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Claude Delmas - One of the best experts on this subject based on the ideXlab platform.
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Improvement by heating of the Electronic Conductivity of cobalt spinel phases, electrochemically synthesized in various electrolytes
Journal of Solid State Chemistry, 2009Co-Authors: Myriam Douin, Lionel Goubault, Michel Menetrier, Emilie Bekaert, Patrick Bernard, Liliane Guerlou-demourgues, Claude DelmasAbstract:The nature of the alkaline electrolyte (based on KOH, NaOH, LiOH), in which Co3O4 spinel type phases are synthesized by electrooxidation of CoO, is shown to play a key role on the composition, the structure and the Electronic Conductivity of the materials. In the materials, prepared in pure LiOH electrolyte or in mixed ternary electrolyte (KOH, NaOH, LiOH), Co4+ ions are present in the octahedral framework, which entails Electronic delocalization in the cobalt T2g band and a high Conductivity. The structure of the sample, synthesized in KOH, is on the opposite closer to that of ideal Co3O4, with only Co3+ in the octahedral sublattice, which leads to a semi-conducting behavior. Whatever the initial material, a thermal treatment induces an increase of the Co4+/Co3+ ratio in the octahedral network, resulting in a significant increase of the Electronic Conductivity.
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Improvement by heating of the Electronic Conductivity of cobalt spinel phases, electrochemically synthesized in various electrolytes
Journal of Solid State Chemistry, 2009Co-Authors: Myriam Douin, Lionel Goubault, Michel Menetrier, Emilie Bekaert, Patrick Bernard, Liliane Guerlou-demourgues, Claude DelmasAbstract:The nature of the alkaline electrolyte (based on KOH, NaOH, LiOH), in which Co{sub 3}O{sub 4} spinel type phases are synthesized by electrooxidation of CoO, is shown to play a key role on the composition, the structure and the Electronic Conductivity of the materials. In the materials, prepared in pure LiOH electrolyte or in mixed ternary electrolyte (KOH, NaOH, LiOH), Co{sup 4+} ions are present in the octahedral framework, which entails Electronic delocalization in the cobalt T{sub 2g} band and a high Conductivity. The structure of the sample, synthesized in KOH, is on the opposite closer to that of ideal Co{sub 3}O{sub 4}, with only Co{sup 3+} in the octahedral sublattice, which leads to a semi-conducting behavior. Whatever the initial material, a thermal treatment induces an increase of the Co{sup 4+}/Co{sup 3+} ratio in the octahedral network, resulting in a significant increase of the Electronic Conductivity. - Graphical abstract: In 'Co{sub 3}O{sub 4}' type spinel phases synthesized by eleectrooxidation, the nature of the alkaline electrolyte allows to monitor the amounts of hydrogen and lithium, inserted in spinel framework and therefore the Electronic Conductivity. Whatever the initial synthesis electrolyte, a moderate thermal treatment of the materials induces a significant increase ofmore » the Electronic Conductivity, due to a structural reorganization (illustrated by the evolution of the cell parameter) and an increase of the Co{sup 4+}/Co{sup 3+} ratio in the octahedral framework.« less
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effect of thermal treatment on the Electronic Conductivity properties of cobalt spinel phases synthesized by electro oxidation in ternary alkaline electrolyte koh lioh naoh
Chemistry of Materials, 2008Co-Authors: Myriam Douin, Lionel Goubault, Liliane Guerloudemourgues, Michel Menetrier, Emilie Bekaert, Patrick Bernard, Claude DelmasAbstract:A thermal treatment of Co3O4 type spinel phases, synthesized by electrooxidation of CoO powder in a mixed alkaline electrolyte (KOH, LiOH, NaOH), is shown to have an important influence on the Electronic Conductivity properties of the materials. The initial spinel phase contains hydrogen, lithium, cobalt vacancies, and especially Co4+ ions within the structure, leading to an Electronic Conductivity significantly larger than that of stoichiometric Co3O4. The thermal treatment, followed by in situ X-ray diffraction, TGA-MS and Electronic Conductivity measurements, induces a water release, coupled with an increase of the Co/O atomic ratio and a structural reorganization. The resulting cationic redistribution within the spinel framework entails an increase of the Co4+ amount in the [Co2O4] network and therefore of the Electronic Conductivity (by 3 orders of magnitude).
Harumi Yokokawa - One of the best experts on this subject based on the ideXlab platform.
