Crystal Structure–Ionic Conductivity Relationships in Doped Ceria Systems

In the past, it has been suggested that the maximum ionic conductivity is achieved in ceria, when doped with an acceptor cation that causes minimum distortion in the cubic fluorite crystal lattice. In the present work, this hypothesis is tested by measuring both the ionic conductivity and elastic lattice strain of 10 mol% trivalent cation-doped ceria systems at the same temperatures. A consistent set of ionic conductivity data is developed, where the samples are synthesized under similar experimental conditions. On comparing the grain ionic conductivity, Nd_0.10Ce_0.90O_2−δ exhibits the highest ionic conductivity among other doped ceria systems. The grain ionic conductivity is around 17% higher than that of Gd_0.10Ce_0.90O_2−δ at 500°C, in air. X-ray diffraction profiles are collected on the sintered powder of all the compositions, from room temperature to 600°C, in air. From the lattice expansion data at high temperatures, the minimal elastic strain due to the presence of dopant is observed in Dy_0.10Ce_0.90O_2−δ. Nd_0.10Ce_0.90O_2−δ exhibits larger elastic lattice strain than Dy_0.10Ce_0.90O_2−δ with better ionic conductivity at intermediate temperatures. Therefore, it is shown that the previously proposed crystal structure–ionic conductivity relationship based on minimum elastic strain is not sufficient to explain the ionic conductivity behavior in ceria-based system.     

增塑剂对聚氨酯型固体电解质离子导电性能的影响

利用溶液聚合方法合成了聚醚聚氨酯,并以聚氨酯、高氯酸锂和增塑剂为组分,制备了一系列新型聚合物固体电解质。运用差示扫描量热分析、动态力学分析、交流复阻抗谱、扫描电镜和原子力显微镜对体系性能和形态进行了研究。结果表明,在聚氨酯/高氯酸锂复合物中,增塑剂的加人会导致体系玻璃化转变温度和力学性能有所下降,离子导电性能显著增加。在所研究的6种增塑剂碳酸丙烯酯、碳酸二乙酯、二乙二醇二甲醚、N,N-二甲基甲酰胺、聚乙二醇400和丙三醇中,聚乙二醇400对聚氨酯/高氯酸锂复合物的增塑效果最好,该体系室温电导率达到10-4S／cm。     

Thermal Conductivity: XII, Temperature Dependence of Conductivity for Single-Phase Ceramics

Theoretical relationships and experimental data concerning thermal conductivity for a number of oxide materials have been compared over a wide temperature range. Deviations from the basic proportionality between k and 1/ T are caused by radiant-energy transmission, a high Debye temperature, a low mean free path of the thermoelastic waves, porosity, and in a few cases electronic conductivity. Extrapolation of thermal conductivity data to high temperatures is not reliable.     

Electronic Conductivity of La-Doped Ceria Ceramics

Lanthanum-doped ceria powder with a composition Ce_0.8La_0.2O_1.9 was prepared by heating the oxalate solid solution (Ce_0.8La_0.2)₂(C₂O₄)₃ at 873 K in air. As-prepared powder was densified to 96%–97% relative density by sintering in air at 1773 K for 4 h. The electronic current of the disk sample was measured in a temperature range from 773 to 1113 K by the direct current polarization method using a Hebb–Wagner ion-blocking cell. A linear relationship, which was theoretically predicted, was measured between log σ_e (electronic conductivity) and E (applied voltage) in the applied voltage range of 0.2–1.0 V. The σ_e was proportional to P _O2^−1/4.3≈ P _O2^−1/4.6 in the oxygen partial pressure range of 10⁻²–10⁻⁸ Pa, and to P _O2^−1/6.7≈ P _O2^−1/7.1 in the oxygen partial pressure range of 10^−7.5–10⁻²² Pa. The apparent activation energy of the electronic conduction was 1.87–1.94 eV. The hole conduction was also measured in the P o₂ range of 10²–10⁵ Pa. The transport number of oxide ion was 0.96–1.00 at 773–1113 K under an oxygen partial pressure of 10⁻⁵ Pa.     

铝电解质体系初晶温度、密度和电导率

采用先进的实验技术测定了Na3AlF6-AlF3-Al2O3-CaF2-LiF-NaCl系电解质的初晶温度、密度和电导率. 首先提供了测量的实验数据,接着基于实验数据给出了该体系的初晶温度、密度和电导率的计算公式,并与以前的经验公式作对比,最后从理论上分析了AlF3, Al2O3, LiF和NaCl对电解质物理化学性质的影响. 实验表明,LiF和NaCl能够有效地降低铝电解质的初晶温度并能提高电导率,是十分优良的添加剂,两者配合使用效果良好. 本工作旨在探索新型低温铝电解质组成,为铝电解工业选择适宜的电解质成分提供科学的理论依据.     

