7 Scopus citations

Abstract

In this work, the Pechini method was used to synthesize La0.7−xLnxCa0.3MnO3,(Ln=ProrSm)-La1−xLnxCa0.3MnO3 type perovskites, evaluating the effect of the type of cation and composition on the structural, morphological and textural properties. The use of similar rare earth cations was studied to promote weak bonds between the reactive surface and adsorbed oxygen species that could facilitate the oxygen reduction reaction and thus improve electrochemical performance of SOFC devices. To achieve this goal, different compositions of Pr or Sm ions (x = 0.1, 0.3, 0.5 or 0.6) were used for the partial substitution of lanthanum at the A site. The results indicated that the substitution of La by Pr or Sm did not modify the original orthorhombic perovskite structure of Ca-doped lanthanum manganites. However, a shift in the main reflections can be obtained as the content of both cations increases due to cell distortion. Rietveld refinement confirms that the crystal structure belongs to the Pnma space group with a large distortion along the b-axis but no secondary phase formation. The compensated charge neutrality of the Mn3+/Mn4+ ratio influences the octahedral sites of MnO6 and cell volume. Orthorhombic distortion ([Formula presented]) occurs through Jahn-Teller mechanism promoting a hole-doped system for electrical conductivity. The adsorption-desorption isotherms reveal that in any composition of Pr, a mesoporous isotherm (type IV) is obtained. In contrast, the isotherms changed from micro- to meso-porous features depending on the amount of Sm substitution at the A-site. All the prepared samples showed a soft granular structure with agglomerates ranging between 200 and 300 nm with well-interconnected pores. Comparing the La substitution by Pr or Sm, it was found that Sm can form perovskites that can better promote oxygen vacancies and triple boundary phase formation, which is essential in SOFC devices.

Original languageEnglish
Pages (from-to)21221-21234
Number of pages14
JournalCeramics International
Volume48
Issue number15
DOIs
StatePublished - 1 Aug 2022

Keywords

  • Microstructural analysis
  • Pechini method
  • Perovskites
  • Pr and Sm rare Earth ions
  • Solid state fuel cells

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