Phase diagram calculations of ZrO2-based ceramics with an emphasis on the reduction/oxidation equilibria of cerium ions in the ZrO2-YO1.5-CeO2-CeO1.5 system

Yokokawa, Harumi; Sakai, Natsuko; Horita, Teruhisa; Yamaji, Katsuhiko; Xiong, Yueping; Otake, Takanori; Yugami, Hiroo; Kawada, Tatsuya; Mizusaki, Junichiro

doi:10.1361/105497101770338842

Cited by 30 publications

(17 citation statements)

References 27 publications

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“…The thermodynamic properties of rare earth doped ceria [23] as well as zirconia systems [35] were obtained by phase diagram calculations; interaction parameters for the ceria-based fluorite oxides were determined so as to reproduce the oxygen nonstoichiometry in pure ceria and doped ceria with the aid of the results from theoretical calculations [36,37]. These data were used to make attempts to correlate the electronic and proton behaviors with the thermodynamic activity of dopants and hosts [38].…”

Section: Thermodynamic Datamentioning

confidence: 99%

“…Interdiffusion between YSZ and rare earth doped ceria is important, because the oxideion conductivity decreases significantly in the middle of the concentration range [22]. Thermodynamic [23] and interdiffusion [24] properties between YSZ and doped ceria are well investigated. When the three layers of cathode/doped ceria/YSZ are fabricated, the diffusion of Sr through the rare earth doped ceria from the cathode to YSZ becomes one of the key issues, because the strontium zirconate formation may take place at the ceria/YSZ interfaces not only during the fabrication but also during operation.…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamic and kinetic considerations on degradations in solid oxide fuel cell cathodes

Yokokawa

Sakai

Horita

et al. 2008

Journal of Alloys and Compounds

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152

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Section: Thermodynamic Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermodynamic and kinetic considerations on degradations in solid oxide fuel cell cathodes

Yokokawa

Sakai

Horita

et al. 2008

Journal of Alloys and Compounds

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152

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“…To satisfy this condition, the proper concentration of CeO 1.5 was determined so as to provide this oxygen potential from the CeO 1.5 /CeO 2 equilibrium. In a similar manner to the derivation of concentration of CeO 1.5 or YO 2 , the enthalpy term for electron/hole formation can be given as follows 10,11 These values are also listed in Table II. The calculated CeO 2 concentration dependence of the CeO 1.5 formation enthalpy term is essentially the same as those experimental values as shown in Fig.…”

Section: ͓5͔mentioning

confidence: 99%

“…However, this effect is confirmed to be negligible in the analysis on the thermogravimetric results of rare earth doped ceria. 6,11 Another possible reason for this deviation is the increase in the CeO 1.5 concentration and corresponding decrease in the CeO 2 concentration. A similar effect should appear in the CeO 2 dependence of electron conductivity across the solid solution, since the CeO 2 concentration decreases in a similar manner.…”

Section: ͓5͔mentioning

confidence: 99%

Electronic Conductivity of ZrO[sub 2]–CeO[sub 2]–YO[sub 1.5] Solid Solutions in a Wide Range of Temperature and Oxygen Partial Pressure

