Abstract
In an oxygen activity gradient, BaTiO 3 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(La Ba •)-doped BaTiO 3 ceramics with different Ba/Ti ratios, Ba 1 − x La x Ti 1 − x / 4 O 3, Ba 1 − 3 x / 2 La x TiO 3 and Ba 1 − x La x TiO 3 all with x = 0.01, against oxygen activity in the range of − 15 ≤ log(Po 2/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.
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