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Electronic Conductivity and Efficiency of SOFC Electrolytes
ECS Transactions, 2019Co-Authors: Katsuhiko Yamaji, Yueping Xiong, Haruo Kishimoto, Teruhisa Horita, Manuel E. Brito, Harumi YokokawaAbstract:Relatively high Electronic Conductivity of SOFCs' electrolytes significantly decrease the energy conversion efficiency on power generation. This feature was confirmed especially for LSGMC and GDC electrolytes. The effect of electron Conductivity on the efficiency for GDC electrolyte was very sensitive to fuel utilization rate. The efficiency increases with fuel utilization rate because the oxygen partial pressure in the fuel increases with fuel utilization rate and the Electronic Conductivity decreased with increasing the oxygen partial pressure.
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Electronic Conductivity of Scandia-Stabilized Zirconia Doped with 1 mol% CeO2
ECS Transactions, 2012Co-Authors: Taro Shimonosono, Haruo Kishimoto, Katsuhiko Yamaji, Teruhisa Horita, Manuel E. Brito, Mina Nishi, Harumi YokokawaAbstract:Scandia-stabilized zirconia (ScSZ) has been extensively studied for the application to solid oxide fuel cells (SOFCs) because of its higher oxide ion Conductivity compared to conventional yttria-stabilized zirconia (YSZ). The Electronic Conductivity of ScSZ is significantly lower than the ionic Conductivity but is important to determine the performance of SOFC materials. In the case of nickel – stabilized zirconia cermet anode, when the scandiastabilized zirconia was used, the durability against methane fuel was enhanced [1]. The minor carriers like electron and proton in ionic conductor may affect the reaction mechanism at the cermet anode as proposed in literature [2]. ScSZ with 10 mol% Sc2O3 has the highest ionic Conductivity among different content of Sc2O3 at 1273 K [3] and is generally doped with 1 mol% CeO2 to suppress the transformation of cubic to rhombohedral phase [4]. Since the valence state of cerium ion varies from 4+ to 3+ with decreasing oxygen partial pressure (p(O2)), the concentration of electron carrier in ScSZ would be affected by doping with CeO2 if the electrons on the trivalent Ce ions behave as carrier (CeZr+1/2OO Ce’Zr+1/2VO+1/4O2). In our previous study on the Electronic Conductivity of [(CeO2)x(ZrO2)1x]0.8(YO1.5)0.2 solid solution [5], it was observed that the Electronic Conductivity of the solid solution with CeO2 content of x 0.1 was 4 – 5 order-of-magnitude larger than that of x = 0, and that the Electronic Conductivity of solid solution with CeO2 had unusual p(O2) dependency like the concentration product of trivalent and tetravalent Ce ions. In this study, the Electronic Conductivity of 10 mol% Sc2O3-stabilized ZrO2 doped with 1 mol% CeO2 (1Ce10ScSZ) was measured using a modified HebbWagner ion blocking cell reported elsewhere [6]. The contribution of 1 mol% CeO2 to the Electronic conduction of ScSZ was investigated by clarifying the p(O2) and temperature dependence of Electronic Conductivity of 1Ce10ScSZ. Figure 1 shows the Electronic Conductivity of 1Ce10ScSZ at 1173 – 1273 K in the p(O2) range of 10 – 10 MPa. At p(O2) > 10 MPa, the Electronic Conductivity at 1273 K was proportional to the 1/4 power of p(O2). The 1/4 power dependence was also observed at 1173 K in p(O2) > 10 MPa. Such 1/4 power dependence is usually explained by the p(O2) dependence of Electronic hole concentration which is derived from the hole formation reaction (1/2VO +1/4O2 h + 1/2OO). At p(O2) > 10 MPa, the Electronic Conductivity at 1273 K was proportional to the -1/4 power of p(O2), which is usually interpreted as the p(O2) dependence of electron concentration which is derived from the electron formation reaction (1/2OO e’ + 1/2 VO +1/4O2). The solid line in fig. 1 shows the fitting curve of measured Conductivity data with following equation, e = h[p(O2) / 0.1MPa] + e[p(O2) / 0.1MPa] (1) where h and e are constants. In the p(O2) range of 10 – 10 MPa, the p(O2) dependence of Electronic Conductivity at 1273 K deviated from the 1/4 and -1/4 power law expressed in eq. (1). The upper deviation of Electronic Conductivity from the 1/4 and -1/4 power law is attributed to the increase of electron concentration due to the reduction of doped CeO2. It is meaning that the electron on trivalent Ce ion behaves as electron carrier. Because of the limited amount of Ce dopant (1 mol%), the -1/4 power dependence due to the ZrO2 matrix appeared at lower p(O2) (< 10 MPa). To investigate the contribution of 1 mol% CeO2 to the Electronic conduction of ScSZ in detail, the Electronic Conductivity of 1Ce10ScSZ is measured at 1173 K in the lower p(O2) region.
