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Atomic scale verification of oxide-ion vacancy distribution near a single grain boundary in YSZ.

An J, Park JS, Koh AL, Lee HB, Jung HJ, Schoonman J, Sinclair R, Gür TM, Prinz FB - Sci Rep (2013)

Bottom Line: We show significant oxygen deficiency due to segregation of oxide-ion vacancies near the grain-boundary core with half-width < 0.6 nm.Oxide-ion density distribution near a grain boundary simulated by molecular dynamics corroborated well with experimental results.Such column-by-column quantification of defect concentration in functional materials can provide new insights that may lead to engineered grain boundaries designed for specific functionalities.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA [2].

ABSTRACT
This study presents atomic scale characterization of grain boundary defect structure in a functional oxide with implications for a wide range of electrochemical and electronic behavior. Indeed, grain boundary engineering can alter transport and kinetic properties by several orders of magnitude. Here we report experimental observation and determination of oxide-ion vacancy concentration near the Σ13 (510)/[001] symmetric tilt grain-boundary of YSZ bicrystal using aberration-corrected TEM operated under negative spherical aberration coefficient imaging condition. We show significant oxygen deficiency due to segregation of oxide-ion vacancies near the grain-boundary core with half-width < 0.6 nm. Electron energy loss spectroscopy measurements with scanning TEM indicated increased oxide-ion vacancy concentration at the grain boundary core. Oxide-ion density distribution near a grain boundary simulated by molecular dynamics corroborated well with experimental results. Such column-by-column quantification of defect concentration in functional materials can provide new insights that may lead to engineered grain boundaries designed for specific functionalities.

No MeSH data available.


Related in: MedlinePlus

Bright-field TEM images of near-GB area investigated in this study within the range of (a) ~ 6 μm and (b) ~ 300 nm of GB.GBs are marked with red arrows on both sides. (c) Aberration-corrected TEM image taken at negative-Cs condition near Σ13(510)/[001] GB (white-dotted line) of bicrystal YSZ showing perfect registry with the simulated image in yellow inset. (d) The same aberration-corrected TEM image with oxygen columns in color code corresponding to their normalized image intensity (normalized by maximum oxygen column intensity). (e) Intensities of individual atomic columns. (f) Column intensity ratio (O/Zr) as a function of distance away from the center of the GB core (x = 0). 6 columns were counted for each data point. The error bar size is 1-standard deviation.
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f1: Bright-field TEM images of near-GB area investigated in this study within the range of (a) ~ 6 μm and (b) ~ 300 nm of GB.GBs are marked with red arrows on both sides. (c) Aberration-corrected TEM image taken at negative-Cs condition near Σ13(510)/[001] GB (white-dotted line) of bicrystal YSZ showing perfect registry with the simulated image in yellow inset. (d) The same aberration-corrected TEM image with oxygen columns in color code corresponding to their normalized image intensity (normalized by maximum oxygen column intensity). (e) Intensities of individual atomic columns. (f) Column intensity ratio (O/Zr) as a function of distance away from the center of the GB core (x = 0). 6 columns were counted for each data point. The error bar size is 1-standard deviation.

Mentions: TEM images in Figures 1(a) and (b) clearly show that the interface between the two crystals is atomically sharp without any evidence of second phase precipitation. Figure 1(c) shows an aberration-corrected TEM image taken using a spherical aberration (Cs) coefficient of –19 μm and a positive defocus of + 6 nm. Under such imaging conditions, the positions of the atoms appear bright against a dark background and the intensities of the atomic columns are directly related to their atomic numbers assuming a uniform specimen thickness78. The tilt angle (2θ) is measured to be 22.6 ± 0.1° as shown in the diffraction pattern (Figure S1), which exactly matches with the theoretical tilt angle (22.6°) of the Σ13 (510)/[001] symmetric tilt GB in a face-centered cubic (FCC) lattice crystal. The measured lattice parameter is 0.512 nm, which is in good agreement with the reported value of 0.514 nm for 8 mol% YSZ11. The atomic columns on the left side of the GB are not clearly observable, likely due to a slight misorientation of the crystal. However, due to the improved resolution of the image aberration corrector, both the cation (brighter spots) and anion columns (dimmer spots) on the right side of the GB are clearly discernable in the image.


