Phase diagram of the ZrO2–Gd2O3–Al2O3 system

Lakiza, S. M.; Fabrichnaya, Olga; Ch, Wang; Zinkevich, M.; Aldinger, Fritz

doi:10.1016/j.jeurceramsoc.2004.11.011

Cited by 90 publications

(66 citation statements)

References 30 publications

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“…For our cathode, an equivalent lanthanide zirconate pyrochlore could be expected, i.e., Gd 2 Zr 2 O 7 . Although the pyrochlore structure is stable in the Gd-Zr-O system for our range of temperatures [24], other work has not shown the formation of the gadolinium zirconate pyrochlore, e.g., Takeda et al [25] do not observe it between 8YSZ and Gd 0.8 Sr 0.2 MnO 3−δ at 1000-1400 • C. Actually, the gadolinium zirconate pyrochlore has the narrowest region of existence among the lanthanide zirconate pyrochlores. The enthalpy of formation of Ln 2 Zr 2 0 7 (Ln = Lanthanides) decreases with decreasing ionic radius of the rare earth cation [26] and therefore, the stability of the pyrochlore is reduced in the order La 2 [27].…”

Section: Electrochemical and Cell Performancementioning

confidence: 58%

GdBaCo2O5+x layered perovskite as an intermediate temperature solid oxide fuel cell cathode

Tarancón¹,

Morata²,

Dezanneau³

et al. 2007

Journal of Power Sources

134

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GdBaCo 2 O 5+x (GBCO) was evaluated as a cathode for intermediate-temperature solid oxide fuel cells. A porous layer of GBCO was deposited on an anode-supported fuel cell consisting of a 15 m thick electrolyte of yttria-stabilized zirconia (YSZ) prepared by dense screen-printing and a Ni-YSZ cermet as an anode (Ni-YSZ/YSZ/GBCO). Values of power density of 150 mW cm −2 at 700 • C and ca. 250 mW cm −2 at 800 • C are reported for this standard configuration using 5% of H 2 in nitrogen as fuel. An intermediate porous layer of YSZ was introduced between the electrolyte and the cathode improving the performance of the cell. Values for power density of 300 mW cm −2 at 700 • C and ca. 500 mW cm −2 at 800• C in this configuration were achieved.

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Section: Electrochemical and Cell Performancementioning

confidence: 58%

GdBaCo2O5+x layered perovskite as an intermediate temperature solid oxide fuel cell cathode

Tarancón¹,

Morata²,

Dezanneau³

et al. 2007

Journal of Power Sources

134

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“…[23,[26][27][28][29][30][31][32][33] The calculated data for invariant reactions (temperature and phase compositions) are compared in Table 2 with experimental data. [26][27][28]34,35] The difference with the previous assessment of Lakiza et al [15] is that the F + Pyr two-phase field is narrower and there is no eutectoid reaction F = M + Pyr which was obtained at lower temperatures in the calculations. [15] However, experiments can not distinguish between the single phase pyrochlore and the F + Pyr two-phase field and there is still discussion in the literature if the transformation of Fluorite to Pyrochlore is of the first or second order.…”

Section: Binary Systemsmentioning

confidence: 88%

“…The ZrO 2 -Gd 2 O 3 and Gd 2 O 3 -Al 2 O 3 thermodynamic descriptions were derived by Lakiza et al [15] based on phase equilibrium data and calorimetric measurements. Due to changes in the thermodynamic functions of the ZrO 2 and Gd 2 O 3 phases, the parameters of both binary systems were re-assessed in the present study.…”

Section: Binary Systemsmentioning

confidence: 99%

“…Since the time of publication, new data on the thermodynamics of transformations in the ZrO 2 , [11] Gd 2 O 3 and Y 2 O 3 [12] have been published. Additionally new heat capacity measurements for the GdAlO 3 , Gd 4 Al 2 O 9 and Gd 3 Al 5 O 12 phases have been performed by Chaudhury et al [13] and of the Gd 2 Zr 2 O 7 , pyrochlore by Liu et al [14] In the previous work of Lakiza et al, [15] the heat capacities of the Gd 4 Al 2 O 9 and Gd 3 Al 5 O 12 phases were described according to the Neumann-Kopp rule and therefore new data should be included into the database. The heat capacity of the Gd 2 Zr 2 O 7 and GdAlO 3 phases used in work of Lakiza et al [15] needs to be compared with more recent data.…”

Section: Introductionmentioning

confidence: 99%

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Up-Date of a Thermodynamic Database of the ZrO2-Gd2O3-Y2O3-Al2O3 System for TBC Applications

