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Title: Structural investigations of La 0.6Sr 0.4FeO 3-δ under reducing conditions: kinetic and thermodynamic limitations for phase transformations and iron exsolution phenomena

Abstract

The crystal structure changes and iron exsolution behavior of a series of oxygen-deficient lanthanum strontium ferrite (La 0.6Sr 0.4FeO 3-δ, LSF) samples under various inert and reducing conditions up to a maximum temperature of 873 K have been investigated to understand the role of oxygen and iron deficiencies in both processes. Iron exsolution occurs in reductive environments at higher temperatures, leading to the formation of Fe rods or particles at the surface. Utilizing multiple ex situ and in situ methods (in situ X-ray diffraction (XRD), in situ thermogravimetric analysis (TGA), and scanning X-ray absorption near-edge spectroscopy (XANES)), the thermodynamic and kinetic limitations are accordingly assessed. Prior to the iron exsolution, the perovskite undergoes a nonlinear shift of the diffraction peaks to smaller 2θ angles, which can be attributed to a rhombohedral-to-cubic (R$$\overline{3}$$c to Pm$$\overline{3}$$m) structural transition. In reducing atmospheres, the cubic structure is stabilized upon cooling to room temperature, whereas the transition is suppressed under oxidizing conditions. This suggests that an accumulation of oxygen vacancies in the lattice stabilize the cubic phase. The exsolution itself is shown to exhibit a diffusion-limited Avrami-like behavior, where the transport of iron to the Fe-depleted surface-near region is the rate-limiting step.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [3];  [1];  [1];  [4];  [4];  [5];  [2];  [1]; ORCiD logo [1]
  1. University of Innsbruck (Austria)
  2. Technical University Berlin (Germany)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  4. Nagoya University, Furo-cho, Chikusa-ku (Japan)
  5. RIKEN SPring-8 Center, Sayo (Japan)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1485071
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
RSC Advances
Additional Journal Information:
Journal Volume: 8; Journal Issue: 6; Journal ID: ISSN 2046-2069
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Götsch, Thomas, Schlicker, Lukas, Bekheet, Maged F., Doran, Andrew, Grünbacher, Matthias, Praty, Corsin, Tada, Mizuki, Matsui, Hirosuke, Ishiguro, Nozomu, Gurlo, Aleksander, Klötzer, Bernhard, and Penner, Simon. Structural investigations of La0.6Sr0.4FeO3-δ under reducing conditions: kinetic and thermodynamic limitations for phase transformations and iron exsolution phenomena. United States: N. p., 2018. Web. doi:10.1039/c7ra12309d.
Götsch, Thomas, Schlicker, Lukas, Bekheet, Maged F., Doran, Andrew, Grünbacher, Matthias, Praty, Corsin, Tada, Mizuki, Matsui, Hirosuke, Ishiguro, Nozomu, Gurlo, Aleksander, Klötzer, Bernhard, & Penner, Simon. Structural investigations of La0.6Sr0.4FeO3-δ under reducing conditions: kinetic and thermodynamic limitations for phase transformations and iron exsolution phenomena. United States. doi:10.1039/c7ra12309d.
Götsch, Thomas, Schlicker, Lukas, Bekheet, Maged F., Doran, Andrew, Grünbacher, Matthias, Praty, Corsin, Tada, Mizuki, Matsui, Hirosuke, Ishiguro, Nozomu, Gurlo, Aleksander, Klötzer, Bernhard, and Penner, Simon. Mon . "Structural investigations of La0.6Sr0.4FeO3-δ under reducing conditions: kinetic and thermodynamic limitations for phase transformations and iron exsolution phenomena". United States. doi:10.1039/c7ra12309d. https://www.osti.gov/servlets/purl/1485071.
@article{osti_1485071,
title = {Structural investigations of La0.6Sr0.4FeO3-δ under reducing conditions: kinetic and thermodynamic limitations for phase transformations and iron exsolution phenomena},
author = {Götsch, Thomas and Schlicker, Lukas and Bekheet, Maged F. and Doran, Andrew and Grünbacher, Matthias and Praty, Corsin and Tada, Mizuki and Matsui, Hirosuke and Ishiguro, Nozomu and Gurlo, Aleksander and Klötzer, Bernhard and Penner, Simon},
abstractNote = {The crystal structure changes and iron exsolution behavior of a series of oxygen-deficient lanthanum strontium ferrite (La0.6Sr0.4FeO3-δ, LSF) samples under various inert and reducing conditions up to a maximum temperature of 873 K have been investigated to understand the role of oxygen and iron deficiencies in both processes. Iron exsolution occurs in reductive environments at higher temperatures, leading to the formation of Fe rods or particles at the surface. Utilizing multiple ex situ and in situ methods (in situ X-ray diffraction (XRD), in situ thermogravimetric analysis (TGA), and scanning X-ray absorption near-edge spectroscopy (XANES)), the thermodynamic and kinetic limitations are accordingly assessed. Prior to the iron exsolution, the perovskite undergoes a nonlinear shift of the diffraction peaks to smaller 2θ angles, which can be attributed to a rhombohedral-to-cubic (R$\overline{3}$c to Pm$\overline{3}$m) structural transition. In reducing atmospheres, the cubic structure is stabilized upon cooling to room temperature, whereas the transition is suppressed under oxidizing conditions. This suggests that an accumulation of oxygen vacancies in the lattice stabilize the cubic phase. The exsolution itself is shown to exhibit a diffusion-limited Avrami-like behavior, where the transport of iron to the Fe-depleted surface-near region is the rate-limiting step.},
doi = {10.1039/c7ra12309d},
journal = {RSC Advances},
number = 6,
volume = 8,
place = {United States},
year = {2018},
month = {1}
}

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