Crystal Structure and Oxide-Ion Conductivity of Ba1+xNd1-xInO4-x/2

BaNdInO4 is a new structure family of oxide-ion conductors. In the present work, we have investigated the crystal structure and electrical conductivity of Ba1+xNd1-xInO4-x/2 where x is the excess Ba content. It was found that Ba1.1Nd0.9InO3.95 shows (i) about 12 times higher oxide-ion conductivity at 858 degrees C and (ii) a little lower activation energy for oxide-ion conduction than BaNdInO4. The higher oxide-ion conductivity of Ba1.1Nd0.9InO3.95 is mainly ascribed to higher carrier concentration. Careful structure analyses using both the single-crystal X-ray diffraction and time-of-flight (TOF) neutron powder diffraction data enabled to determine the position of excess Ba cation and occupancy factor of O anion. It was found that the excess Ba cation substitutes for Nd cation and that oxygen vacancies exist in Ba1.1Nd0.9InO3.95. The refined occupancy factor of oxygen atom 0.9829(17) indicates the higher concentration of oxygen vacancies in Ba1.1Nd0.9InO3.95, compared with BaNdInO4, giving higher oxide-ion conductivity in Ba1.1Nd0.9InO3.95. The larger-sized Ba substitution for Nd cation makes the bottleneck size larger, leading to the lower activation energy. The bond valence-based energy landscape calculated for the refined crystal structure of Ba1.1Nd0.9InO3.95 at 800 and 24 degrees C indicated two-dimensional oxide-ion diffusion in the A rare earth oxide (Nd, Ba)(2)O-3 unit on the bc plane. (c) 2017 The Electrochemical Society. All rights reserved.