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Topological metastability and oxide ionic conduction in La(2)-(x)Eu(x)Mo(2)O(9).
Gwenaël Corbel1, Elodie Chevereau, Stéphanie Kodjikian
1Laboratoire des Oxydes et Fluorures, UMR-6010 CNRS, Université du Maine, Avenue Olivier Messiaen, Le Mans Cedex 9, France. gwenael.corbel@univ-lemans.fr
Inorganic Chemistry
|July 5, 2007
Summary
Europium substitution in La2Mo2O9 influences phase stability and transport properties. Higher europium content stabilizes the cubic beta phase, affecting conductivity across different temperature regimes.
Area of Science:
- Solid-state chemistry
- Materials science
- Ionic conductivity
Background:
- Lanthanum Molybdate (La2Mo2O9) is a material with potential applications in solid oxide fuel cells.
- Understanding the impact of aliovalent substitutions is crucial for optimizing its properties.
Purpose of the Study:
- Investigate the effect of trivalent Europium (Eu) substitution for Lanthanum (La) on the phase stability and transport properties of La2Mo2O9.
- Determine how Eu content influences the structural phase transitions and ionic conductivity.
Main Methods:
- Temperature-controlled X-ray powder diffraction (XRD) for phase analysis.
- Differential thermal analysis (DTA) to study phase transitions.
- Complex impedance spectroscopy to evaluate electrical transport properties.
Main Results:
- Partial substitution of La by Eu (up to x = 0.4) affects the alpha-beta phase transition temperature and stability.
- Low Eu content (x ≤ 0.1) shows a shaping-dependent transition; high Eu content (x ≥ 0.25) stabilizes the cubic beta phase.
- Intermediate Eu content (x = 0.15, 0.2) exhibits complex phase behavior sensitive to thermal history and shaping.
- Ionic conductivity analysis reveals distinct Arrhenius and Vogel-Tammann-Fulcher (VTF) regimes, with an abrupt change in parameters between alpha and beta phases.
Conclusions:
- Europium substitution significantly impacts the phase diagram and thermal expansion of La2Mo2O9.
- The crystallographic phase (alpha vs. beta) strongly influences the ionic transport mechanisms and conductivity parameters.
- Optimizing Eu content and processing conditions is key to tailoring the material's properties for specific applications.
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