TY - JOUR
T1 - Discovery of Oxide-Ion Conductors with a New Crystal Structure, BaSc2- x AxSi3O10- x/2 (A = Mg, Ca) by Screening Sc-Containing Oxides through the Bond-Valence Method and Experiments
AU - Niwa, Eiki
AU - Yashima, Masatomo
N1 - Funding Information:
We would like to express special thanks to Dr. K. Fujii and Mr. K. Hibino for helpful discussions. We thank Daiichi Kigenso Kagaku Kogyo Co., Ltd., for the ICP-AES analyses. We would like to also thank to Prof. T. Hashimoto, Dr. H. Kamioka, and Mr. T. Okiba for SEM observations. This study was partly supported by Grants-in-Aid for Scientific Research (KAKEN-HI, Nos. 15H02291, 16H00884, 16H06293, 16H06440, 16H06438, 17K17717, 17H06222) from the Ministry of Education, Culture, Sports, Science and Technology of Japan and JSPS Core-to-Core Program, A. Advanced Research Networks (Solid Oxide Interfaces for Faster Ion Transport).
Publisher Copyright:
© Copyright 2018 American Chemical Society.
PY - 2018/8/27
Y1 - 2018/8/27
N2 - We have discovered oxide-ion conductors with a new crystal structure by combining the bond-valence (BV) method and experiments. In the present work, the BV-based energy barrier Eb for oxide-ion migration was calculated for 123 kinds of Sc-containing oxides as a screening process. We found that the monoclinic BaGd2Si3O10-type barium scandium silicate BaSc2Si3O10 has a relatively low Eb, indicating that it is potentially a new oxide-ion conductor. BaSc2Si3O10 and BaSc1.9A0.1Si3O9.95 (A = Mg, Ca) were prepared by solid-state reactions. Rietveld analyses of X-ray powder diffraction data of these samples were successfully performed using the monoclinic P21/m BaGd2Si3O10-type structure. Lattice volume V of BaSc1.9Mg0.1Si3O9.95 was smaller than V of BaSc2Si3O10 due to the substitution of smaller sized Mg2+ for Sc3+, while the V of BaSc1.9Ca0.1Si3O9.95 was larger than V of BaSc2Si3O10 due to the substitution of larger sized Ca2+ for Sc3+, indicating the formation of solid solutions. Electrical conductivity and ultraviolet-visible (UV-vis) diffuse reflectance measurements indicated that the dominant carrier of BaSc2Si3O10 and BaSc1.9A0.1Si3O9.95 (A = Mg, Ca) was oxide ion. Thus, BaSc2Si3O10 and BaSc1.9A0.1Si3O9.95 (A = Mg, Ca) were found to be new structure-type oxide-ion conductors. These materials are the first examples of pure oxide-ion conductors containing Sc as an essential element. The oxide-ion conductivity of BaSc2Si3O10 was enhanced by doping Mg or Ca owing to the increase in the carrier (oxygen vacancy) concentration. The oxide-ion conductivities of BaSc1.9Mg0.1Si3O9.95 and BaSc1.9Ca0.1Si3O9.95 were approximately 19 times higher than that of BaSc2Si3O10 at 1000 °C. The BV-based energy landscape of BaSc2Si3O10 indicated two- or three-dimensional oxide-ion diffusion along the edges of Si3O10 groups and/or ScO6 octahedra.
AB - We have discovered oxide-ion conductors with a new crystal structure by combining the bond-valence (BV) method and experiments. In the present work, the BV-based energy barrier Eb for oxide-ion migration was calculated for 123 kinds of Sc-containing oxides as a screening process. We found that the monoclinic BaGd2Si3O10-type barium scandium silicate BaSc2Si3O10 has a relatively low Eb, indicating that it is potentially a new oxide-ion conductor. BaSc2Si3O10 and BaSc1.9A0.1Si3O9.95 (A = Mg, Ca) were prepared by solid-state reactions. Rietveld analyses of X-ray powder diffraction data of these samples were successfully performed using the monoclinic P21/m BaGd2Si3O10-type structure. Lattice volume V of BaSc1.9Mg0.1Si3O9.95 was smaller than V of BaSc2Si3O10 due to the substitution of smaller sized Mg2+ for Sc3+, while the V of BaSc1.9Ca0.1Si3O9.95 was larger than V of BaSc2Si3O10 due to the substitution of larger sized Ca2+ for Sc3+, indicating the formation of solid solutions. Electrical conductivity and ultraviolet-visible (UV-vis) diffuse reflectance measurements indicated that the dominant carrier of BaSc2Si3O10 and BaSc1.9A0.1Si3O9.95 (A = Mg, Ca) was oxide ion. Thus, BaSc2Si3O10 and BaSc1.9A0.1Si3O9.95 (A = Mg, Ca) were found to be new structure-type oxide-ion conductors. These materials are the first examples of pure oxide-ion conductors containing Sc as an essential element. The oxide-ion conductivity of BaSc2Si3O10 was enhanced by doping Mg or Ca owing to the increase in the carrier (oxygen vacancy) concentration. The oxide-ion conductivities of BaSc1.9Mg0.1Si3O9.95 and BaSc1.9Ca0.1Si3O9.95 were approximately 19 times higher than that of BaSc2Si3O10 at 1000 °C. The BV-based energy landscape of BaSc2Si3O10 indicated two- or three-dimensional oxide-ion diffusion along the edges of Si3O10 groups and/or ScO6 octahedra.
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U2 - 10.1021/acsaem.8b00701
DO - 10.1021/acsaem.8b00701
M3 - Article
AN - SCOPUS:85064750066
SN - 2574-0962
VL - 1
SP - 4009
EP - 4015
JO - ACS Applied Energy Materials
JF - ACS Applied Energy Materials
IS - 8
ER -