Origin of fast oxide ion diffusion along grain boundaries in Sr-doped LaMnO3

2018 ◽  
Vol 20 (28) ◽  
pp. 19142-19150 ◽  
Author(s):  
Jonathan M. Polfus ◽  
Bilge Yildiz ◽  
Harry L. Tuller
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Ion Diffusion ◽  
Oxide Ion ◽  
Boundary Core

Enhanced oxide ion diffusion by 3 to 5 orders of magnitude along grain boundary core in Sr-doped LaMnO3.

scholarly journals Fast oxygen exchange and diffusion kinetics of grain boundaries in Sr-doped LaMnO3 thin films

2015 ◽  
Vol 17 (12) ◽  
pp. 7659-7669 ◽  
Author(s):  
Edvinas Navickas ◽  
Tobias M. Huber ◽  
Yan Chen ◽  
Walid Hetaba ◽  
Gerald Holzlechner ◽  
...  
Keyword(s):  
Thin Films ◽  
Oxygen Reduction Reaction ◽  
Grain Boundaries ◽  
Isotope Exchange ◽  
Reduction Reaction ◽  
Diffusion Kinetics ◽  
Ion Diffusion ◽  
Kinetics Of ◽  
And Diffusion ◽  
Oxide Ion

Isotope exchange depth profile measurements were performed on columnar/epitaxial LSM thin films with varied microstructure. These uncover the importance of grain boundaries for oxygen reduction reaction and oxide ion diffusion.

scholarly journals Electrochemical drag effect on grain boundary motion in ionic ceramics

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
K. S. N. Vikrant ◽  
Wolfgang Rheinheimer ◽  
R. Edwin García
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Driving Forces ◽  
Ionic Species ◽  
Boundary Motion ◽  
Wide Range ◽  
Structural Interface ◽  
Applied Fields ◽  
Grain Boundary Motion ◽  
Boundary Core

Abstract The effects of drag imposed by extrinsic ionic species and point defects on the grain boundary motion of ionic polycrystalline ceramics were quantified for the generality of electrical, chemical, or structural driving forces. In the absence of, or for small driving forces, the extended electrochemical grain boundary remains pinned and symmetrically distributed about the structural interface. As the grain boundary begins to move, charged defects accumulate unsymmetrically about the structural grain boundary core. Above the critical driving force for motion, grain boundaries progressively shed individual ionic species, from heavier to lighter, until they display no interfacial electrostatic charge and zero Schottky potential. Ionic p–n junction moving grain boundaries that induce a finite electrostatic potential difference across entire grains are identified for high velocity grains. The developed theory is demonstrated for Fe-doped SrTiO3. The increase in average Fe concentration and grain boundary crystallographic misorientation enhances grain boundary core segregation and results in thick space charge layers, which leads to a stronger drag force that reduces the velocity of the interface. The developed theory sets the stage to assess the effects of externally applied fields such as temperature, electromagnetic fields, and chemical stimuli to control the grain growth for developing textured, oriented microstructures desirable for a wide range of applications.

Open Questions in Nanosegregation

2017 ◽  
Vol 891 ◽  
pp. 3-10
Author(s):  
Pavel Lejček
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Segregation ◽  
Theoretical Data ◽  
Grain Boundary Segregation ◽  
The Past ◽  
Open Questions ◽  
Experimental Values ◽  
Boundary Core

Despite nanosegregation of solutes at grain boundaries has been intensively studied in the past decades and numerous theoretical data as well as experimental values on characteristic energies and/or enthalpies and entropies exist some questions remain still unanswered. In this paper some of these questions – Which energetic quantities obtained in different ways, experimentally and theoretically, can be mutually compared? What is the segregation site of a solute in the grain boundary core? – are discussed in more detail. It will be shown that the entropy of grain boundary segregation plays an important and indisputable role in responding some issues and that understanding of its role will help us to elucidate fundamentals of the grain boundary segregation.

Atomic-Scale Grain Boundary Relaxation Modes in Metals and Ceramics

1997 ◽  
Vol 3 (4) ◽  
pp. 339-351 ◽  
Author(s):  
K.L. Merkle
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Energy State ◽  
High Resolution Electron Microscopy ◽  
Atomic Scale ◽  
Relaxation Processes ◽  
Geometrical Constraints ◽  
Boundary Properties ◽  
Fcc Materials ◽  
Boundary Core

Abstract: The atomic-scale structure of tilt grain boundaries has been studied by high-resolution electron microscopy (HREM) in several ceramics and metals such as NiO, yttria stabilized zirconia, Au, and Al. It is found that when grain boundaries are formed between two crystals a considerable variety of modes of relaxations, i.e., the rearrangements of atoms in and near the grain boundary core are possible, depending on grain boundary geometry and the interatomic interactions. The atomic relaxations within and near the grain boundary core often include relaxations that involve the formation of stacking faults in low-stacking-fault energy fcc materials. Grain boundary dissociations are also observed for several grain boundary geometries. Computer simulations of grain boundary structures in metals have in general been able to reproduce the relaxation features at least on a qualitative level. In contrast, ceramic grain boundaries typically are more complex and not always tractable by simple computer relaxation procedures, since the formation of point defects and partial occupancy of atomic columns may be involved in the relaxation processes. It is found that when a boundary is not allowed to relax to its lowest energy state due to geometrical constraints, a multitude of grain boundary core structures can exist. Such conditions are expected to be characteristic for nanocrystalline materials. Because of its close connection to grain boundary properties, quantification of the volume expansion by HREM techniques is an important goal of grain boundary research. Image simulations of grain boundaries suggest that for most materials of interest the 3-fold astigmatism must be corrected to better than 100 nm to achieve the desired accuracies.

Mössbauer Investigations of Grain-Boundary Diffusion and Segregation

2006 ◽  
Vol 258-260 ◽  
pp. 497-508 ◽  
Author(s):  
Vladimir V. Popov
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
Diffusion Mechanism ◽  
Boundary Segregation ◽  
Grain Boundary Diffusion ◽  
Grain Boundary Segregation ◽  
Emission Mössbauer Spectroscopy ◽  
Diffusion Profiles ◽  
Boundary Core

Possibilities of grain-boundary diffusion and segregation studies using nuclear gammaresonance spectroscopy (NGR) are considered. It is shown that the results of the Mössbauer investigations testify the necessity to specify the classical Fisher’s model of grain-boundary diffusion, and a possible way of such specification is suggested. It is demonstrated that investigation of grain boundaries using emission Mössbauer spectroscopy appreciably supplement the information obtained from the diffusion profiles analysis. In particular, Mössbauer investigations make it possible to evaluate directly the grain-boundary segregation factor, to determine the grain-boundary diffusion mechanism, to estimate the rate of the diffusant pumping from a grain boundary core into the bulk, etc.

Sign in / Sign up

Export Citation Format

Share Document