聚氧化乙烯-蒙脱土复合聚合物电解质室温电导率的研究

采用溶液浇铸法对蒙脱土与聚氧乙烯、LiClO4进行复合制备了聚合物电解质膜。用X射线衍射对蒙脱土及电解质膜进行了结构表征。采用交流阻抗法对复合型电解质膜的离子电导率进行了测试。结果表明：一定量的蒙脱土可以使（PEO）16LiClO4的离子电导率提高几倍。蒙脱土对基体离子电导率提高程度的不同取决于蒙脱土的含量。     

Temperature Dependence of the Thermal Diffusivity/Conductivity of Aluminum Nitride

The temperature dependence of the thermal conductivity of a polycrystalline AIN was measured using the flash-diffusivity technique over a range of experimental conditions. Thermal conductivity data from room temperature to 300°C, obtained with attenuated laser pulse energies to minimize the specimen temperature increase, were found to be inversely proportional to the absolute temperature, as expected from theory. For high pulse energies, the experimental data deviated significantly from expected behavior. This latter effect is offered as an explanation for the anomalously low temperature dependence for the thermal conductivity reported in the literature.     

Temperature Dependence of the Conductivity in Ceramic Materials Containing Nickel Nanoparticles

We have measured and analyzed the temperature dependence of the conductivity of composites in which nickel nanoparticles are embedded in an insulating matrix. Observing a transition from a variable-range hopping to a near-neighbor hopping, with increasing temperature, is suggested to correspond to the microscopically observed transition from a homogeneous-like to a percolation-like electrical network.     

CeO_2基电解质材料的扫描电镜观察

用Ｓｍ ２Ｏ３和Ｇｄ２Ｏ３共同掺杂ＣｅＯ２基电解质组分（ＣｅＯ２）０９（Ｓｍ ２Ｏ３）００５（Ｇｄ２Ｏ３）００５随着烧结温度的提高,晶粒持续长大,由１４００℃烧结时的２～３μｍ 长大到１６００℃烧结时的１０～１２μｍ ,单位尺寸内的晶界数量减少;各温度烧结样品的断口都呈穿晶断裂。ＣｅＯ２基电解质可以在１４００～１４５０℃烧结并获得较高电导率：８００℃时约为７Ｓｍ － １．随着烧结温度的提高,电导率下降,这可能是由于晶间玻璃相的增多造成的。     

Ionic Conductivity and Power Conversion Efficiency Study of KI Incorporated Glucosyl Carboxonium Ion-based Biopolymer Crust Electrolyte

The impedance of well-characterized KI-incorporated glucosyl carboxonium ion-based biopolymer crust electrolytes up to a maximum 2.7?wt% was measured using electrical impedance spectroscopy. Enhanced ionic conductivity of 2.3657?×?10^?2?S?cm^?1 on the addition of 2.7?wt% of KI was observed in contrast to earlier reported value for pure GCI of 4.5278?×?10^?4?S?cm^?1. This is attributed due to the increased concentration of KI in the system and is corroborated with increased ion density (n), mobility (µ), and diffusion coefficients (D). Dielectric and modulus study shows the capacitive nature of electrolyte. Fabricated dye-sensitized solar cell using pure glucosyl carboxonium ion crust and KI-incorporated glucosyl carboxonium ion crust shows the efficiency of 1.19% for pure and shows the efficiency of 2.14% for 2.6?wt% of KI in glucosyl carboxonium ion at 1 sun condition.     

Potential, Temperature and Doping Dependence for Macropore Formation on n-Si with Backside-Illumination

Applying an anodic bias on a silicon HF contact and illuminating the backside of a n-type silicon wafer allows to create macropores. The formation of random macropores is studied in this paper by determination of the influences of the potential, the temperature and the doping level. A statistical approach is used to evaluate the micrographs. The formation of the macroporous layer consists of two phases. Beginning with a plane surface and homogeneous dissolution of silicon, first pores occur after some time. In this nucleation phase the thickness of the homogeneously dissolved Si depends strongly on the doping level and the temperature but only weakly on the applied bias. In a second phase of stable pore growth the density of pores is investigated as a function of temperature and anodic potential. For low doped material we find a strong stabilisation influence of the deep space charge region (SCR) in the nucleation as well as in the stable pore growth phase. Thus an increased anodic bias decreases the density of pores. For highly doped silicon no stabilisation influence of the SCR is found. The pore growth is dominated by the electrochemical dissolution rate, i.e. increasing the potential increases the density of the macropores.     

Electrochemical Stability of Strontium-Doped Ceria Electrolyte in Solid-Oxide Fuel Cell Applications

SrO-doped CeO₂ electrolyte has been evaluated in single-cell configuration under solid-oxide fuel cell operating conditions. Because of oxygen loss from the crystal lattice, the material experiences a macroscopic expansion of several percent at 1000°C. On extended cell operation, strontium precipitates-out at/near the anode, resulting in irreversible cell degradation in the case of SrO-doped CeO₂. Precipitation and diffusion of SrO causes decreased ionic conductivity and may result in anode delamination. SrO precipitation is attributed to insolubility of the dopant in the reduced CeO₂ phase. The diffusion of strontium seems to be related to the flux of oxygen through the sample, but an exact mechanism is unknown.     

