Water incorporation into the Ba2(In1 − xMx)2O5 (M = Sc3+ 0 ≤ x < 0.5 and M = Y3+ 0 ≤ x < 0.35) system and protonic conduction
Abstract Ba 2 (In 1 −  x M x ) 2 O 5 −  y  / 2 (OH) y ‪□ 1 −  y  / 2 ( y  ≤ 2; M = Sc 3+ 0 ≤  x 3+ 0 ≤  x 2 (In 1 −  x M x ) 2 O 5 ‪ phases with water vapor. This reaction is reversible. Analyses of the hydration process by TG and XRD studies show that the thermal stability of hydrated phases increases when x increases and that the incorporation of water is not a single-phase reaction inducing either a crystal system or space group modification. Fully hydrated ( y  = 2) and dehydrated ( y  = 0) samples have been stabilized at room temperature and characterized for all compositions. In wet air, all phases show a proton contribution to the total conductivity at temperatures between 350 and 600 °C. At a given temperature, proton conductivity increases with the substitution ratio and reaches at 350 °C, 5.4 10 − 3 S cm − 1 for Ba 2 (In 0.65 Sc 0.35 ) 2 O 4.2 □ 0.2 (OH) 1.6 .