skip to main content

SciTech ConnectSciTech Connect

Title: Synthesis and characterization of R{sub 2}MnTiO{sub 7} (R = Y and Er) pyrochlores oxides

Graphical abstract: - Abstract: New pyrochlore-like phases of composition R{sub 2}MnTiO{sub 7} (R = Er and Y) have been synthesized by a soft-chemistry procedure involving citrates of the different metal ions followed by thermal treatments at moderate temperatures (850 °C for 12 h in air). A characterization by X-ray diffraction and neutron powder diffraction (NPD) has been carried out in order to determine the crystal structure features: these phyrochlores are cubic, space group Fd-3m, defining an intrinsically frustrated three-dimensional system. The Rietveld-refinement from NPD data at room temperature evidences an antisite cation disorder (distribution of Mn between A and B positions) that is accompanied by an increment of the oxygen-vacancy concentration due to the reduction of Mn{sup 4+} at the B position to Mn{sup 2+} at the A position. Thermogravimetric analysis (TGA) was useful to evaluate the stability of these oxides in reducing conditions up to 500 °C. Magnetic susceptibility measurements indicate a ferromagnetic behavior, due to the random distribution of Mn{sup 4+} ions in the octahedral sublattice. At lower temperatures there is a polarization of the R{sup +3} magnetic moments, which also participate in the magnetic structure. Aiming to evaluate these materials as possible electrodes for solid oxide fuelmore » cells (SOFC) we determined that the thermal expansion coefficients between 100 and 900 °C perfectly match with those of the usual electrolytes; however, these pyrochlore oxides display a semiconductor-like behavior with poor conductivity values, e.g. 6 × 10{sup −3} cm{sup −1} at 850 °C for Er, which would prevent its use as MIEC (mixed ionic-electronic conductors) oxides in SOFC devices.« less
Authors:
 [1] ;  [1] ;  [2]
  1. Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco E-28049, Madrid (Spain)
  2. Institut Laue Langevin, BP 156X, Grenoble, F-38042 (France)
Publication Date:
OSTI Identifier:
22341773
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 48; Journal Issue: 9; Other Information: Copyright (c) 2013 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; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CATIONS; ELECTROLYTES; HEAT TREATMENTS; MAGNETIC MOMENTS; MAGNETIC SUSCEPTIBILITY; MANGANESE IONS; NEUTRON DIFFRACTION; OXIDES; OXYGEN; POLARIZATION; PYROCHLORE; SOLID OXIDE FUEL CELLS; SYNTHESIS; THERMAL EXPANSION; THERMAL GRAVIMETRIC ANALYSIS; X-RAY DIFFRACTION