Oxygen isotope exchange in doped calcium and barium zirconates

• The oxygen surface exchange coefficients are measured in doped calcium and barium zirconates.
• The compensation effect is found for calcium zirconates.
• The oxygen isotope exchange is found to be limited by the incorporation stage.
• Oxygen diffusivity in calcium zirconates is limited by the grain boundaries oxygen diffusion.
• Oxygen diffusivity in barium zirconate with large grains is determined by the bulk oxygen diffusion.

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 °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 °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.