Phase Evolution upon Aging of Air Plasma Sprayed t′‐Zirconia Coatings: <scp>II</scp>–Microstructure Evolution

Krogstad, Jessica A.; Leckie, Rafael M.; Krämer, Stephan; Cairney, Julie M.; Lipkin, Don M.; Johnson, Curtis A.; Levi, Carlos G.

doi:10.1111/j.1551-2916.2012.05460.x

Cited by 74 publications

(45 citation statements)

References 31 publications

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“…Simultaneous presence of two tetragonal phases along with cubic precipitates in YSZ, observed by room temperature XRD, in initially t zirconia has been reported in the literature. 25,26 Recent understanding of the precipitation of cubic phase in YSZ indicates that the tetragonal phase with large tetragonality is an artifact of the tetragonal phase being strained in the vicinity of the cubic precipitates due to coherency. 8 The present results are consistent with this hypothesis.…”

Section: Annealing Time (H)mentioning

confidence: 99%

Phase and fracture toughness evolution during isothermal annealing of spark plasma sintered zirconia co-doped with Yb, Gd and Nd oxides

Ponnuchamy

Gandhi

2015

Journal of the European Ceramic Society

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Section: Annealing Time (H)mentioning

confidence: 99%

Phase and fracture toughness evolution during isothermal annealing of spark plasma sintered zirconia co-doped with Yb, Gd and Nd oxides

Ponnuchamy

Gandhi

2015

Journal of the European Ceramic Society

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“…In thermodynamic average, this ferroelastic switching dynamics leads to an apparent cubic Fm3m structure that is, however, never realized as a stable or metastable structure in pure ZrO 2 . Recent advancements in pulsed, high-intensity electron and light sources [24,25] should enable an experimental examination of our findings (and of the computed barriers), given that the tetragonal displacements of the anions can be detected by vibrational spectroscopy [26] or electron diffraction [27]. Similar mechanisms may also be active in other materials, given that soft vibrational modes and tetragonal-cubic phase transitions are not a unique feature of zirconia.…”

mentioning

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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“…40 Yttria segregation to both external surfaces and grain boundaries has been observed for YSZ containing an Y 2 O 3 level varying from 2 to 19 mol %. [41][42][43][44][45] As revealed from our STEM observation shown above, significant local enrichment of Y atoms can also occur within YSZ grains, where the concentration of Y in the L10 cation ordered regions (Zr 2 Y 2 O 7 ) increases to 50 mole % from the initial doping level of 3.7 mol % Y 2 O 3 . The nucleation and growth of Y-enriched regions in the grain can deplete Y in the surrounding area.…”

Section: Experimental and Computation Methodsmentioning

confidence: 61%

Oxygen vacancy ordering induced displacements of cations in yttria-stabilized zirconia

Wang

Cai

et al. 2016

AIP Advances

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Using scanning transmission electron microscopy, we report direct observation of oxygen vacancy ordering induced atomic displacements of the cation sub-lattice in yttria-stabilized zirconia (YSZ). We find that the cation lattice adopts a zigzag configuration along the [100] direction with alternately narrow and wide lattice spacings equivalent of 0.85 and 1.15 times of the (200) inter-planar distance of the cubic YSZ. Using atomistic simulations, we show that the cation displacements are induced by the alternate presence of oxygen vacancies at the (1/4, 1/4, 1/4) and (1/4, 3/4, 1/4) sites of the unit cells in the [001] direction. The results demonstrate that significant enrichment of yttrium atoms can occur within individual YSZ grains in addition to the typical surface or grain boundary segregation of dopant atoms.

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Phase Evolution upon Aging of Air Plasma Sprayed t′‐Zirconia Coatings: II–Microstructure Evolution

Cited by 74 publications

References 31 publications

Phase and fracture toughness evolution during isothermal annealing of spark plasma sintered zirconia co-doped with Yb, Gd and Nd oxides

Phase and fracture toughness evolution during isothermal annealing of spark plasma sintered zirconia co-doped with Yb, Gd and Nd oxides

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

Oxygen vacancy ordering induced displacements of cations in yttria-stabilized zirconia

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