The chemical diffusion and surface exchange coefficients were measured for SrFeO3-delta, La(0.5)Sr(0.5)feO(3-delta), and La(0.2)Sr(0.8)Cr(0.2)fe(0.8)O(3)-(delta) at 790 <= T <= 1000 degrees C and 0.01 <= pO(2) <= 1 atm by electrical conductivity relaxation. Values of the chemical diffusion (D-chem) and surface exchange (k(chem)) coefficients were obtained by monitoring the variation of electrical conductivity after an abrupt change in oxygen partial pressure. The vacancy diffusion coefficient (D-v), oxygen ion self-diffusion coefficient (D-o), and surface exchange coefficients at thermal equilibrium (k(ex)) were calculated using the measured thermodynamic factors and were compared with literature data for other compositions. (c) 2005 The Electrochemical Society. [DOI: 10. 1149/1.1854617] All rights reserved.