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Description
Mehmet Kilic1 Aloysius Soon1

1, Yonsei University, Seoul, , Korea (the Republic of)

Solid oxide fuel cells (SOFC) are electrochemical devices that convert chemical energy into electrical energy. SOFC consist of three main elements, i.e., the cathode, the electrolyte, and the anode. The electrolyte must be stable in reducing and oxidizing environments in addition to high ionic conductivity with low electronic conductivity. Zirconia-based ceramics as fluorite structure oxide have been the most favored electrolyte with high ion conductivity for SOFC. Even though yttria-stabilized zirconia (YSZ) and scandia-stabilized zirconia (ScSZ) are typically used for the SOFC at high temperatures, their performance is not optimal at operating temperatures with respect to ionic conductivity and stabilization respectively. Many works on ion-diffusion have been concentrated in bulk YSZ and ScSZ systems. However, to improve the ionic conductivity and stability of electrolyte materials, it is an essential to seek more sustainable alternative systems such as heterogeneous doping and heterolayer structures. In this work, we consider three main mechanisms contributing to the enhancement of ionic diffusion at the interface: 1) the influence of cation distribution, 2) the nature of the interfaces, and 3) the influence of the crystal structure. For these considerations, different possible compositions of YSZ/ScSZ systems (within the superlattice model) have been performed using classical molecular dynamics simulations in this work. Our main research objective is to examine the oxygen ion diffusion mechanism in the vicinity of the YSZ/ScSZ interface. Additionally, several physical properties (namely, the relative energies and radial distribution function for pairs of ions) of these systems are systematically studied as a function of cation distribution and temperatures. A linear relation has been found between the mean square displacement and time, from which the ion diffusion coefficient is calculated. The respective activation energies and diffusion coefficients agree well with experimental findings.

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