The electrochemical determination of oxygen ion diffusion coefficients in La0.50Sr0.50CoO3?y: Experimental results and related properties

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) 10³/T?(6.6±0.6) cm² 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/H₂ (1 atm) electrode in the same solution) and Δy is found: E=627–108 ln (Δy + 0.0054) mV. (Δy=y?y₀; y₀=mole fraction of vacancies at the reversible O₂ 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.