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Electronic Conductivity of Ni-doped yttria-stabilized zirconia
Solid State Ionics, 2012Co-Authors: Taro Shimonosono, Haruo Kishimoto, Katsuhiko Yamaji, Teruhisa Horita, Manuel E. Brito, Harumi YokokawaAbstract:Abstract The Electronic Conductivity of (NiO) 0.01 [(Y 2 O 3 ) 0.08 (ZrO 2 ) 0.92 ] 0.99 was measured with a modified ion blocking method at 1273 K in the oxygen partial pressure ( p (O 2 )) range of 10 − 3 –10 − 17 MPa. At p (O 2 ) > 10 − 6 and − 14 MPa, the Electronic Conductivity was proportional to the 1/4 and − 1/4 power of p (O 2 ) due to hole and electron conduction, respectively. The electron Conductivity was obviously smaller for Ni-doped YSZ than for YSZ by a factor of 2.0 at p (O 2 ) range of 10 − 14 –10 − 17 MPa. The measured Electronic Conductivity of Ni-doped YSZ was used to calculate the oxygen potential distribution in the electrolyte under the ion blocking condition. The lower oxygen potential region in the electrolyte was in excellent agreement with the darkly colored region found in the Ni-doped YSZ electrolyte after the Electronic Conductivity measurements.
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Electronic Conductivity of pure ceria
Solid State Ionics, 2011Co-Authors: Yueping Xiong, Haruo Kishimoto, Katsuhiko Yamaji, Masashi Yoshinaga, Teruhisa Horita, Manuel E. Brito, Harumi YokokawaAbstract:Abstract The Electronic Conductivity of pure ceria with two different impurity levels is examined by dc polarization technique based on the Hebb–Wagner ion blocking method. The impurity level for the ceria with 99.999% purity (5N-CeO 2 ) is about 1/100 of that with 99.9% purity (3N-CeO 2 ) as confirmed by the fluorescence intensity of impurities obtained by Raman spectroscopy. The Electronic Conductivity for the 5N-CeO 2 was measured at T = 973 K to 1173 K, and the results are essentially the same as those for the 3N-CeO 2 . The Electronic Conductivity increases with decreasing of P (O 2 ) following slope values of − 1/4 to − 1/6. The − 1/4 dependent region becomes narrower for the 5N-CeO 2 than that for the 3N-CeO 2 . For both types of ceria, the P (O 2 ) independent region appears in the same region of higher than 10 − 2 and 10 − 3 MPa at T = 1073 K and 973 K, respectively. Activation energies for the 5N-CeO 2 were 2.2 eV, 2.6 eV and 1.9 eV in P (O 2 ) dependent regions of − 1/6, − 1/4 and 0, respectively.
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Electronic Conductivity of CeO2: Its Dependence on Oxygen Partial Pressure and Temperature
Electrochemical and Solid-State Letters, 2010Co-Authors: Yueping Xiong, Haruo Kishimoto, Katsuhiko Yamaji, Masashi Yoshinaga, Teruhisa Horita, Manuel E. Brito, Harumi YokokawaAbstract:The Electronic Conductivity of pure ceria was successfully measured by a dc polarization technique based on the Hebb-Wagner ion blocking method at T = 873-1273 K. The Electronic Conductivity increased with increasing temperature at given P(O 2 ) values. It also increased with decreasing P(O 2 ) following slope values of -1/6 to -1/4. At 873-1073 K, no P(O 2 ) dependent region was observed at higher P(0 2 ) more than 10 -2 , 10 -4 , and 10 -5 MPa at 1073, 973, and 873 K, respectively. Activation energies calculated from the Arrhenius plots for those different regions were 2.2, 2.9, and 1.9 eV for P(O 2 ) dependences of -1/6, -1/4, and 0 regions, respectively.
Myriam Douin - One of the best experts on this subject based on the ideXlab platform.
