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Title: Phase transitions of BaTi{sub 0.9}Rh{sub 0.1}O{sub 3±δ} perovskite-type oxides under reducing environments

Highlights: • Solid solution formation BaTi{sub 0.9}Rh{sub 0.1}O{sub 3±δ} with a new wet chemical synthesis method. • Rhodium in the BaTiO{sub 3} perovskite stabilizes the hexagonal structure. • New Rh segregation mechanism for hexagonal BaTi{sub 0.9}Rh{sub 0.1}O{sub 3±δ} upon reduction. - Abstract: Perovskite-type oxides of composition BaTi{sub 0.9}Rh{sub 0.1}O{sub 3±δ} were prepared following a new chemical route that avoids the formation of hydroxyl species and precipitation, and allows the homogeneous distribution of Rh in the final mixed metal oxide. The high dispersion of Rh and the formation of the solid solution between Rh and the BaTiO{sub 3} perovskite is confirmed by means of X-ray diffraction (XRD) and extended X-ray absorption fine structure spectroscopy (EXAFS). The presence of Rh stabilized the hexagonal BaTi{sub 0.9}Rh{sub 0.1}O{sub 3±δ} phase, which decomposes into barium orthotitanate (BaTi{sub 2}O{sub 4}) and metallic Rh° in reducing environment. This phase transition starts already at 700 °C and is only partially completed at 900 °C suggesting that part of the Rh present in the perovskite lattice might not be easily reduced by hydrogen. These aspects and further open questions are discussed.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1]
  1. German Aerospace Center (DLR), Institute of Materials Research, Linder Hoehe, D-51147 Cologne (Germany)
  2. Institute of Inorganic Chemistry, University of Cologne (Germany)
  3. Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland)
  4. Empa, Swiss Federal Laboratories for Materials Science and Technology, Lab. for Solid State Chemistry and Catalysis, Ueberlandstrasse 129, CH-8600 Dübendorf (Switzerland)
  5. UTN-Facultad Regional Santa Cruz, Av. Inmigrantes 555, Río Gallegos, 9400 Santa Cruz (Argentina)
Publication Date:
OSTI Identifier:
22420749
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 61; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; BARIUM COMPOUNDS; FINE STRUCTURE; HYDROGEN; HYDROXIDES; MICROSTRUCTURE; PEROVSKITE; PHASE TRANSFORMATIONS; PRECIPITATION; REDUCTION; RHODIUM OXIDES; SEGREGATION; SOLID SOLUTIONS; SYNTHESIS; TITANATES; X-RAY DIFFRACTION; X-RAY SPECTROSCOPY