No abstract

The oxide-ion conductivity of NdBaInO 4 has been increased by Sr doping. Nd 0.9 Sr 0.1 BaInO 3.95 showed the highest electrical conductivity among Nd 1Àx Sr x BaInO 4Àx/2 (x ¼ 0.0, 0.1, 0.2, and 0.3). The oxide-ion conductivity s ion of Nd 0.9 Sr 0.1 BaInO 3.95 (s ion ¼ 7.7 Â 10 À4 S cm À1 ) is about 20 times higher than that of NdBaInO 4 (s ion ¼ 3.6 Â 10 À5 S cm À1 ) at 858 C, and the activation energy of oxide-ion conduction is a little lower for Nd 0.9 Sr 0.1 BaInO 3.95 (0.795(10) eV) than that for NdBaInO 4 (0.91(4) eV). The structure analysis based on neutron powder diffraction data revealed that the Sr exists at the Nd site and oxygen vacancies are observed in Nd 0.9 Sr 0.1 BaInO 3.95 . This result indicates that the increase of the oxide-ion conductivity is mainly due to the increase of the carrier concentration. The bond valence-based energy landscape indicated two-dimensional oxide-ion diffusion in the (Nd,Sr) 2 O 3 unit on the bc-plane and a decrease of the energy barrier by the substitution of Nd with Sr cations. † Electronic supplementary information (ESI) available: A document containing the crystallographic data of Nd 0.9 Sr 0.1 BaInO 3.95 , additional experimental information, and a crystallographic information le (CIF) of Nd 0.9 Sr 0.1 BaInO 3.95 . See

BaNdInO 4 is a new structure family of oxide-ion conductors. In the present work, we have investigated the crystal structure and electrical conductivity of Ba 1+x Nd 1−x InO 4−x/2 where x is the excess Ba content. It was found that Ba 1.1 Nd 0.9 InO 3.95 shows (i) about 12 times higher oxide-ion conductivity at 858 • C and (ii) a little lower activation energy for oxide-ion conduction than BaNdInO 4 . The higher oxide-ion conductivity of Ba 1.1 Nd 0.9 InO 3.95 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 Ba 1.1 Nd 0.9 InO 3.95 . The refined occupancy factor of oxygen atom 0.9829( 17) indicates the higher concentration of oxygen vacancies in Ba 1.1 Nd 0.9 InO 3.95 , compared with BaNdInO 4 , giving higher oxide-ion conductivity in Ba 1.1 Nd 0.9 InO 3.95 . 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 Ba 1.1 Nd 0.9 InO 3.95 at 800 and 24 • C indicated two-dimensional oxide-ion diffusion in the A rare earth oxide (Nd,Ba) 2 O 3 unit on the bc plane.