The novel Zn-doped hexagonal perovskite Ba7In6Al2O19: electrical conductivity and hydration

Abstract

The novel phase Ba7In5.9Zn0.1Al2O18.95 with hexagonal perovskite structure was obtained by solid-state technique. The substitution of In3+ by the Zn2+ leads to the expansion of the lattice parameters and cell volume. It was established that the investigated sample is capable of water incorporation from the gas phase; the degree of hydration reaches 1.42 mol H2O, which is significantly higher than that for the undoped phase (0.41 mol H2O). This is a result of the expansion of the hexagonal layer that facilitates the placement of OH–-groups. The oxide-ion and proton conductivities for the doped Ba7In5.9Zn0.1Al2O18.95 sample were higher than those for the undoped composition, Ba7In6Al2O19, by 0.50 and 0.75 orders of magnitude (500 °C), respectively. The new phase Ba7In5.9Zn0.1Al2O18.95 demonstrates the predominant protonic conductivity at Т ≤ 500 °C and pH2O = 1.93·10−2 atm.

Keywords

• hexagonal perovskite
• proton conductivity
• hydration
• transport numbers