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  • 1
    Electronic Resource
    Electronic Resource
    Protonic and oxygen-ion conduction in SrZrO3-based materials (1995)
    Springer
    Journal of materials science 30 (1995), S. 2785-2792 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00349644
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  • 2
    Electronic Resource
    Electronic Resource
    La2Zr2O7 formed at ceramic electrode/YSZ contacts (1993)
    Springer
    Journal of materials science 28 (1993), S. 3809-3815 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00353183
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  • 3
    Electronic Resource
    Electronic Resource
    p-type conductivity in gadolinia-doped ceria (1996)
    Springer
    Journal of materials science 15 (1996), S. 1716-1718 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00636205
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  • 4
    Electronic Resource
    Electronic Resource
    Role of water vapour pressure on the electrical conductivity of La0.9Sr0.1GaO3 (1997)
    Springer
    Journal of materials science 17 (1997), S. 75-77 
    Details
    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
    URL: http://dx.doi.org/10.1023/A:1006558111343
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  • 5
    Electronic Resource
    Electronic Resource
    Performance of YSZ oxygen sensors protected by electrochemical filters (1995)
    Springer
    Ionics 1 (1995), S. 125-130 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02388669
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  • 6
    Electronic Resource
    Electronic Resource
    Observation of ionic thermocurrents in zirconia-based solid electrolytes (1995)
    Springer
    Ionics 1 (1995), S. 377-383 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02375279
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  • 7
    Electronic Resource
    Electronic Resource
    Protonic conduction in substoichiometric SrZrO3-based ceramics (1995)
    Springer
    Ionics 1 (1995), S. 443-447 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02375289
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  • 8
    Electronic Resource
    Electronic Resource
    Degradation of zirconia based oxygen sensors in glass melting furnaces (1996)
    Springer
    Ionics 2 (1996), S. 12-18 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02375862
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  • 9
    Electronic Resource
    Electronic Resource
    On the accuracy of oxygen pressure measurements (2000)
    Springer
    Ionics 6 (2000), S. 22-29 
    Details
    ISSN: 1862-0760
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Zirconia-based oxygen sensors are used in many applications and in research. However, the measurement of oxygen partial pressures with these devices is not necessarily correct. Reasons for deviation between sensor reading and nominal composition of the gas mixture are reviewed in this work. The sensor electrochemical permeability is introduced as a starting point. The impact of this oxygen leak on the composition of the surrounding atmosphere is evaluated from mass balances to all species in the system. This procedure shows that even the use of mixtures like CO+CO2 to establish a given oxygen partial pressure has a limited range of applicability. This is due to the small buffer behavior of some of these mixtures. The gas phase transport of oxygen away from the sensor electrode is also studied. High concentration overpotentials are expected to develop under the circumstances where the buffer behavior of the gas mixture is small. In fact, high concentrations of the CO/CO2 couple are required both to optimize the gas-mixture buffer effect and the oxygen transport in the gas phase. The latter instead of consisting exclusively of simple diffusion of free oxygen molecules might also involve combined diffusion and counter diffusion of both carbon oxides as oxygen carriers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02375544
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  • 10
    Electronic Resource
    Electronic Resource
    Electrode processes of LaCoO3+La2Zr2O7 cathodes deposited onto GCO (2000)
    Springer
    Ionics 6 (2000), S. 260-266 
    Details
    ISSN: 1862-0760
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A combination of dc and ac results was used to study the electrode processes of LaCoO3+La2Zr2O7 cathodes deposited onto a GCO electrolyte, in air and in the range 600–800 °C. Steady state polarisation results showed that the overpotential values are very dependent on the electrode microstructures, which might be optimised by changes in the deposition and/or firing conditions of the electrodes. Tafel plots suggest different mechanisms under low and relatively high cathodic polarisation, with a transition at about −0.2 V at 700 °C. The transition tends to be displaced towards higher cathodic overpotentials with decreasing temperatures. The exchange current density is higher in the high polarisation regime (high values of |η|) than under low polarisation, and the exchange coefficient is lower in the range of high |η| The changes in pseudocapacitance and electrode resistance extracted from ac results also indicate a change in the regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02374075
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