Structural Competition and Reactivity of Rare-Earth Oxide Phases in Y_xPr_2–xO₃(0.05 ≤ x ≤ 0.80)

Journal Article · Fri Oct 26 00:00:00 EDT 2018 · Inorganic Chemistry

DOI:https://doi.org/10.1021/acs.inorgchem.8b01911· OSTI ID:1484775

Lussier, Joey A.  ^[1]; Souza, Diego H. P. ^[2]; Whitfield, Pamela S. ^[3]; Bieringer, Mario  ^[1]

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1. Univ. of Manitoba, Winnipeg, MB (Canada)
2. Univ. of Manitoba, Winnipeg, MB (Canada); Ministry of Education of Brazil, Brasilia, (Brazil). CAPES Foundation
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)

We report, for the first time, members of the Y_xPr_2–xO₃ system with non-bixbyite or defect fluorite structures. The synthesis, structure, phase transitions, and high temperature reactivity of the trigonal A-type and monoclinic B-type structures are reported along with those of the cubic C-type phase (bixbyite). Combined powder X-ray and neutron diffraction Rietveld refinements are used to report structural details of all three reported phases. Phase transitions are investigated, showing a clear dependence on average cation size. Using neutron diffraction, phase transitions are followed in situ, revealing that all high temperature phases are quenchable. In-situ powder X-ray diffraction experiments in flowing oxygen allow insights into mechanistic details of redox processes in the reported phases. In contrast to the C-type cubic bixbyite, the trigonal A-type and monoclinic B-type structures do not allow for topotactic oxygen uptake, displaying instead a phase transition to either the bixbyite C-type capable of accommodating additional oxide anions or the direct oxidation to the cubic defect fluorite structure. The findings reported here agree with the accepted lanthanide sesquioxide phase diagrams and provide exceptional control of phases. The work is important for the prediction of structures, and the synthetic control needed for rational design of functional materials.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: Natural Sciences and Engineering Research Council of Canada (NSERC); Canada Foundation for Innovation (CFI); Major Innovation Fund (MIF); University of Manitoba; Science without Borders Program; USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1484775
• Journal Information: Inorganic Chemistry, Vol. 57, Issue 22; ISSN 0020-1669
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Granular materials
Chemical structure
Physical and chemical processes
Phase transitions
Cations