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Title: Crystal structure, microstructure and reducibility of LaNi{sub x}Co{sub 1-x}O{sub 3} and LaFe{sub x}Co{sub 1-x}O{sub 3} Perovskites (0<x<=0.5)

Abstract

Nickel and iron substituted LaCoO{sub 3} with rhombohedrally distorted perovskite structure were obtained in the temperature range of 600-900 deg. C by thermal decomposition of freeze-dried citrates and by the Pechini method. The crystal structure, morphology and defective structure of LaCo{sub 1-x}Ni{sub x}O{sub 3} and LaCo{sub 1-x}Fe{sub x}O{sub 3} were characterized by X-ray diffraction and neutron powder diffraction, TEM and SEM analyses and electron paramagnetic resonance spectroscopy. The reducibility was tested by temperature programmed reduction with hydrogen. The products of the partial and complete reduction were determined by ex-situ XRD experiments. The replacement of Co by Ni and Fe led to lattice expansion of the perovskite structure. For perovskites annealed at 900 deg. C, there was a random Ni, Fe and Co distribution. The morphology of the perovskites does not depend on the Ni and Fe content, nor does it depend on the type of the precursor used. LaCo{sub 1-x}Ni{sub x}O{sub 3} perovskites (x>0.1) annealed at 900 deg. C are reduced to Co/Ni transition metal and La{sub 2}O{sub 3} via the formation of oxygen deficient Brownmillerite-type compositions. For LaCo{sub 1-x}Ni{sub x}O{sub 3} annealed at 600 deg. C, Co/Ni metal, in addition to oxygen-deficient perovskites, was formed as an intermediate productmore » at the initial stage of the reduction. The interaction of LaCo{sub 1-x}Fe{sub x}O{sub 3} with H{sub 2} occurs by reduction of Co{sup 3+} to Co{sup 2+} prior to the Fe{sup 3+} ions. The reducibility of Fe-substituted perovskites is less sensitive towards the synthesis procedure in comparison with that of Ni substituted perovskites. - Graphical abstract: LaCo{sub 1-x}Ni{sub x}O{sub 3} and LaCo{sub 1-x}Fe{sub x}O{sub 3} with rhombohedrally distorted perovskite structure were obtained in the temperature range of 600-900 deg. C by thermal decomposition of freeze-dried La-Co/Ni(Fe)-citrates and by the Pechini method. The complete reduction of LaCo{sub 1-x}Ni{sub x}O{sub 3} with H{sub 2} proceeds to Co/Ni-metal and La{sub 2}O{sub 3}, while the interaction of LaCo{sub 1-x}Fe{sub x}O{sub 3} with H{sub 2} is not complete up to 700 deg. C. For LaCo{sub 1-x}Fe{sub x}O{sub 3}, the reaction proceeds by preferential oxidation of Co{sup 3+} to Co{sup 2+} without affecting Fe{sup 3+} ions.« less

Authors:
 [1];  [2];  [1];  [3];  [1];  [2]
  1. Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Sofia 1113 (Bulgaria)
  2. Darmstadt University of Technology, Institute of Materials Science, Structure Research, Petersenstr. 23, D-64287 (Germany)
  3. Institute of Catalysis, Bulgarian Academy of Sciences, Sofia 1113 (Bulgaria)
Publication Date:
OSTI Identifier:
21372576
Resource Type:
Journal Article
Journal Name:
Journal of Solid State Chemistry
Additional Journal Information:
Journal Volume: 183; Journal Issue: 4; Other Information: DOI: 10.1016/j.jssc.2010.02.009; PII: S0022-4596(10)00063-0; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Journal ID: ISSN 0022-4596
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ANNEALING; CITRATES; COBALT COMPOUNDS; COBALT IONS; CRYSTAL STRUCTURE; ELECTRON SPIN RESONANCE; IRON COMPOUNDS; IRON IONS; LANTHANUM OXIDES; LYOPHILIZATION; MICROSTRUCTURE; MORPHOLOGY; NEUTRON DIFFRACTION; NICKEL COMPOUNDS; OXIDATION; PEROVSKITE; PYROLYSIS; SCANNING ELECTRON MICROSCOPY; SYNTHESIS; TEMPERATURE RANGE 0400-1000 K; TEMPERATURE RANGE 1000-4000 K; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION; CARBOXYLIC ACID SALTS; CHALCOGENIDES; CHARGED PARTICLES; CHEMICAL REACTIONS; COHERENT SCATTERING; DECOMPOSITION; DIFFRACTION; ELECTRON MICROSCOPY; HEAT TREATMENTS; IONS; LANTHANUM COMPOUNDS; MAGNETIC RESONANCE; MICROSCOPY; MINERALS; OXIDE MINERALS; OXIDES; OXYGEN COMPOUNDS; PEROVSKITES; RARE EARTH COMPOUNDS; RESONANCE; SCATTERING; TEMPERATURE RANGE; THERMOCHEMICAL PROCESSES; TRANSITION ELEMENT COMPOUNDS

