Phase Stability of<i>t</i>′‐Zirconia‐Based Thermal Barrier Coatings: Mechanistic Insights

Krogstad, Jessica A.; Krämer, Stephan; Lipkin, Don M.; Johnson, Curtis A.; Mitchell, David R. G.; Cairney, Julie M.; Levi, Carlos G.

doi:10.1111/j.1551-2916.2011.04531.x

Cited by 132 publications

(99 citation statements)

References 50 publications

(67 reference statements)

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“…from tetragonal to monoclinic, initiated by a temperature driven diffusion of yttrium, occurs at temperatures above 1100 °C [22][23][24]. Besides the significantly lower temperatures of the experiments described herein, both processes would affect the whole top-coat instead of creating a partially densified ceramic, as shown in Figure 7C.…”

Section: Lab-scale Experimentsmentioning

confidence: 92%

“…Since no zirconium was added for the experiments described herein, it implies a partial solution of the zirconia within the top-coat to provide the zirconium for the recrystallization process. Another option is a densification mechanism by grain growth via sintering in combination with a partial phase transformation from tetragonal to monoclinic zirconia (going along with a volume increase of~4%): In general, a significant grain growth via sintering of YSZ ceramics as well as a phase transformation from tetragonal to monoclinic, initiated by a temperature driven diffusion of yttrium, occurs at temperatures above 1100 • C [22][23][24]. Besides the significantly lower temperatures of the experiments described herein, both processes would affect the whole top-coat instead of creating a partially densified ceramic, as shown in Figure 7C.…”

Section: Lab-scale Experimentsmentioning

confidence: 99%

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High Temperature Corrosion Studies of a Zirconia Coating: Implications for Waste-to-Energy (WTE) Plants

et al. 2016

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Abstract:Corrosion of functional parts within waste-to-energy (WTE) plants significantly reduces their efficiency with respect to maintenance costs. Currently, nickel-based alloy claddings, several millimeters thick, are the state of the art as anti-corrosion coating. Another approach is to utilize thermally sprayed multilayer coatings with a zirconia top-coat. Lab-scale experiments under simulated WTE plant conditions and in situ tests within a WTE plant revealed a partially reduced porosity of the zirconia top-coat after the experiments, enabling the coating to act as a barrier against aggressive gases. In a lab-scale experiment sample the pores are filled up with zirconia, while the pores of the in situ samples are filled up with newly formed metal (Cr, Ni, Fe) oxides.

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Section: Lab-scale Experimentsmentioning

confidence: 92%

Section: Lab-scale Experimentsmentioning

confidence: 99%

High Temperature Corrosion Studies of a Zirconia Coating: Implications for Waste-to-Energy (WTE) Plants

et al. 2016

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“…The remarkable durability of 8YSZ is ascribed to its superior toughness [2] based on a ferroelastic domain switching mechanism [1,3]. However, 8YSZ is metastable as a single tetragonal phase and eventually decomposes into Y-rich cubic and Y-lean tetragonal domains, the latter susceptible to the disruptive monoclinic transformation [4]. Accordingly, important goals in the development of advanced TBCs are phase stability at the higher temperatures (>1400 K) and improved toughness to mitigate a host of potential damage mechanisms [1].…”

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confidence: 99%

Ferroelastic switching of doped zirconia: Modeling and understanding from first principles

et al. 2014

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The properties of materials at high temperatures are often determined by complex thermodynamic mechanisms. One of the most prominent examples is the stabilization of tetragonal and cubic zirconia, which we investigate using density functional theory. The results show that the minimum energy path for the tetragonal-to-cubic phase transformation differs significantly from the paths discussed in the literature so far. This provides insight into the properties of compositions codoped with yttria and titania, an approach that has recently been proposed for the design of thermal barrier coatings. Zirconia-based materials offer many appealing properties, including a low thermal conductivity and a high ionic conductivity, as well as the potential for remarkable toughness. Hence, they are employed in a wide variety of applications, e.g., as catalyst supports, ionic conductors in sensors and solid oxide fuel cells, and thermal barrier coatings (TBC) for gas turbines in propulsion and power generation. In the latter case, a 150-1000 μm thick zirconia-based coating is applied to the turbine's superalloy components to protect them from the extreme temperatures generated during combustion. This improves the durability of the components and also enables an increase of the operation temperature and fuel efficiency [1].Pure ZrO 2 is not suitable for most applications because of the monoclinic-tetragonal phase transition at approximately 1500 K, which involves a disruptive volume change (∼4%) that degrades its mechanical integrity [1]. Thus, most ZrO 2 materials are doped to control or suppress the transformation, as it is the case for state-of-the-art TBCs based on singlephase tetragonal zirconia stabilized with 8 ± 1 mol % YO 1.5 (8YSZ). The remarkable durability of 8YSZ is ascribed to its superior toughness [2] based on a ferroelastic domain switching mechanism [1,3]. However, 8YSZ is metastable as a single tetragonal phase and eventually decomposes into Y-rich cubic and Y-lean tetragonal domains, the latter susceptible to the disruptive monoclinic transformation [4]. Accordingly, important goals in the development of advanced TBCs are phase stability at the higher temperatures (>1400 K) and improved toughness to mitigate a host of potential damage mechanisms [1]. For this purpose, it is essential to understand the fundamental origins of the mechanisms underlying the stabilization and toughening of the tetragonal phase.A common approach to stabilize the higher temperature forms of ZrO 2 involves doping with trivalent cations, most commonly Y 3+ , with the concomitant introduction of charged oxygen vacancies (F 2+ ) [5,6]. For TBCs, the useful composi-* carbogno@fhi-berlin.mpg.de Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.tional range is very narrow (8 ± 1 mol % YO 1.5 ): Underdoping renders the structure transformable to monocl...

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“…[85][86][87] The transformation of the t¢ phase has been shown to occur by the formation of a two-phase lamellar microstructure with high-yttria-content and low-yttria-content phases, which then transform to the monoclinic phase. [88] The t¢ phase can be stabilized using dopants such as magnesium, [89] ytterbium, [90] and gadolinium. [41] The decomposition of the t¢ phase at high temperatures limits the maximum operating temperature of the coating.…”

Section: Stabilitymentioning

confidence: 99%

Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

Fergus

2014

Metallurgical and Materials Transactions E

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One of the important applications of yttria-stabilized zirconia (YSZ) is as a thermal barrier coating for gas turbine engines. While YSZ performs well in this function, the need for increased operating temperatures to achieve higher energy conversion efficiencies, requires the development of improved materials. To meet this challenge, some rare-earth zirconates that form the cubic fluorite-derived pyrochlore structure are being developed for use in thermal barrier coatings due to their low thermal conductivity, excellent chemical stability, and other suitable properties. In this paper, the thermal conductivities of current and prospective oxides for use in thermal barrier coatings are reviewed. The factors affecting the variations and differences in the thermal conductivities and the degradation behaviors of these materials are discussed.

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Phase Stability oft′‐Zirconia‐Based Thermal Barrier Coatings: Mechanistic Insights

Cited by 132 publications

References 50 publications

High Temperature Corrosion Studies of a Zirconia Coating: Implications for Waste-to-Energy (WTE) Plants

High Temperature Corrosion Studies of a Zirconia Coating: Implications for Waste-to-Energy (WTE) Plants

Ferroelastic switching of doped zirconia: Modeling and understanding from first principles

Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

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