The oxygen tracer diffusion coefficient and the oxygen surface exchange coefficient were measured in CaZr1-xScxO3-x/2 (x = 0, 0.01, 0.05) and BaZr0.8Y0.2O2.9 zirconates over the temperature range of 700-900 degrees C and the oxygen pressure range of 0.13-6.67 kPa using the oxygen isotope exchange method with gas phase equilibration. The dependence of oxygen exchange coefficient on scandium content reduces gradually with temperature increasing, in the way that at 850 degrees C the oxygen exchange coefficient becomes almost independent on scandium concentration in calcium zirconates. The oxygen isotope exchange is found to be limited by the incorporation stage. Influence of grain boundaries on the oxygen diffusivity in calcium and barium zirconates is discussed. (C) 2016 Elsevier B.V. All rights reserved.