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Discovery of a new crystal structure family of oxide-ion conductors

Oxide-ion conducting ceramic materials have received considerable attention because of their potential applications in solid oxide fuel cells, oxygen separation membranes, and gas sensors.

Currently, most research about oxide-ion conducting ceramics is limited to materials with specific structure-types, such as fluorites, perovskites, K₂NiF₄, mellilites, and apatites. However, it is necessary to investigate new structure-type ceramics for the further development of oxide-ion conductors.

Recently, a research group led by Masatomo Yashima and Kotaro Fujii of Tokyo Institute of Technology discovered the new crystal structure family of oxide-ion conductors of NdBaInO4 using a concept of structure design based on ionic size.

NdBaInO4 was synthesized by a solid-state reaction and the crystal structure was determined from synchrotron and neutron powder diffraction data.

The crystal structure analysis revealed that NdBaInO4 belongs to a completely new structure family. The oxide-ion conduction was confirmed by electrical conductivity measurements. Furthermore, the research group succeeded in improving the oxide-ion conductivity by about 20 times by Sr doping at Nd sites that yielded the composition of Nd_0.9S_r0.1BaIn_O3.95.

The discovery of this new material of NdBaInO4 is expected to lead to the development of new ionic conductors for better solid oxide fuel cells, oxygen concentrators, and electronic materials.