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Improvement by heating of the Electronic Conductivity of cobalt spinel phases, electrochemically synthesized in various electrolytes
Journal of Solid State Chemistry, 2009Co-Authors: Myriam Douin, Lionel Goubault, Michel Menetrier, Emilie Bekaert, Patrick Bernard, Liliane Guerlou-demourgues, Claude DelmasAbstract:The nature of the alkaline electrolyte (based on KOH, NaOH, LiOH), in which Co3O4 spinel type phases are synthesized by electrooxidation of CoO, is shown to play a key role on the composition, the structure and the Electronic Conductivity of the materials. In the materials, prepared in pure LiOH electrolyte or in mixed ternary electrolyte (KOH, NaOH, LiOH), Co4+ ions are present in the octahedral framework, which entails Electronic delocalization in the cobalt T2g band and a high Conductivity. The structure of the sample, synthesized in KOH, is on the opposite closer to that of ideal Co3O4, with only Co3+ in the octahedral sublattice, which leads to a semi-conducting behavior. Whatever the initial material, a thermal treatment induces an increase of the Co4+/Co3+ ratio in the octahedral network, resulting in a significant increase of the Electronic Conductivity.
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Improvement by heating of the Electronic Conductivity of cobalt spinel phases, electrochemically synthesized in various electrolytes
Journal of Solid State Chemistry, 2009Co-Authors: Myriam Douin, Lionel Goubault, Michel Menetrier, Emilie Bekaert, Patrick Bernard, Liliane Guerlou-demourgues, Claude DelmasAbstract:The nature of the alkaline electrolyte (based on KOH, NaOH, LiOH), in which Co{sub 3}O{sub 4} spinel type phases are synthesized by electrooxidation of CoO, is shown to play a key role on the composition, the structure and the Electronic Conductivity of the materials. In the materials, prepared in pure LiOH electrolyte or in mixed ternary electrolyte (KOH, NaOH, LiOH), Co{sup 4+} ions are present in the octahedral framework, which entails Electronic delocalization in the cobalt T{sub 2g} band and a high Conductivity. The structure of the sample, synthesized in KOH, is on the opposite closer to that of ideal Co{sub 3}O{sub 4}, with only Co{sup 3+} in the octahedral sublattice, which leads to a semi-conducting behavior. Whatever the initial material, a thermal treatment induces an increase of the Co{sup 4+}/Co{sup 3+} ratio in the octahedral network, resulting in a significant increase of the Electronic Conductivity. - Graphical abstract: In 'Co{sub 3}O{sub 4}' type spinel phases synthesized by eleectrooxidation, the nature of the alkaline electrolyte allows to monitor the amounts of hydrogen and lithium, inserted in spinel framework and therefore the Electronic Conductivity. Whatever the initial synthesis electrolyte, a moderate thermal treatment of the materials induces a significant increase ofmore » the Electronic Conductivity, due to a structural reorganization (illustrated by the evolution of the cell parameter) and an increase of the Co{sup 4+}/Co{sup 3+} ratio in the octahedral framework.« less
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effect of thermal treatment on the Electronic Conductivity properties of cobalt spinel phases synthesized by electro oxidation in ternary alkaline electrolyte koh lioh naoh
Chemistry of Materials, 2008Co-Authors: Myriam Douin, Lionel Goubault, Liliane Guerloudemourgues, Michel Menetrier, Emilie Bekaert, Patrick Bernard, Claude DelmasAbstract:A thermal treatment of Co3O4 type spinel phases, synthesized by electrooxidation of CoO powder in a mixed alkaline electrolyte (KOH, LiOH, NaOH), is shown to have an important influence on the Electronic Conductivity properties of the materials. The initial spinel phase contains hydrogen, lithium, cobalt vacancies, and especially Co4+ ions within the structure, leading to an Electronic Conductivity significantly larger than that of stoichiometric Co3O4. The thermal treatment, followed by in situ X-ray diffraction, TGA-MS and Electronic Conductivity measurements, induces a water release, coupled with an increase of the Co/O atomic ratio and a structural reorganization. The resulting cationic redistribution within the spinel framework entails an increase of the Co4+ amount in the [Co2O4] network and therefore of the Electronic Conductivity (by 3 orders of magnitude).
Teruhisa Horita - One of the best experts on this subject based on the ideXlab platform.
