Effect of chemical state and occupation site of RE (RE = Yb, Y, Eu, Sm, Nd) on crystal structure and optical property of BaCe1-xRExO3-δ —Analyses of origin of peculiar crystal structure and property of BaCe1-xNdxO3-δ. (March 2017)

• Record Type: Journal Article
• Authors: Niwa, Eiki; Hosaka, Tomomi; Onoe, Takahiro; Shimizu, Misa; Hatakeyama, Yoshikiyo; Judai, Ken; Fujishiro, Fumito; Hashimoto, Takuya
• Is Part Of: Materials research bulletin. Volume 87(2017)
• Page Start: 6
• Page End: 13
• Publication Date: 2017-03
• Subjects: A. Oxide -- B. Optical property -- C. X-ray diffraction -- D. Crystal structure -- D. Defect; Materials -- Periodicals; Crystal growth -- Periodicals; Matériaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Crystal growth; Materials; Periodicals; 620.11
• DOI: 10.1016/j.materresbull.2016.11.005
• Languages: English
• ISSNs: 0025-5408

Abstract

Graphical abstract: Highlights: Crystal structures of various BaCe1- x RE x O3- δ (RE: rare earth) have been clarified. The structure varies by RE 3+ substitution involving increase of δ except for RE = Nd. The unique crystal structure and thermal expansion were observed for BaCe1- x Nd x O3- δ . Existence of Nd 4+ can be an origin of the unique crystal structure and property. Partial Nd 3+ mixing for Ba-site in BaCe1- x Nd x O3- δ was proposed by optical spectra. Abstract: Crystal structure, temperature dependence of molar volume and optical property of single phase BaCe1- x RE x O3- δ were investigated. The crystal structure of BaCe1- x RE x O3- δ (RE; Yb, Y, Eu, and Sm) and BaCe1- x Nd x O3- δ changes from primitive orthorhombic to monoclinic and body-centered orthorhombic, respectively, by increasing x . Almost linear relationship between ionic radius of RE 3+ and the molar volume are observed for BaCe1- x RE x O3- δ with RE of Yb, Y, Eu, Sm; however, that of BaCe1- x Nd x O3- δ is smaller than the relationship. As one of the origins, proposed is that Nd in BaCe1- x Nd x O3- δ is near 4+, showing agreement with reported oxygen nonstoichiometry, in-situ X-ray absorption spectra and reduction expansion observed in this work. As another origin, partial Ba-site mixing of Nd 3+ is proposed from separation of BaCO3 from BaCe0.9 Nd0.1 O3- δ by high temperature sintering. The lower optical band gap of BaCe0.9 Nd0.1 O3- δ observed by reflectance spectroscopy, can also be explained by the partial mixing.