Fabrichnaya

Seifert

2010

J. Phase Equilib. Diffus.

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The thermodynamic database of the ZrO 2 -Gd 2 O 3 -Y 2 O 3 -Al 2 O 3 system is up-dated taking into account new data on lattice stabilities of ZrO 2 , Gd 2 O 3 and Y 2 O 3 and heat capacity measurements for the monoclinic phase Gd 4 Al 2 O 9 and phase with garnet structure Gd 3 Al 5 O 12 . New data for the heat capacities of Gd 2 Zr 2 O 7 (pyrochlore) and GdAlO 3 (perovskite) as well as on the enthalpy of formation of fluorite solid solutions (Zr 12x Gd x )O 22x/2 were found to be in good agreement with calculated results. In comparison with the previous assessment, taking into account new experimental data resulted in a change of the melting character of the Gd 4 Al 2 O 9 phase from a peritectic one to a congruent one in the Gd 2 O 3 -Al 2 O 3 system. Correspondently, in the ternary system ZrO 2 -Gd 2 O 3 -Al 2 O 3 , the melting character of the three-phase assemblage Gd 2 O 3 (B), Gd 4 Al 2 O 9 and GdAlO 3 changed from eutectic to transition type U. The T 0 -lines for T/M and F/T diffusionless transformations and driving force of partitioning to equilibrium assemblage T + F were calculated in the ZrO 2 -Gd 2 O 3 -Y 2 O 3 system.

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“…One of the promising leading candidates for advanced TBC materials is the Yb-Gd-Y-stabilized zirconia (hereinafter YGYZ). The YGYZ coating has better oxidation resistance, improved sintering resistance, higher calcium-magnesium-alumino-silicate (CMAS) resistance, excellent phase stability, and lower thermal conductivity than YSZ coating; it has thermal conductivity of 0.80-1.24 W•(m•K) -1 for bulk YGYZ and of 2.1 W•(m•K) -1 for bulk 8YSZ [16][17][18][19]. The principal drawback of YGYZ coating is its low coefficient of thermal expansion (CTE), which does 4 not match the bond coat with a relatively large CTE; CTE is 9-1010 -6 •K -1 for bulk YGYZ, 10.5-11.510 -6 •K -1 for bulk 8YSZ, and 15.010 -6 •K -1 at 1000 o C for Ni-based bond coat [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Thermal durability and fracture behavior of layered Yb-Gd-Y-based thermal barrier coatings in thermal cyclic exposure

Jung

et al. 2017

Surface and Coatings Technology

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The effects of structural design on the thermal durability of Yb-Gd-Y-based thermal barrier coatings (TBCs) were investigated through thermal cyclic exposure tests, such as furnace cyclic thermal fatigue (FCTF) and jet engine thermal shock (JETS) tests. The effects of composition in the bond coat and feedstock purity for the buffer layer on its lifetime performance were also examined. To overcome the drawbacks of Yb-Gd-Y material with poor thermal durability due to poor mechanical properties and low coefficient of thermal expansion, a buffer layer was introduced in the Yb-Gd-Y-based TBC systems. In the FCTF tests, the TBC with the CoNi-based bond coat and the buffer layer of regular purity showed a longer lifetime performance than other TBCs, especially the TBCs without the buffer layer.In the JETS tests, the TBC with the Ni-based bond coat and the buffer layer of high purity showed a sound condition after 2000 cycles, showing better interfacial stability for TBC with the Ni-based bond coat rather than that with the CoNi-based bond coat in the single layer coatings without the buffer layer. The buffer layer effectively enhanced the thermal durability in slow temperature change, while the bond-coat composition and the feedstock purity for the buffer layer were found to be important factor to improve the thermal durability of the TBC in fast temperature change. Finally, these research findings allow us to control the structure, composition, and feedstock purity in TBC system for improving the thermal durability in cyclic thermal environments.

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Phase diagram of the ZrO2–Gd2O3–Al2O3 system

Cited by 90 publications

References 30 publications

GdBaCo2O5+x layered perovskite as an intermediate temperature solid oxide fuel cell cathode

GdBaCo2O5+x layered perovskite as an intermediate temperature solid oxide fuel cell cathode

Up-Date of a Thermodynamic Database of the ZrO2-Gd2O3-Y2O3-Al2O3 System for TBC Applications

Thermal durability and fracture behavior of layered Yb-Gd-Y-based thermal barrier coatings in thermal cyclic exposure

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