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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 17 (1997), S. 75-77 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 15 (1996), S. 1716-1718 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 30 (1995), S. 2785-2792 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Strontium zirconate-based materials have been studied as potential high-temperature protonic conductors. Yttrium for zirconium substitution, and lanthanum for strontium substitution were selected to demonstrate that changes in composition can be used as a tool to design the properties. At temperatures below about 900 ° C, both yttrium-doped and undoped strontium zirconate are mostly protonic conductors at oxygen partial pressures below about 1 Pa, and mixed ionic and p-type conductors at higher pressures. The main ionic contribution changes from mostly protonic to oxygen-ion conduction with increasing temperature, which may affect the performance of electrochemical devices. Yttrium for zirconium substitution enhances both the electronic and ionic conductivities. Lanthanum for strontium substitution suppresses protonic conduction and gives rise to mixed oxygen-ion and n-type conduction in reducing conditions.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 28 (1993), S. 3809-3815 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Strontium-doped LaCoO3 or LaMnO3 materials have been studied for use as cathodes for solid oxide fuel cells (SOFCs). This choice relies on the required properties and competitive cost. However, formation of reaction products under typical electrode-firing conditions may affect the performance of SOFCs. La2Zr2O7 was detected at YSZ/electrode interfaces. This reaction product was synthesized from powders and characterized to obtain a better understanding of its effects on cell performance. Its structural, thermal, and electrical properties are reported.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Ionics 1 (1995), S. 443-447 
    ISSN: 1862-0760
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The transport properties of strontium zirconate based materials were investigated using different characterization techniques. The electrical conductivity is mainly protonic below 610°C, while the contribution of electron holes increases with temperature and oxygen partial pressure. Under extreme reducing conditions, the conductivity is dominated by protons and oxygen ions. Polarization results are consistent with the results obtained.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1862-0760
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Oxygen sensors based on YSZ (yttria stabilized zirconia) are best known for high temperature measurements. The protection of such oxygen sensors with dense electrochemical filters is an effective way to increase their life time in aggressive industrial atmospheres. This work reports on the performance of sensors protected by composite or single phase mixed conducting filters. The first group includes materials based on GCO (Gd2O3 doped CeO2)+LC (LaCoO3), and on YSZ+LCM (La(Mn,Co)O3). Sensors protected with GCO+LC composites showed the best performance amongst the composite filters already evaluated. Electroded single phase GCO filters were also tested to check on the role of surface reaction kinetics on the overall oxygen transport process across the filter. The fastest sensor responses to a sudden decrease in oxygen partial pressure were obtained with deposited electrodes either on both surfaces of the filter or on the filter cathode side. These preliminary results suggest that the cathodic process is more relevant than the anodic one in determining the filter permeability (and protected sensor performance), which fulfils the logical requirement of electrode free surfaces in contact with the furnace atmosphere.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1862-0760
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Oxygen ion conduction in La0.9Sr0.1Ga1−xMxO3−δ (M=Cr, Fe; x=0 – 0.20), LaGa1−xMxO3−δ (M=Co, Ni; x=0.20 – 0.60), LaGa1−x−yCoxMgyO3−δ (x=0.35 – 0.60; y=0.10 – 0.25) and LaGa0.85−xMg0.15(Nb0.33Mg0.66)xO3−δ (x=0 – 0.20) is reported. At temperatures below 1200 K the ionic conductivity of La(Ga,M)O3−δ (M=Co, Ni) increases with increasing oxygen nonstoichiometry, but is lower than for La(Ga,Mg)O3−δ and (La,Sr)GaO3−δ. Co-doping with Nb and Mg was found to result in decreasing ionic transport in La(Ga,Nb,Mg)O3−δ due to blocking of oxygen sites by Nb5+. Small additions of Fe to the B-site of La0.9Sr0.1GaO3−δ increase the ionic conductivity, whereas substitution of Cr for Ga has the opposite effect. Incorporation of transition metal cations into the Ga site leads to a higher p-type electronic conductivity in all studied perovskites.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Ionics 1 (1995), S. 125-130 
    ISSN: 1862-0760
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The performance of nernstian Yttria Stabilized Zirconia (YSZ) oxygen sensors can be seriously affected when in contact with some aggressive industrial furnace atmospheres. Longer life time can be obtained for sensors protected with electrochemical filters. The most relevant parameters determining the protected sensor performance are the ratio between the sensor and the filter oxygen electrochemical permeabilities, and the volume of the electrode protection chamber. The ratio between materials electrochemical permeabilities determines the sensor oxygen activity applicability domain and the deviation between the effective (steady state) and desirable (theoretical) sensor reading. The protected chamber volume will influence the time response behavior. Theoretical predictions on sensor performance are compared with experimental data obtained for protected YSZ sensors conceived for moderately oxidizing atmospheres (1 Pa〈Po2〈21 kPa). Two different cases are studied including one single phase and one composite (ionic + electronic conductor) electrochemical filter.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1862-0760
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In ionic conductors, long range-migrating charges are a main cause of polarization processes. This has complicated, up to date, the study of ionic thermocurrents (ITC) in solid electrolytes. However, the method is appealing, as it probes directly charge-formation phenomena that are important both from a scientific point of view and for applications. This work reports on the observation of ITC in solid electrolytes. Under appropriate experimental conditions, the ITC response of a zirconia sample electroded with platinum is a reproducible one, thus opening the way to a new characterization method that may complement other well established methods, such as Impedance Spectroscopy and a number of electrochemical techniques. The general trends of the response, which is composed of two well resolved ITC peaks, is discussed. One of them, taking place at higher temperatures, conforms to the standard shape of a first order kinetics depolarization process.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1862-0760
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract To study the result of an intimate glass-ceramic contact, mixtures (up to 5 weight%) of a soda-lime glass with two different ceramic electrolytes were fired at 1400 and 1500°C. Yttria stabilized zirconia (YSZ) and tetragonal polycrystalline zirconia (TZP) were the selected electrolytes. Microstructural observations and impedance spectroscopy measurements performed in air between 300 and 800°C were used for the characterization of these ceramic-glass composites. The higher the glass content in the sample the higher the intermediate frequency impedance contribution, exceeding at least by one order of magnitude the values observed for grain boundaries in the pure electrolyte compositions. The high frequency arc was found less dependent on the amount of added glass. Sintered samples based on YSZ were found to accommodate glass better than TZP, as confirmed by the comparatively modest intermediate frequency impedance contribution always observed with the first material for any given amount of added glass. Alumina additions (10 weight%) to the electrolyte-glass composites were found quite effective in decreasing this intermediate frequency contribution, suggesting that zirconia-alumina composites might exhibit enhanced corrosion resistance when in contact with glass melts.
    Type of Medium: Electronic Resource
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