Effect of Water Vapor on Mass Transfer in Polycrystalline Yb2Si2O7 under Oxygen Potential Gradients at High Temperatures

Steam oxidation and microstructural evolution of rare earth silicate environmental barrier coatings

“…This behavior was not observed for (Y/Yb)DS exposed to dry air under the same conditions, where the (Y/Yb)MS and porosity concentrations remained at 7% ± 2% and 6% ± 3% area fraction, respectively, for all exposures up to 500 h 20 . Rare earth cation transport to the gas–EBC interface has been shown to be prevalent for YbDS and YbMS exposed to steam, while oxidant transport occurs in the opposite direction toward the interface 23–25 . As such, diffusion of Y and Yb cations to the gas–EBC interface may preferentially occur with the (Y/Yb)MS minor phase over the (Y/Yb)DS primary phase, resulting in decreased (Y/Yb)MS content within the coating through the formation of porosity and additional (Y/Yb)DS.…”

Oxygen K-edge spectra of Yb2O 3 polymorphs, Yb2SiO5, and Yb2Si2O7: First-principles simulations and EELS measurements

“…Hence, evaluating the interdiffusion of cations and anions along GBs in a wafer allows us to accurately characterize the diffusion properties. This measurement has been extended to an environment containing water vapor [24,25]. Atomic diffusivity from oxygen permeation and tracer diffusion experiments [22,23,26] could be used for the estimation of oxidation rates of an underlying bonding layer [27].…”

“…These analyses are expected to be useful also in the case of water vapor corrosion. For example, within the interior region of a Yb 2 Si 2 O 7 wafer, the number of Yb 2 SiO 5 particles increases and the size of these particles enlarges during water vapor exposure under oxygen potential gradients at 1673 K [25]. This reaction is not caused by the decomposition of Yb 2 Si 2 O 7 to Yb 2 SiO 5 and SiO 2 but should relate to the creation and diffusion of cations and anions at around GBs.…”

“…The existence of similar states in the Yb silicates has been confirmed in the valence EELS spectra as a weak terrace[51]. Moreover, a marginal amount of Yb 2+ ions could coexist in rare-earth compounds, as confirmed by X-ray photoemission spectroscopy for Yb 2 Si 2 O 7[25,52], which can also affect the O K-edge spectra. Although weak contributions possibly exist from the above factors, as already discussed for the spectral comparison of cubic Yb 2 O 3 , based on our results, the 4f orbitals and Yb 2+ ions may have a negligible effect on the O K-edge spectra in Yb compounds.…”

Design of a new yttrium silicate Environmental Barrier Coating (EBC) based on the relationship between microstructure, transport properties and protection efficiency

“…It has been shown that oxygen permeation proceeded via mutual diffusion of oxide and Yb ions at the grain boundaries with a large contribution from oxide ions. with the introduction of H 2 O to O 2 , the interdiffusion of oxide and Yb ions was accelerated, but no oxygen permeation was detected [40,72]. YbDS is known to have a different crystalline structure [29] and consequently may possess properties of mass transfer, as different oxygen lattice and grain boundary diffusion coefficient.…”