The kinetics and mechanism of water incorporation into binary perovskite (elpasolite) Ba4Ca2Nb2O11 were studied at 300 to 500C, for aH2O = 10−3 to 2.2 x 10−2. The product of hydration, at these temperatures and values of aH2O, was a solid solution having the composition: Ba4Ca2Nb2O11xH2O (x < 0.5). The process of interaction with water vapor was shown to be limited by the intraphase diffusion of H-and O-containing species that entered the composition of H2O. The coefficients of chemical diffusion of water, DH2O, were estimated from the relaxation dependences of the weight during stage-by-stage changes in humidity log[aH2O] = -3.0 → -2.5 → -2.0 → -1.6. It was established that the coefficient of chemical diffusion of water for Ba4Ca2Nb2O11xH2O at 0.1 < x < 0.5 increased insignificantly with increasing x. The chemical diffusion of water for the composition Ba4Ca2Nb2O11▪0.35H2O was characterized by an activation energy of 0.38eV. Given the joint transfer of O2− and H+, the latter value suggested that protons could exert an influence upon the rate and energy of O migration. Possible forms of proton-containing species in the case of migration in experiments on chemical diffusion were considered.

Intraphase Chemical Diffusion of Water in Ba4Ca2Nb2O11. I.E.Animitsa, A.Y.Neiman, N.A.Kochetova, D.V.Korona: Russian Journal of Electrochemistry, 2006, 42[4], 311-9