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Development and Validation of Chromium Getters for Solid Oxide Fuel Cell Power Systems
Published on: May 26, 2019
Co-doping of scandia-zirconia electrolytes for SOFCs
John T S Irvine1, Jeremy W L Dobson, Tatiana Politova
1University of St Andrewis, School of Chemistry, St. Andrews, Scotland, UK.
Faraday Discussions
|March 1, 2007
Summary
Scandia stabilized zirconia shows improved electrical performance for fuel cells. Adding yttria and ceria enhances stability and conductivity, making it a viable commercial option despite cost uncertainties.
Area of Science:
- Materials Science
- Electrochemistry
- Solid-State Chemistry
Background:
- Scandia stabilized zirconia (ScSZ) offers superior electrical performance compared to yttria stabilized zirconia (YSZ) for fuel cell applications.
- Historically, scandia's high cost and limited availability hindered its commercial adoption.
- Recent geopolitical and economic shifts have increased scandia availability, prompting re-evaluation for commercial use.
Purpose of the Study:
- To investigate the impact of small yttria additions on the phase stability and electrical conductivity of scandia stabilized zirconia.
- To explore the role of ceria in mitigating conductivity reduction caused by yttria.
- To understand the relationship between composition, short-range ordering, and ionic conductivity in these materials.
Main Methods:
- Synthesis and characterization of scandia-yttria-zirconia (S Y Z) and scandia-yttria-ceria-zirconia (SYCZ) materials.
- Electrical conductivity measurements using impedance spectroscopy across a range of temperatures.
- Phase analysis using X-ray diffraction (XRD) and structural studies using neutron and electron diffraction.
Main Results:
- A small addition of 2 mol% yttria stabilizes the cubic phase of zirconia, preventing detrimental phase changes during thermal cycling.
- Yttria addition slightly reduces electrical conductivity, but this effect can be reversed by further addition of ceria.
- Arrhenius plots reveal two linear conductivity regions; activation energies are composition-dependent, correlating with short-range order strength.
Conclusions:
- Scandia stabilized zirconia, particularly when co-doped with yttria and ceria, presents a promising material for solid oxide fuel cell electrolytes due to enhanced phase stability and tunable electrical properties.
- The observed changes in activation energy are linked to the ionic size of Sc and Zr, influencing short-range ordering and coordination numbers within the fluorite structure.
- Further research into optimizing composition and processing is warranted to fully realize the commercial potential of these advanced zirconia electrolytes.