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Electronic Conductivity and Efficiency of SOFC Electrolytes
ECS Transactions, 2019Co-Authors: Katsuhiko Yamaji, Yueping Xiong, Haruo Kishimoto, Teruhisa Horita, Manuel E. Brito, Harumi YokokawaAbstract:Relatively high Electronic Conductivity of SOFCs' electrolytes significantly decrease the energy conversion efficiency on power generation. This feature was confirmed especially for LSGMC and GDC electrolytes. The effect of electron Conductivity on the efficiency for GDC electrolyte was very sensitive to fuel utilization rate. The efficiency increases with fuel utilization rate because the oxygen partial pressure in the fuel increases with fuel utilization rate and the Electronic Conductivity decreased with increasing the oxygen partial pressure.
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Electronic Conductivity of Scandia-Stabilized Zirconia Doped with 1 mol% CeO2
ECS Transactions, 2012Co-Authors: Taro Shimonosono, Haruo Kishimoto, Katsuhiko Yamaji, Teruhisa Horita, Manuel E. Brito, Mina Nishi, Harumi YokokawaAbstract:Scandia-stabilized zirconia (ScSZ) has been extensively studied for the application to solid oxide fuel cells (SOFCs) because of its higher oxide ion Conductivity compared to conventional yttria-stabilized zirconia (YSZ). The Electronic Conductivity of ScSZ is significantly lower than the ionic Conductivity but is important to determine the performance of SOFC materials. In the case of nickel – stabilized zirconia cermet anode, when the scandiastabilized zirconia was used, the durability against methane fuel was enhanced [1]. The minor carriers like electron and proton in ionic conductor may affect the reaction mechanism at the cermet anode as proposed in literature [2]. ScSZ with 10 mol% Sc2O3 has the highest ionic Conductivity among different content of Sc2O3 at 1273 K [3] and is generally doped with 1 mol% CeO2 to suppress the transformation of cubic to rhombohedral phase [4]. Since the valence state of cerium ion varies from 4+ to 3+ with decreasing oxygen partial pressure (p(O2)), the concentration of electron carrier in ScSZ would be affected by doping with CeO2 if the electrons on the trivalent Ce ions behave as carrier (CeZr+1/2OO Ce’Zr+1/2VO+1/4O2). In our previous study on the Electronic Conductivity of [(CeO2)x(ZrO2)1x]0.8(YO1.5)0.2 solid solution [5], it was observed that the Electronic Conductivity of the solid solution with CeO2 content of x 0.1 was 4 – 5 order-of-magnitude larger than that of x = 0, and that the Electronic Conductivity of solid solution with CeO2 had unusual p(O2) dependency like the concentration product of trivalent and tetravalent Ce ions. In this study, the Electronic Conductivity of 10 mol% Sc2O3-stabilized ZrO2 doped with 1 mol% CeO2 (1Ce10ScSZ) was measured using a modified HebbWagner ion blocking cell reported elsewhere [6]. The contribution of 1 mol% CeO2 to the Electronic conduction of ScSZ was investigated by clarifying the p(O2) and temperature dependence of Electronic Conductivity of 1Ce10ScSZ. Figure 1 shows the Electronic Conductivity of 1Ce10ScSZ at 1173 – 1273 K in the p(O2) range of 10 – 10 MPa. At p(O2) > 10 MPa, the Electronic Conductivity at 1273 K was proportional to the 1/4 power of p(O2). The 1/4 power dependence was also observed at 1173 K in p(O2) > 10 MPa. Such 1/4 power dependence is usually explained by the p(O2) dependence of Electronic hole concentration which is derived from the hole formation reaction (1/2VO +1/4O2 h + 1/2OO). At p(O2) > 10 MPa, the Electronic Conductivity at 1273 K was proportional to the -1/4 power of p(O2), which is usually interpreted as the p(O2) dependence of electron concentration which is derived from the electron formation reaction (1/2OO e’ + 1/2 VO +1/4O2). The solid line in fig. 1 shows the fitting curve of measured Conductivity data with following equation, e = h[p(O2) / 0.1MPa] + e[p(O2) / 0.1MPa] (1) where h and e are constants. In the p(O2) range of 10 – 10 MPa, the p(O2) dependence of Electronic Conductivity at 1273 K deviated from the 1/4 and -1/4 power law expressed in eq. (1). The upper deviation of Electronic Conductivity from the 1/4 and -1/4 power law is attributed to the increase of electron concentration due to the reduction of doped CeO2. It is meaning that the electron on trivalent Ce ion behaves as electron carrier. Because of the limited amount of Ce dopant (1 mol%), the -1/4 power dependence due to the ZrO2 matrix appeared at lower p(O2) (< 10 MPa). To investigate the contribution of 1 mol% CeO2 to the Electronic conduction of ScSZ in detail, the Electronic Conductivity of 1Ce10ScSZ is measured at 1173 K in the lower p(O2) region.
