Ba/Ti ratio effect on oxygen re-equilibration kinetics of donor-doped BaTiO3

In an oxygen activity gradient, BaTiO3 ceramic generally relaxes twofold: a fast global relaxation in the oxygen sublattice and a sluggish in-grain relaxation in the cation sublattice(s), thus allowing one to simultaneously determine the two chemical diffusivities. [Yoo et al., J. Am. Ceram. Soc., 88, 617–623 (2005)]. Upon this ground, the chemical diffusivities have been measured, by a conductivity relaxation technique, on donor(LaBa
• )-doped BaTiO3 ceramics with different Ba/Ti ratios, Ba1 − xLaxTi1 − x / 4O3, Ba1 − 3x / 2LaxTiO3 and Ba1 − xLaxTiO3 all with x = 0.01, against oxygen activity in the range of − 15 ≤ log(Po2/atm) ≤ 0 at 1200 °C. It has been found that the chemical diffusivities for the cation sublattice(s), and those for oxygen as well, are essentially the same irrespective of the Ba/Ti ratios. This fact indicates either that only either of Ba or Ti is mobile or both have about the same mobility. Circumstantial evidences support the latter.