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New Structure Family of Oxide-ion Conductors Based on BaGdInO4

Abstract

BaRInO4-based materials (R = Nd, Sm, Ho, Y, Er and Yb) have attracted much attention due to their oxide-ion conduction and unique (110) layered perovskite structures (monoclinic P21/c BaNdInO4-type structure). Here, we report new compounds BaGdInO4 and BaGd0.9A0.1InO3.95 (A = Mg, Ca and Sr). It was found that these compounds belong to a new structure family of oxide-ion conductors. Surprisingly, the single-crystal and powder X-ray diffraction analyses have shown that the crystal structures of BaGdInO4 and BaGd0.9A0.1InO3.95 (A = Mg, Ca, Sr) are quite different from those of the monoclinic BaRInO4-based materials. We found that BaGdInO4 and BaGd0.9A0.1InO3.95 (A = Mg, Ca, Sr) have an orthorhombic Pnma Ba2Y2CuPtO8-type structure consisting of InO5 square pyramid, InO6 octahedron, (Gd,A)O7 polyhedron (monocapped trigonal prism) and Ba cation where Gd,A denotes Gd or Gd0.9A0.1. Four edge-sharing (Gd,A)O7 polyhedra build up an infinite one-dimensional ((Gd,A)4O20) chain. Oxide-ion conduction was confirmed for BaGdInO4 and BaGd0.9Ca0.1InO3.95 by the electrical conductivity measurements at different oxygen partial pressures P(O2). The oxide-ion conductivity of BaGd0.9Ca0.1InO3.95 was 381 times higher than that of BaGdInO4 at 400 oC, which was attributed to the higher oxygen vacancy concentration in BaGd0.9Ca0.1InO3.95. The oxide-ion conductivity of BaGd0.9Ca0.1InO3.95 was comparable to those of monoclinic BaNdInO4-type BaRInO4-based materials. The bulk conductivity of BaGd0.9Ca0.1InO3.95 was 1.3 × 10−3 S cm−1 at 700 oC and P(O2) = 10−4 atm in the electrolyte domain. The bond valence-based energy landscapes of BaGd0.9Ca0.1InO3.95 and BaGdInO4 indicated one-dimensional oxide-ion migration pathways on the faces of (Gd,Ca)O7 polyhedra along the ((Gd,Ca) 4O20) chain in the b direction. The discovery and unique features of the orthorhombic BaGdInO4-based materials might develop materials chemistry of oxide-ion conductors.

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Supplementary files

Article information


Submitted
14 Dec 2019
Accepted
15 Mar 2020
First published
16 Mar 2020

J. Mater. Chem. A, 2020, Accepted Manuscript
Article type
Paper

New Structure Family of Oxide-ion Conductors Based on BaGdInO4

H. Yaguchi, K. Fujii and M. Yashima, J. Mater. Chem. A, 2020, Accepted Manuscript , DOI: 10.1039/C9TA13704A

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