Hydration behavior of Ba2Sc2O5 with an oxygen-deficient perovskite structure

The hydration behavior of the barium scandates with oxygen-deficient perovskite-related structures of tetragonal Ba2Sc2O5 and cubic BaScO3−δ (δ ∼ 0.5) was studied. Both the tetragonal Ba2Sc2O5 and cubic BaScO3−δ absorbed water and formed Ba2Sc2O5·0.60H2O and BaScO3−δ·0.37H2O, respectively, during cooling in a humidified atmosphere. The hydration and the dehydration temperatures for the barium scandates were ∼ 533 K and ∼ 553 K, respectively; these temperatures were 30–70 K lower than that for Ba2In2O5. A distinct difference in the hydration behavior of the structurally different tetragonal Ba2Sc2O5 and cubic BaScO3−δ was not observed. The Ba2Sc2O5 shows protonic conduction below 673 K and p-type conduction above 773 K in a humidified atmosphere.