Abstract
Results of an electrochemical method for the determination of oxygen ion diffusion coefficients D O 2− in porous pellets of La 0.50Sr 0.50CoO 3−y are presented. Log D O 2− can be expressed as log D O 2− =−(2.3±0.2) 10 3/ T−(6.6±0.6) cm 2 s −1. The activation energy E a for the diffusion process equals 44 kJ mol −1. Further the related electrochemical measurement and the adjustment of the oxygen deficiency y are described. At 75°C the following empirical Nernst relation between the electrode potential E (vs. a Pt/H 2 (1 atm) electrode in the same solution) and Δ y is found: E=627–108 ln (Δ y + 0.0054) mV. (Δ y= y−y 0 ; y 0=mole fraction of vacancies at the reversible O 2 potential of 1190 mV). The use of La 0.50Sr 0.50CoO 3−y as a solid solution electrode in practical storage cells seems to be excluded for thermodynamic and kinetic reasons.
Published Version
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