Specific structural features of LnZrOx (Ln: La, Sm) mixed oxides prepared by different methods

Tatyana Kuznetsova, Tamara Kriger, Yurii Chesalov, Andrey Boronin, Arcadii Ishchenko, Pavlos K. Pandis, Vladimir Krivensov, Galina Litvak, Tatyana Larina, Vladislav Sadykov, Vassilis N. Stathopoulos

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

LnZrOx (Ln: La, Sm) mixed oxides of Ln: Zr = 1 were prepared by different methods (complex polymerized method, sorption of cations on starch from aqueous salt solution and conventional co-precipitation with additional redispersion of precipitate by ultra sound) and calcined at 700–1300 °C. Their specific structural features and changes were studied and discussed. Various characterization methods were used such as X-ray diffraction, Electron microscopy, Fourier-transform infrared and Raman spectroscopy, UV–Vis spectroscopy, X-Ray absorption fine structure and X-ray photoelectron spectroscopy. The formation of pyrochlore structure occurred at 1100–1300 °C from fluorite-like pseudocubic phase ZrO2 regardless the method of preparation. This phase had a block-like structure consisting of ZrO2 nanocrystals stabilized by Ln cations and residual anions such as hydroxyls and carbonates. The desorption of such anions with heating already started at 900 °C and lead to local changes of Zr cations coordination to octahedral and to the formation of pyrochlore nanodomains inclusions within fluorite-like phase. The increased cation mobility and further elimination of anions caused by further heating was accompanied by the formation of bulk pyrochlore phase at 1100–1300 °C. Even after calcination at 1300 °C the local microheterogeneity as well as defects were identified at domains boundaries or sintered microstructure. These specific features of the formed pyrochlores depend on the method of preparation.

Original languageEnglish
Pages (from-to)437-446
Number of pages10
JournalProgress in Natural Science: Materials International
Volume28
Issue number4
DOIs
Publication statusPublished - 1 Aug 2018

Keywords

  • Fluorites
  • Powders
  • Pyrochlores
  • Structure
  • Synthesis
  • ZIRCONIA
  • NONSTOICHIOMETRY
  • MECHANICAL-PROPERTIES
  • CO OXIDATION
  • SMFE1-XALXO3 X=0.00
  • TEMPERATURE
  • THERMAL BARRIER COATINGS
  • LN(2)ZR(2)O(7) LN
  • GD
  • CERAMICS

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