The mechanism and kinetics of water incorporation into the double perovskites was investigated at 300 to 500C, for aH2O = 10−3 to 2.2 x 10−2. The formation of hydration products, Ba4Ca2Nb2O11xH2O and Sr6Ta2O11xH2O (0.2 < x < 0.50) was limited by the diffusion of H2O. It was found that the concentration dependences of DH2O were the same for both samples. That is, there was a small increase in DH2O with increasing x. The temperature dependences of the chemical diffusion coefficients of water for Ba4Ca2Nb2O110.35H2O and Sr6Ta2O110.35H2O could be described by activation energies of 0.38 and 0.49eV, respectively. The chemical diffusion coefficients of water were nearly an order of magnitude smaller for Sr6Ta2O11. This was consistent with lower O and proton conductivities in Sr6Ta2O11; as a consequence of lower mobilities.

Chemical Diffusion of Water in the Double Perovskites Ba4Ca2Nb2O11 and Sr6Ta2O11. I.Animitsa, A.Neiman, N.Kochetova, D.Korona, A.Sharafutdinov: Solid State Ionics, 2006, 177[26-32], 2363-8