Citation Formats

Ivanova, S, Senyshyn, A, Zhecheva, E, Tenchev, K, Stoyanova, R, and Fuess, H. Crystal structure, microstructure and reducibility of LaNi{sub x}Co{sub 1-x}O{sub 3} and LaFe{sub x}Co{sub 1-x}O{sub 3} Perovskites (0<x<=0.5). United States: N. p., 2010. Web. doi:10.1016/j.jssc.2010.02.009.
Ivanova, S, Senyshyn, A, Zhecheva, E, Tenchev, K, Stoyanova, R, & Fuess, H. Crystal structure, microstructure and reducibility of LaNi{sub x}Co{sub 1-x}O{sub 3} and LaFe{sub x}Co{sub 1-x}O{sub 3} Perovskites (0<x<=0.5). United States. https://doi.org/10.1016/j.jssc.2010.02.009
Ivanova, S, Senyshyn, A, Zhecheva, E, Tenchev, K, Stoyanova, R, and Fuess, H. Thu . "Crystal structure, microstructure and reducibility of LaNi{sub x}Co{sub 1-x}O{sub 3} and LaFe{sub x}Co{sub 1-x}O{sub 3} Perovskites (0<x<=0.5)". United States. https://doi.org/10.1016/j.jssc.2010.02.009.
@article{osti_21372576,
title = {Crystal structure, microstructure and reducibility of LaNi{sub x}Co{sub 1-x}O{sub 3} and LaFe{sub x}Co{sub 1-x}O{sub 3} Perovskites (0<x<=0.5)},
author = {Ivanova, S and Senyshyn, A and Zhecheva, E and Tenchev, K and Stoyanova, R and Fuess, H},
abstractNote = {Nickel and iron substituted LaCoO{sub 3} with rhombohedrally distorted perovskite structure were obtained in the temperature range of 600-900 deg. C by thermal decomposition of freeze-dried citrates and by the Pechini method. The crystal structure, morphology and defective structure of LaCo{sub 1-x}Ni{sub x}O{sub 3} and LaCo{sub 1-x}Fe{sub x}O{sub 3} were characterized by X-ray diffraction and neutron powder diffraction, TEM and SEM analyses and electron paramagnetic resonance spectroscopy. The reducibility was tested by temperature programmed reduction with hydrogen. The products of the partial and complete reduction were determined by ex-situ XRD experiments. The replacement of Co by Ni and Fe led to lattice expansion of the perovskite structure. For perovskites annealed at 900 deg. C, there was a random Ni, Fe and Co distribution. The morphology of the perovskites does not depend on the Ni and Fe content, nor does it depend on the type of the precursor used. LaCo{sub 1-x}Ni{sub x}O{sub 3} perovskites (x>0.1) annealed at 900 deg. C are reduced to Co/Ni transition metal and La{sub 2}O{sub 3} via the formation of oxygen deficient Brownmillerite-type compositions. For LaCo{sub 1-x}Ni{sub x}O{sub 3} annealed at 600 deg. C, Co/Ni metal, in addition to oxygen-deficient perovskites, was formed as an intermediate product at the initial stage of the reduction. The interaction of LaCo{sub 1-x}Fe{sub x}O{sub 3} with H{sub 2} occurs by reduction of Co{sup 3+} to Co{sup 2+} prior to the Fe{sup 3+} ions. The reducibility of Fe-substituted perovskites is less sensitive towards the synthesis procedure in comparison with that of Ni substituted perovskites. - Graphical abstract: LaCo{sub 1-x}Ni{sub x}O{sub 3} and LaCo{sub 1-x}Fe{sub x}O{sub 3} with rhombohedrally distorted perovskite structure were obtained in the temperature range of 600-900 deg. C by thermal decomposition of freeze-dried La-Co/Ni(Fe)-citrates and by the Pechini method. The complete reduction of LaCo{sub 1-x}Ni{sub x}O{sub 3} with H{sub 2} proceeds to Co/Ni-metal and La{sub 2}O{sub 3}, while the interaction of LaCo{sub 1-x}Fe{sub x}O{sub 3} with H{sub 2} is not complete up to 700 deg. C. For LaCo{sub 1-x}Fe{sub x}O{sub 3}, the reaction proceeds by preferential oxidation of Co{sup 3+} to Co{sup 2+} without affecting Fe{sup 3+} ions.},
doi = {10.1016/j.jssc.2010.02.009},
url = {https://www.osti.gov/biblio/21372576}, journal = {Journal of Solid State Chemistry},
issn = {0022-4596},
number = 4,
volume = 183,
place = {United States},
year = {2010},
month = {4}
}