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Electronic Conductivity of Ni-doped yttria-stabilized zirconia
Solid State Ionics, 2012Co-Authors: Taro Shimonosono, Haruo Kishimoto, Katsuhiko Yamaji, Teruhisa Horita, Manuel E. Brito, Harumi YokokawaAbstract:Abstract The Electronic Conductivity of (NiO) 0.01 [(Y 2 O 3 ) 0.08 (ZrO 2 ) 0.92 ] 0.99 was measured with a modified ion blocking method at 1273 K in the oxygen partial pressure ( p (O 2 )) range of 10 − 3 –10 − 17 MPa. At p (O 2 ) > 10 − 6 and − 14 MPa, the Electronic Conductivity was proportional to the 1/4 and − 1/4 power of p (O 2 ) due to hole and electron conduction, respectively. The electron Conductivity was obviously smaller for Ni-doped YSZ than for YSZ by a factor of 2.0 at p (O 2 ) range of 10 − 14 –10 − 17 MPa. The measured Electronic Conductivity of Ni-doped YSZ was used to calculate the oxygen potential distribution in the electrolyte under the ion blocking condition. The lower oxygen potential region in the electrolyte was in excellent agreement with the darkly colored region found in the Ni-doped YSZ electrolyte after the Electronic Conductivity measurements.
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Electronic Conductivity of pure ceria
Solid State Ionics, 2011Co-Authors: Yueping Xiong, Haruo Kishimoto, Katsuhiko Yamaji, Masashi Yoshinaga, Teruhisa Horita, Manuel E. Brito, Harumi YokokawaAbstract:Abstract The Electronic Conductivity of pure ceria with two different impurity levels is examined by dc polarization technique based on the Hebb–Wagner ion blocking method. The impurity level for the ceria with 99.999% purity (5N-CeO 2 ) is about 1/100 of that with 99.9% purity (3N-CeO 2 ) as confirmed by the fluorescence intensity of impurities obtained by Raman spectroscopy. The Electronic Conductivity for the 5N-CeO 2 was measured at T = 973 K to 1173 K, and the results are essentially the same as those for the 3N-CeO 2 . The Electronic Conductivity increases with decreasing of P (O 2 ) following slope values of − 1/4 to − 1/6. The − 1/4 dependent region becomes narrower for the 5N-CeO 2 than that for the 3N-CeO 2 . For both types of ceria, the P (O 2 ) independent region appears in the same region of higher than 10 − 2 and 10 − 3 MPa at T = 1073 K and 973 K, respectively. Activation energies for the 5N-CeO 2 were 2.2 eV, 2.6 eV and 1.9 eV in P (O 2 ) dependent regions of − 1/6, − 1/4 and 0, respectively.
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Electronic Conductivity of CeO2: Its Dependence on Oxygen Partial Pressure and Temperature
Electrochemical and Solid-State Letters, 2010Co-Authors: Yueping Xiong, Haruo Kishimoto, Katsuhiko Yamaji, Masashi Yoshinaga, Teruhisa Horita, Manuel E. Brito, Harumi YokokawaAbstract:The Electronic Conductivity of pure ceria was successfully measured by a dc polarization technique based on the Hebb-Wagner ion blocking method at T = 873-1273 K. The Electronic Conductivity increased with increasing temperature at given P(O 2 ) values. It also increased with decreasing P(O 2 ) following slope values of -1/6 to -1/4. At 873-1073 K, no P(O 2 ) dependent region was observed at higher P(0 2 ) more than 10 -2 , 10 -4 , and 10 -5 MPa at 1073, 973, and 873 K, respectively. Activation energies calculated from the Arrhenius plots for those different regions were 2.2, 2.9, and 1.9 eV for P(O 2 ) dependences of -1/6, -1/4, and 0 regions, respectively.
Jürgen Janek - One of the best experts on this subject based on the ideXlab platform.