Xiong

Yamaji

Sakai

et al. 2006

J. Electrochem. Soc.

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The electron and hole conductivity of ͓͑ZrO 2 ͒ 1−x ͑CeO 2 ͒ x ͔ 0.8 ͑YO 1.5 ͒ 0.2 ͑x = 0-1,0.1 step͒ solid solutions was measured by dc polarization method using a modified Hebb-Wagner's ion blocking cell at 973, 1073, 1173, and 1273 K as a function of oxygen partial pressure. All measured data were fitted to the sum of the electron conductivity having a p O 2 −1/4 dependence and the hole conductivity having a p O 2 1/4 dependence. At all temperatures, with increasing CeO 2 concentration, the electron conductivity drastically increased at x = 0-0.4 and slightly decreased at x = 0.6-1.0, leading to a maximum at x = 0.4-0.5. The logarithmic hole conductivity linearly increased with CeO 2 concentration for x = 0-1.ZrO 2 -CeO 2 -YO 1.5 ͑ZCY͒ solid solutions have higher oxygen surface exchange coefficients than ZrO 2 -YO 1.5 ͑YSZ͒ and CeO 2 -YO 1.5 ͑YDC͒ electrolytes. 1 This superior surface catalytic activity of ZCY solid solutions should be related to the mixed electronic/ionic conduction, and therefore, the electronic conductivity of ZCY solid solutions has been extensively investigated in our group by a dc polarization method with a Hebb-Wagner's type ionblocking cell. 2,3 In our previous study, 2 the electronic conductivity of ͓͑ZrO 2 ͒ 1−x ͑CeO 2 ͒ x ͔ 0.8 ͑YO 1.5 ͒ 0.2 ͑ZCY, x = 0-1.0, 0.1 step͒ solid solutions at 1273 K in a oxygen partial pressure, p O 2 , region of log͕p O 2 /MPa͖ Ϲ −3 is directly measured by the dc-polarization method with a Hebb-Wagner's ion blocking cell 4,5 as a function of p O 2 . It was revealed that the main charge carrier is electron for ZYCs with CeO 2 containing compositions ͑x = 0.3-0.7͒ at log͕p O 2 /MPa͖ = −6 to −3. However, the slope for x = 0.1, x = 0.9, and x = 1.0 was found to deviate from −1/4 toward the higher oxygen partial pressure region of log͕p O 2 /MPa͖ = −4 to −3 at 1273 K. For similar materials of 20 mol % rare earth oxide ͑REO 1.5 ͒ doped CeO 2 ͑Ce 0.8 RE 0.2 O 1.9 ,rare earth͑RE͒ = Yb,Y,Gd, Sm, Nd, La͒ electrolytes, the hole conduction was also observed in the higher oxygen partial pressure region of ͑log͕p ͑O 2 ͒ /MPa͖ Յ −1͒ at lower temperatures ͑973, 1073, 1173, and 1273 K͒. 3,6,7 In this study, further investigation on electronic conductivity of ͓͑ZrO 2 ͒ 1−x ͑CeO 2 ͒ x ͔ 0.8 ͑YO 1.5 ͒ 0.2 ͑ZCY,x = 0-1, 0.1 step͒ solid solutions were carried out in the higher p O 2 region of log͕p O 2 /MPa͖ = −3 to −1 at lower temperatures of 973, 1073, and 1173 K. The electronic conductivity of ZCY solid solutions was directly measured with a modified Hebb-Wagner's ion blocking cell. ExperimentalSamples.-͓͑ZrO 2 ͒ 1−x ͑CeO 2 ͒ x ͔ 0.8 ͑YO 1.5 ͒ 0.2 ͑ZCY, x = 0-1.0, 0.1 step͒ solid solutions were prepared by solid-state reactions among ZrO 2 , CeO 2 , and Y 2 O 3 powders. ZrO 2 ͑Tosoh TZ-0͒, CeO 2 ͑Wako Pure Chemical Industries, Ltd., 99.9%͒ and Y 2 O 3 ͑Wako Pure Chemical Industries, Ltd., 99.9%͒ powders were mixed for 24 h by ballmilling with ethanol as a solvent. The mixed powders were dried at 323-373 K for 24 h and compacted into disks of 25 mm diam and 3-5 mm thickne...

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“…Ion sputtering rates, and by association ion damage, tends to correlate with atomic number, melting point, hardness, density and crystal structure (Giannuzzi, 2005). STN and YSZ show differences in hardness (STN ∼25% < YSZ) and melting point (STN ∼27% < YSZ) (Leshchenko et al, 1982;Yokokawa et al, 2001) which may account for the effect of ion damage on pattern quality. The two materials also show a difference in density (STN ∼15% < Fig.…”

Section: Effect Of Fib Currentmentioning

confidence: 99%

Effects of focused ion beam milling on electron backscatter diffraction patterns in strontium titanate and stabilized zirconia

Saowadee

Agersted

Bowen

2012

Journal of Microscopy

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SummaryThis study investigates the effect of focused ion beam (FIB) current and accelerating voltage on electron backscatter diffraction pattern quality of yttria-stabilized zirconia (YSZ) and Nb-doped strontium titanate (STN) to optimize data quality and acquisition time for 3D-EBSD experiments by FIB serial sectioning. Band contrast and band slope were used to describe the pattern quality. The FIB probe currents investigated ranged from 100 to 5000 pA and the accelerating voltage was either 30 or 5 kV. The results show that 30 kV FIB milling induced a significant reduction of the pattern quality of STN samples compared to a mechanically polished surface but yielded a high pattern quality on YSZ. The difference between STN and YSZ pattern quality is thought to be caused by difference in the degree of ion damage as their backscatter coefficients and ion penetration depths are virtually identical. Reducing the FIB probe current from 5000to 100 pA improved the pattern quality by 20% for STN but only showed a marginal improvement for YSZ. On STN, a conductive coating can help to improve the pattern quality and 5 kV polishing can lead to a 100% improvement of the pattern quality relatively to 30 kV FIB milling. For 3D-EBSD experiments of a material such as STN, it is recommended to combine a high kV FIB milling and low kV polishing for each slice in order to optimize the data quality and acquisition time.

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Phase diagram calculations of ZrO2-based ceramics with an emphasis on the reduction/oxidation equilibria of cerium ions in the ZrO2-YO1.5-CeO2-CeO1.5 system

Cited by 30 publications

References 27 publications

Thermodynamic and kinetic considerations on degradations in solid oxide fuel cell cathodes

Thermodynamic and kinetic considerations on degradations in solid oxide fuel cell cathodes

Electronic Conductivity of ZrO[sub 2]–CeO[sub 2]–YO[sub 1.5] Solid Solutions in a Wide Range of Temperature and Oxygen Partial Pressure

Effects of focused ion beam milling on electron backscatter diffraction patterns in strontium titanate and stabilized zirconia

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