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Title: The complex synthesis and solid state chemistry of ceria-lanthana solid solutions prepared via a hexamethylenetetramine precipitation

Abstract

Mixed oxide solid solutions are becoming ever more commercially important across a range of applications. However, their synthesis can be problematical. Here, we show that ceria-lanthana solid solutions can be readily prepared via simple precipitation using hexamethylenetetramine. However, the solution chemistry can be complex, which results in the precipitated particles having a complex structure and morphology. Great care must be taken in both the synthesis and characterisation to quantify the complexity of the product. Even very high heat treatments were not able to produce highly homogeneous materials and X-ray diffractions reveals the non-equilibrium form of particles prepared in this way. Unexpected crystal structures are revealed including a new metastable cubic La{sub 2}O{sub 3} phase. - Graphical abstract: The suggested mechanism for the formation of dual fluorite phase particles, where Step 1 corresponds to room temperature aging, Step 2; heating the solution to 90 deg. C, Step 3; cooling of the solution to room temperature, Step 4; calcination to 500 deg. C, Step 5; calcination to 700 deg. C and Step 6; calcination to 1300 deg. C. The terminology of e.g. La{sub 1-x}Ce{sub x}(OH){sub 3} is used to indicate the formation of a mixed oxy-hydroxy participate rather than a definitive assignmentmore » of stoichiometry. Similarly, La{sub 1-y}Ce{sub y}O{sub 2} only implies a mixed solid solution. Highlights: > Mol% of prepared Ce-La oxides did not follow that of reactant mol%. > Complex reaction pathway found to be dependent on metal solution concentrations. > At certain concentrations core shell particles were found to form. > A reaction model was produced based on cationic solubility. > Report lanthana solubility higher than previously reported in CeO{sub 2}.« less

Authors:
 [1];  [2];  [1];  [2];  [2];  [2];  [1];  [2];  [1];  [2];  [2];  [2]
  1. Department of Chemistry, University College Cork, Cork (Ireland)
  2. (Ireland)
Publication Date:
OSTI Identifier:
21580235
Resource Type:
Journal Article
Journal Name:
Journal of Solid State Chemistry
Additional Journal Information:
Journal Volume: 184; Journal Issue: 9; Other Information: DOI: 10.1016/j.jssc.2011.07.004; PII: S0022-4596(11)00373-2; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Journal ID: ISSN 0022-4596
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AGING; CALCINATION; CERIUM OXIDES; CRYSTAL STRUCTURE; HEAT TREATMENTS; LANTHANUM OXIDES; MATERIALS; MORPHOLOGY; PARTICLES; PRECIPITATION; SOLID SOLUTIONS; SOLIDS; SOLUBILITY; SYNTHESIS; UROTROPIN; X-RAY DIFFRACTION; AMINES; CERIUM COMPOUNDS; CHALCOGENIDES; CHEMICAL REACTIONS; COHERENT SCATTERING; DECOMPOSITION; DIFFRACTION; DISPERSIONS; HOMOGENEOUS MIXTURES; LANTHANUM COMPOUNDS; MIXTURES; ORGANIC COMPOUNDS; OXIDES; OXYGEN COMPOUNDS; PYROLYSIS; RARE EARTH COMPOUNDS; SCATTERING; SEPARATION PROCESSES; SOLUTIONS; THERMOCHEMICAL PROCESSES