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Ionic and Electronic Conductivity of nitrogen-doped YSZ single crystals
Solid State Ionics, 2009Co-Authors: Ilia Valov, V. Rührup, R. Klein, T.-c. Rödel, Alexandra Stork, Stefan Berendts, M. Dogan, Martin Lerch, H.-d. Wiemhöfer, Jürgen JanekAbstract:The ionic and Electronic charge transport was studied for single crystals of 9.5 mol% yttria-stabilized zirconia with additional nitrogen doping (YSZ:N) of up to 7.5 at.% (referred to the anion sublattice and formula unit Zr0.83Y0.17O1.91) as a function of temperature and nitrogen content. The total Conductivity being almost equivalent to the oxygen ion Conductivity has been measured by AC impedance spectroscopy under vacuum conditions in order to prevent re-oxidation and loss of nitrogen. The Electronic Conductivity has been determined by Hebb-Wagner polarization using ion-blocking Pt microelectrodes in N-2 atmosphere. The ionic Conductivity of YSZ:N decreases in the presence of nitrogen at intermediate temperatures up to 1000 degrees C. The mean activation energy of ionic conduction strongly increases with increasing nitrogen content, from 1.0 eV for nitrogen-free YSZ up to 1.9 eV for YSZ containing 7.3 at.% N. Compared to nitrogen-free YSZ, the Electronic Conductivity first decreases at nitrogen contents of 2.17 and 5.80 at.%, but then increases again for a sample with 7.53 at X At temperatures of 850 degrees C and above, the presence of the N3- dopant fixes the electrode potential and thus the oxygen partial pressure at the Pt electrode to very low values. This corresponds to a pinning of the Fermi level at a relatively high energy in the upper half of the band gap. At 7.53 at.% N and 950 degrees C, the oxygen partial pressure in YSZ:N corresponds to p(O2) = 3x10(-18) bar. At temperatures above 850 degrees C, even in the presence of a very small oxygen concentration in the surrounding gas phase, the nitrogen ion dopant becomes highly mobile and thus diffuses to the surface where it is oxidized to gaseous N-2. The results are discussed in terms of the ionic and Electronic defect structures and the defect mobilities in YSZ:N. (C) 2009 Elsevier B.V. All rights reserved
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Ionic and Electronic Conductivity of nitrogen-doped YSZ single crystals
Solid State Ionics, 2009Co-Authors: Ilia Valov, Hans-dieter Wiemhöfer, V. Rührup, R. Klein, T.-c. Rödel, Alexandra Stork, Stefan Berendts, M. Dogan, Martin Lerch, Jürgen JanekAbstract:Abstract The ionic and Electronic charge transport was studied for single crystals of 9.5 mol% yttria-stabilized zirconia with additional nitrogen doping (YSZ:N) of up to 7.5 at.% (referred to the anion sublattice and formula unit Zr0.83Y0.17O1.91) as a function of temperature and nitrogen content. The total Conductivity being almost equivalent to the oxygen ion Conductivity has been measured by AC impedance spectroscopy under vacuum conditions in order to prevent re-oxidation and loss of nitrogen. The Electronic Conductivity has been determined by Hebb–Wagner polarization using ion-blocking Pt microelectrodes in N2 atmosphere. The ionic Conductivity of YSZ:N decreases in the presence of nitrogen at intermediate temperatures up to 1000 °C. The mean activation energy of ionic conduction strongly increases with increasing nitrogen content, from 1.0 eV for nitrogen-free YSZ up to 1.9 eV for YSZ containing 7.3 at.% N. Compared to nitrogen-free YSZ, the Electronic Conductivity first decreases at nitrogen contents of 2.17 and 5.80 at.%, but then increases again for a sample with 7.53 at.%. At temperatures of 850 °C and above, the presence of the N3− dopant fixes the electrode potential and thus the oxygen partial pressure at the Pt electrode to very low values. This corresponds to a pinning of the Fermi level at a relatively high energy in the upper half of the band gap. At 7.53 at.% N and 950 °C, the oxygen partial pressure in YSZ:N corresponds to pO2 = 3 × 10− 18 bar. At temperatures above 850 °C, even in the presence of a very small oxygen concentration in the surrounding gas phase, the nitrogen ion dopant becomes highly mobile and thus diffuses to the surface where it is oxidized to gaseous N2. The results are discussed in terms of the ionic and Electronic defect structures and the defect mobilities in YSZ:N.