Transport Properties of In3+- and Y3+-Doped Hexagonal Perovskite Ba5In2Al2ZrO13

A complex oxide Ba5In1.9Y0.1Al2ZrO13 with hexagonal perovskite structure (a = 5.971(4) angstrom, c = 24.012(1) angstrom) is prepared for the first time. The phase is found to dissociative-absorb water from gas phase, the degree of hydration being as high as 0.39 mol H2O. It was found by using IR-spectroscopy that protons are present therein as energetically nonequivalent OH--groups involved in hydrogen bonds of diverse strength. Isovalent yttrium-doping of the Ba5In2Al2ZrO13 phase is shown not to lead to any valuable change in the oxygen-ion-conductivity as compared with the Ba5In2.1Al2Zr0.9O12.95 acceptor doping that allows increasing the oxygen-ion-conductivity by a factor of 1.3. Both types of doping lead to increase in the proton conductivity and, as a corollary to this, an increase in the proton concentration. For these phases the degree of hydration depends on the cell parameters, hence, is determined by space availability for OH--groups in the barium coordination. Proton transport dominates in the Ba5In2Al2ZrO13, Ba5In2.1Al2Zr0.9O12.95, and Ba5In1.9Y0.1Al2ZrO13 phases below 600(o)C in humid atmosphere (pH(2)O = 1.92 x 10(-2) atm).

Automated summary

The complex oxide Ba5In1.9Y0.1Al2ZrO13 with hexagonal perovskite structure was successfully synthesized. Protons in the structure are present as energetically different OH--groups involved in hydrogen bonds. Yttrium-doping does not significantly affect the oxygen-ion-conductivity, but acceptor doping increases it by 1.3 times. Both doping types enhance the proton conductivity and concentration. The degree of hydration depends on the cell parameters and the availability of space for OH--groups. Below 600℃ in a humid atmosphere, proton transport dominates in Ba5In2Al2ZrO13, Ba5In2.1Al2Zr0.9O12.95, and Ba5In1.9Y0.1Al2ZrO13 phases.