Effect of sintering temperature on the chemical bonding,electronic structure and electrical transport properties of β-Ga1.9Fe0.1O3 compounds

A model system,which is based on iron(Fe)doped gallium oxide(Ga₂O₃)(Ga_1.9Fe_0.1O₃),has been considered to elucidate the combined effect of transition-metal ion doping and processing temperature on the chemistry,local structure and chemical bonding,and electrical transport properties of a wide band gap oxide(Ga₂O₃).The Ga_1.9Fe_0.1O₃ compounds were synthesized using standard high-temperature solid state reaction method.The effect of processing conditions in terms of different calcination and sintering environments on the structural and electrical properties of Ga_1.9Fe_0.1O₃ compounds is studied in detail.Structural characterization by Raman spectroscopy revealed that Ga_1.9Fe_0.1O₃ compounds exhibit monoclinic crystal symmetry,which is quite similar to the intrinsic parental crystal structure,though Fedoping induces lattice strain.Sintering temperature(T_sint)which was varied in the range of 900-1200℃,has significant impact on the structure,chemical bonding,and electrical properties of Ga_1.9Fe_0.1O₃ compounds.Raman spectroscopic measurements indicate the proper densification of the Ga_1.9Fe_0.1O₃ compounds achieved through complete Fe diffusion into the parent Ga₂O₃ lattice which is evident at the highest sintering temperature.The X-ray photoelectron spectroscopy validates the chemical states of the constituent elements in Ga_1.9Fe_0.1O₃ compounds.The electrical properties of Ga_1.9Fe_0.1O₃ fully controlled by T_sint,which governed the grain size and microstructural evolution.The temperature and frequency dependent electrical measurements demonstrated the salient features of the Fe doped Ga₂O₃ compounds.The activation energy determined from Arrhenius equation is 0.5 e V.The results demonstrate that control over structure,morphology,chemistry and electrical properties of the Ga_1.9Fe_0.1O₃ compounds can be achieved by optimizing T_sint.     

La0.3Sr0.7Fe0.7Cu0.2Mo0.1O3-δ钙钛矿超细陶瓷粉体制备与催化性能研究

采用溶胶低温燃烧法制备了单一组成的La0.3Sr0.7Fe0.7Cu0.2Mo0.1O3-δ(LSFCM)超细钙钛矿陶瓷粉体。用XRD,SEM以及TA等方法对粉体的物相、形貌、粒度以及导电性能等进行了表征。考察了LSFCM陶瓷粉体对甲烷部分氧化(POM)制备合成气的催化活性与稳定性。结果表明:溶胶燃烧粉末经800℃下煅烧4h可得到平均粒径小于35nm的立方钙钛矿结构LSFCM陶瓷粉体,相对密度为96.7%的LSFCM烧结体在空气气氛600℃温度下电导率达到26.27S·cm-1,在950℃、CH4/O2比为1.5~2.0时,甲烷转化率及一氧化碳与氢气选择性均达到90.0%以上;反应43h后虽产生少量积炭,但仍能保持钙钛矿结构,表明LSFCM粉体对甲烷部分氧化制合成气反应具有良好的催化活性和稳定性。     

Ti0.4Zr0.1V1.1Mn0.5Ni0.4Crx（x=0,0.1,0.2,0.3）储氢合金的微观结构和电化学性能

采用XRD、SEM-EDS等方法对Ti0.4Zr0.1V1.1Mn0.5Ni0.4Crx(x=0,0.1,0.2,0.3)储氢合金的微观结构及电化学性能进行了表征。XRD分析结果表明Ti0.4Zr0.1V1.1Mn0.5Ni0.4Crx(x=0,0.1,0.2,0.3)储氢合金由BCC结构的V基固溶体主相和少量的C14Laves第二相组成。SEM-EDS分析结果表明,V基固溶体主相为树枝晶结构,C14Laves相呈网格状沿着主相晶界析出。电化学测试结果表明,Ti0.4Zr0.1V1.1Mn0.5Ni0.4Crx(x=0,0.1,0.2,0.3)氢化物电极在303K下,随Cr含量的增加,最大放电容量分别为574.6mAh/g、418.8mAh/g、368.8mAh/g和322.9mAh/g。当x=0.3时,合金电极在333K下的最大放电容量达到了824.1mAh/g。Cr的添加显著提高了合金电极的高倍率放电性能和循环寿命,40次充放电循环后Ti0.4Zr0.1V1.1Mn0.5Ni0.4Cr0.3合金电极的容量保持率为62.3%。     

Infrared and Structural Properties of Y1?xNdxBa2Cu3O7?δ (0 ≤ x ≤ 1)

Infrared and structural properties of Y_1–x Nd _x Ba₂Cu₃O_7– (0 x 1) were investigated using infrared absorption spectroscopy and X-ray powder diffraction. The unit cell parameters of the samples were defined using X-ray diffraction data. The resistance measurements showed that the samples revealed superconductivity in the temperature range of 80–100 K. It was observed that by the substitution of Nd to Y in YBa₂Cu₃O_{7 –} IR band at 573 cm^–1 that is assigned as Cu–O axial antisymmetric stretching mode shifts to 533 cm^–1 while the band at 620 cm^–1 that is due to Cu–O symmetric stretching mode in YBa₂Cu₃O_7– shifts to 588 cm^–1.     

Study on the Physical and Electrical Properties of Bi2 ? δZnδSr2Ca2Cu3O10 + y Glass-Ceramic Superconductors

We have fabricated a series of glass-ceramic (Bi_{2 –} Zn) Sr₂Ca₂Cu₃O_{10 + y} , where = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0, and investigated the effect of Zn ions on the glass formation, crystallization, thermal, electrical, and on the magnetic properties of the BSCCO-2223 superconductor system. The structural symmetry was found to be tetragonal in all the substitution levels. The best electrical performance was obtained from the = 0 sample, the T _c and T _zero was obtained at 110 K and 107 K, respectively. The J _c values of the samples were determined using the magnetization hysteresis and Bean's model. The crystallization kinetics were investigated using nonisothermal models of Augis–Bennett. The calculated activation energy, E _a, of the system was found to be in the range of 258–336 kJ/mol.     

LaNi0.6Fe0.4O3阴极接触材料导电特性调控及其对SOFC电化学性能的影响

鉴于平板式固体氧化物燃料电池(SOFC)电堆对低面电阻、高稳定性阴极接触材料的需求,本研究阐明了LaNi_0.6Fe_0.4O₃(LNF)颗粒尺寸调控对导电和SOFC单电池性能演变的影响机制,优化了LNF预处理工艺,降低了接触组件面电阻,提升了SOFC单电池性能及热循环稳定性。结果表明：预压造粒的样品(LNF-2)与高温烧结预处理的样品(LNF-3)的面电阻更小,分别为0.074和0.076?·cm²;在750℃施加1 A/cm²电流负载后,能够更快地进入稳态,并保持颗粒尺寸稳定。其中,LNF-2单电池在750℃下的峰值功率密度0.94 W/cm²较未处理的LNF的0.66 W/cm²高,但在热循环过程中性能衰减较大,下降了20%;而LNF-3单电池在20次热循环后峰值功率密度仅下降了4%。本研究对高可靠SOFC电堆装配及其长寿命稳定运行具有指导及参考价值。