Citation Formats

Fleming, P.G., E-mail: Peter.Fleming@ucc.ie, Environmental Research Institute, University College Cork, Cork, Holmes, J.D., Environmental Research Institute, University College Cork, Cork, Tyndall National Institute, Lee Maltings, Cork, CRANN, Trinity College Dublin, Dublin, Otway, D.J., Tyndall National Institute, Lee Maltings, Cork, Morris, M.A., Environmental Research Institute, University College Cork, Cork, Tyndall National Institute, Lee Maltings, Cork, and CRANN, Trinity College Dublin, Dublin. The complex synthesis and solid state chemistry of ceria-lanthana solid solutions prepared via a hexamethylenetetramine precipitation. United States: N. p., 2011. Web. doi:10.1016/j.jssc.2011.07.004.
Fleming, P.G., E-mail: Peter.Fleming@ucc.ie, Environmental Research Institute, University College Cork, Cork, Holmes, J.D., Environmental Research Institute, University College Cork, Cork, Tyndall National Institute, Lee Maltings, Cork, CRANN, Trinity College Dublin, Dublin, Otway, D.J., Tyndall National Institute, Lee Maltings, Cork, Morris, M.A., Environmental Research Institute, University College Cork, Cork, Tyndall National Institute, Lee Maltings, Cork, & CRANN, Trinity College Dublin, Dublin. The complex synthesis and solid state chemistry of ceria-lanthana solid solutions prepared via a hexamethylenetetramine precipitation. United States. doi:10.1016/j.jssc.2011.07.004.
Fleming, P.G., E-mail: Peter.Fleming@ucc.ie, Environmental Research Institute, University College Cork, Cork, Holmes, J.D., Environmental Research Institute, University College Cork, Cork, Tyndall National Institute, Lee Maltings, Cork, CRANN, Trinity College Dublin, Dublin, Otway, D.J., Tyndall National Institute, Lee Maltings, Cork, Morris, M.A., Environmental Research Institute, University College Cork, Cork, Tyndall National Institute, Lee Maltings, Cork, and CRANN, Trinity College Dublin, Dublin. Thu . "The complex synthesis and solid state chemistry of ceria-lanthana solid solutions prepared via a hexamethylenetetramine precipitation". United States. doi:10.1016/j.jssc.2011.07.004.
@article{osti_21580235,
title = {The complex synthesis and solid state chemistry of ceria-lanthana solid solutions prepared via a hexamethylenetetramine precipitation},
author = {Fleming, P.G., E-mail: Peter.Fleming@ucc.ie and Environmental Research Institute, University College Cork, Cork and Holmes, J.D. and Environmental Research Institute, University College Cork, Cork and Tyndall National Institute, Lee Maltings, Cork and CRANN, Trinity College Dublin, Dublin and Otway, D.J. and Tyndall National Institute, Lee Maltings, Cork and Morris, M.A. and Environmental Research Institute, University College Cork, Cork and Tyndall National Institute, Lee Maltings, Cork and CRANN, Trinity College Dublin, Dublin},
abstractNote = {Mixed oxide solid solutions are becoming ever more commercially important across a range of applications. However, their synthesis can be problematical. Here, we show that ceria-lanthana solid solutions can be readily prepared via simple precipitation using hexamethylenetetramine. However, the solution chemistry can be complex, which results in the precipitated particles having a complex structure and morphology. Great care must be taken in both the synthesis and characterisation to quantify the complexity of the product. Even very high heat treatments were not able to produce highly homogeneous materials and X-ray diffractions reveals the non-equilibrium form of particles prepared in this way. Unexpected crystal structures are revealed including a new metastable cubic La{sub 2}O{sub 3} phase. - Graphical abstract: The suggested mechanism for the formation of dual fluorite phase particles, where Step 1 corresponds to room temperature aging, Step 2; heating the solution to 90 deg. C, Step 3; cooling of the solution to room temperature, Step 4; calcination to 500 deg. C, Step 5; calcination to 700 deg. C and Step 6; calcination to 1300 deg. C. The terminology of e.g. La{sub 1-x}Ce{sub x}(OH){sub 3} is used to indicate the formation of a mixed oxy-hydroxy participate rather than a definitive assignment of stoichiometry. Similarly, La{sub 1-y}Ce{sub y}O{sub 2} only implies a mixed solid solution. Highlights: > Mol% of prepared Ce-La oxides did not follow that of reactant mol%. > Complex reaction pathway found to be dependent on metal solution concentrations. > At certain concentrations core shell particles were found to form. > A reaction model was produced based on cationic solubility. > Report lanthana solubility higher than previously reported in CeO{sub 2}.},
doi = {10.1016/j.jssc.2011.07.004},
journal = {Journal of Solid State Chemistry},
issn = {0022-4596},
number = 9,
volume = 184,
place = {United States},
year = {2011},
month = {9}
}