Atomic scale verification of oxide-ion vacancy distribution near a single grain boundary in YSZ.

An J, Park JS, Koh AL, Lee HB, Jung HJ, Schoonman J, Sinclair R, Gür TM, Prinz FB - Sci Rep (2013)

Bright-field TEM images of near-GB area investigated in this study within the range of (a) ~ 6 μm and (b) ~ 300 nm of GB.GBs are marked with red arrows on both sides. (c) Aberration-corrected TEM image taken at negative-Cs condition near Σ13(510)/[001] GB (white-dotted line) of bicrystal YSZ showing perfect registry with the simulated image in yellow inset. (d) The same aberration-corrected TEM image with oxygen columns in color code corresponding to their normalized image intensity (normalized by maximum oxygen column intensity). (e) Intensities of individual atomic columns. (f) Column intensity ratio (O/Zr) as a function of distance away from the center of the GB core (x = 0). 6 columns were counted for each data point. The error bar size is 1-standard deviation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3775093&req=5

f1: Bright-field TEM images of near-GB area investigated in this study within the range of (a) ~ 6 μm and (b) ~ 300 nm of GB.GBs are marked with red arrows on both sides. (c) Aberration-corrected TEM image taken at negative-Cs condition near Σ13(510)/[001] GB (white-dotted line) of bicrystal YSZ showing perfect registry with the simulated image in yellow inset. (d) The same aberration-corrected TEM image with oxygen columns in color code corresponding to their normalized image intensity (normalized by maximum oxygen column intensity). (e) Intensities of individual atomic columns. (f) Column intensity ratio (O/Zr) as a function of distance away from the center of the GB core (x = 0). 6 columns were counted for each data point. The error bar size is 1-standard deviation.
Mentions: TEM images in Figures 1(a) and (b) clearly show that the interface between the two crystals is atomically sharp without any evidence of second phase precipitation. Figure 1(c) shows an aberration-corrected TEM image taken using a spherical aberration (Cs) coefficient of –19 μm and a positive defocus of + 6 nm. Under such imaging conditions, the positions of the atoms appear bright against a dark background and the intensities of the atomic columns are directly related to their atomic numbers assuming a uniform specimen thickness78. The tilt angle (2θ) is measured to be 22.6 ± 0.1° as shown in the diffraction pattern (Figure S1), which exactly matches with the theoretical tilt angle (22.6°) of the Σ13 (510)/[001] symmetric tilt GB in a face-centered cubic (FCC) lattice crystal. The measured lattice parameter is 0.512 nm, which is in good agreement with the reported value of 0.514 nm for 8 mol% YSZ11. The atomic columns on the left side of the GB are not clearly observable, likely due to a slight misorientation of the crystal. However, due to the improved resolution of the image aberration corrector, both the cation (brighter spots) and anion columns (dimmer spots) on the right side of the GB are clearly discernable in the image.

Bottom Line: We show significant oxygen deficiency due to segregation of oxide-ion vacancies near the grain-boundary core with half-width < 0.6 nm.Oxide-ion density distribution near a grain boundary simulated by molecular dynamics corroborated well with experimental results.Such column-by-column quantification of defect concentration in functional materials can provide new insights that may lead to engineered grain boundaries designed for specific functionalities.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA [2].

ABSTRACT
This study presents atomic scale characterization of grain boundary defect structure in a functional oxide with implications for a wide range of electrochemical and electronic behavior. Indeed, grain boundary engineering can alter transport and kinetic properties by several orders of magnitude. Here we report experimental observation and determination of oxide-ion vacancy concentration near the Σ13 (510)/[001] symmetric tilt grain-boundary of YSZ bicrystal using aberration-corrected TEM operated under negative spherical aberration coefficient imaging condition. We show significant oxygen deficiency due to segregation of oxide-ion vacancies near the grain-boundary core with half-width < 0.6 nm. Electron energy loss spectroscopy measurements with scanning TEM indicated increased oxide-ion vacancy concentration at the grain boundary core. Oxide-ion density distribution near a grain boundary simulated by molecular dynamics corroborated well with experimental results. Such column-by-column quantification of defect concentration in functional materials can provide new insights that may lead to engineered grain boundaries designed for specific functionalities.

No MeSH data available.


Related in: MedlinePlus