Isotope Exchange and Diffusion of Oxygen in La_0.7Sr_0.3CoO₃

E. Kh. Kurumchin, G. K. Vdovin, V. I. Tsidil’kovskii, A. N. Ezin, and Z. S. Martem’yanova

Institute of High-Temperature Electrochemistry, Ural Division, Russian Academy of Sciences,
ul. S. Kovalevskoi 20, Yekaterinburg, 620219 Russia

Received July 27, 1995

Abstract—Kinetics of the isotope exchange of oxygen between the dense La_0.7Sr_0.3CoO₃ ceramics and the
gas phase is studied at temperatures ranging from 950 to 1130 K and oxygen pressures between 0.8 and 1.6 kPa.
The interphase exchange rate R and the diffusion coefficient for oxygen isotopes D are determined. The
exchange rate as a function of temperature is described by an ordinary Arrhenius dependence of the form R
1.32 10¹⁸exp(–0.27/kT) molecules/(cm² s) (at P = 1.2 kPa). The pressure dependence of R is described by the
power equation R = R ~ p^0.5. The magnitude of the diffusion coefficient, which is expressed by the equation
D4.8 10 ⁴ exp (–0.8/kT) cm² s^–1, is virtually pressure-independent. This is attributed to a negligibly small
change in the sample stoichiometry with respect to oxygen occurring upon varying the pressure in the interval
under study.

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