优化循环冷却水系统提高循环水浓缩倍数

制药单位循环水系统的有效运行是一项较复杂的系统工程.综合分析了石药集团河北中润制药有限公司循环水系统的一次水用量规律,介绍了如何在生产中提高循环水站浓缩倍数、降低一次水用量的系统优化措施,总结了取得的节能效益.     

室温离子液体1-丁基-3-甲基咪唑磷酸二丁酯的电导率研究

利用磷酸三丁酯与N-甲基咪唑在恒温150℃下一步合成了离子液体1-丁基-3-甲基咪唑磷酸二丁酯,考察了其在丙酮,水,DMF,乙酸溶剂中的电导率及摩尔电导率。实验发现该离子液体在不同溶剂中的电导率(κ)相差很大,其顺序为κa(水)>κb(DMF)>κc(丙酮)>κd(乙酸)。在相同温度下,电导率及摩尔电导率随浓度的增大而增大;在相同浓度下,电导率及摩尔电导率随温度的升高而增大。     

Structure and Ionic Mobility of Zirconia at High Temperature

The high-temperature structure of zirconia was studied by powder neutron diffraction up to 2400°C. The boundaries of the domain of the nonstoichiometric tetragonal form are defined. They are consistent with a tetragonal-cubic transition at 2350°C for stoichiometric zirconia. The changes in the structural parameters of the tetragonal form (unit-cell, positional parameters and thermal B factors) with temperature give evidence of medium zirconium and oxygen mobilities. The oxygen ions are, however, always more mobile than the zirconium ions. An enhancement with temperature of the structural an-isotropy tends to weaken the weaker of the two distinct Zr-0 bonds of the tetragonal zirconia. It results in the transformation into the cubic form which is accompanied by a change in unit-cell volume; this change becomes sharper as the composition tends toward stoichiometry. This transition is probably followed by an increase of the ionic mobility.     

Fabrication and Characterization of Anode‐Supported Low‐Temperature SOFC Based on Gd‐Doped Ceria Electrolyte

Large‐size, 9.5 cm × 9.5 cm, Ni‐Gd_0.1Ce_0.9O_1.95 (Ni‐GDC) anode‐supported solid oxide fuel cell (SOFC) has been successfully fabricated with NiO‐GDC anode substrate prepared by tape casting method and thin‐film GDC electrolyte fabricated by screen‐printing method. Influence of the sintering shrinkage behavior of NiO‐GDC anode substrate on the densification of thin GDC electrolyte film and on the flatness of the co‐sintered electrolyte/anode bi‐layer was studied. The increase in the pore‐former content in the anode substrate improved the densification of GDC electrolyte film. Pre‐sintering temperature of the anode substrate was optimized to obtain a homogeneous electrolyte film, significantly reducing the mismatch between the electrolyte and anode substrate and improving the electrolyte quality. Dense GDC electrolyte film and flat electrolyte/anode bi‐layer can be fabricated by adding 10 wt.% of pore‐former into the composite anode and pre‐sintering it at 1,100 °C for 2 h. Composite cathode, La_0.6Sr_0.4Fe_0.8Co_0.2O₃, and GDC (LSCF‐GDC), was screen‐printed on the as‐prepared electrolyte surface and sintered to form a complete single cell. The maximum power density of the single cell reached 497 mW cm^–2 at 600 °C and 953 mW cm^–2 at 650 °C with hydrogen as fuel and air as oxidant.     

锂电池离子液体电解质的研究进展

离子液体具有电导率高、热稳定性好、无污染、蒸气压极低等特性,是非常有希望应用于锂电池或电化学电容器的电解质。本文介绍了离子液体电解质体系在锂电池中的研究以及聚合物电解质一离子液体体系的研究进展。     

Preparation and Characterization of Samaria-Doped Ceria Electrolyte Materials for Solid Oxide Fuel Cells

The microstructure, thermal expansion, mechanical property, and ionic conductivity of samaria-doped ceria (SDC) prepared by coprecipitation were investigated in this paper. The results revealed that the average particle size ranged from 10.9±0.4 to 13.5±0.5 nm, crystallite dimension varied from 8.6±0.3 to 10.7±0.4 nm, and the specific surface area distribution ranged from 62.6±1.8 to 76.7±2.2 m²/g for SDC powders prepared by coprecipitation. The dependence of lattice parameter, a, versus dopant concentration, x , of Sm³⁺ ion shows that these solid solutions obey Vegard's rule as a ( x )=5.4089+0.10743 x for Ce_{1− x} Sm _x O_{2−1/2 x} . For SDC ceramics sintered at 1500°C for 5 h, the bulk density was over 95% of the theoretical density; the maximum ionic conductivity, σ_800°C=(22.3±1.14) × 10⁻³ S/cm with minimum activation energy, E _a=0.89±0.02 eV, was found in the Ce_0.80Sm_0.20O_1.90 ceramic. A dense Ce_0.8Sm_0.2O_1.9 ceramic with a grain size distribution of 0.5–4 μm can be obtained by controlling the soaking time at 1500°C. When the soaking time was increased, the microhardness of Ce_0.8Sm_0.2O_1.9 ceramic increased, the toughness slightly decreased, which was related to grain growth with the soaking time.