Local structure around Yb in SrZr_1-xYb_xO₃

Abstract

Local structures around Yb ions in the proton conductor Yb-doped SrZrO3 have been investigated at room temperature by the EXAFS (extended x-ray absorption fine structure) technique. The radial structure functions from the Zr K edge in SrZrO3, SrZr0.95Yb0.05O3 and SrZr0.9Yb0.1O3 and the Yb LIII edge in Yb2O3 show clear contributions by next-nearest ions at 3.0-4.0 Å, while those from the Yb LIII edge in SrZr0.95Yb0.05O3 and SrZr0.9Yb0.1O3 are mainly constructed by a first-nearest signal. Moreover, the nearest Yb-O distributions at 1.0-2.0 Å have a side peak with a strong intensity in both SrZr0.95Yb0.05O3 and SrZr0.9Yb0.1O3. It is shown from the analyses of the side peak that the nearest Yb-O bonds consist of two distances (1.96 and 2.18 Å). Two structural models around the Yb ion have been suggested and discussed from these results.

Short-Range Structure of Proton-Conducting Perovskite BaInxZr1-xO3-x/2 (x = 0−0.75)

“…It is, therefore, quite surprising that there are only a few experimental reports on the short-range structure of proton-conducting perovskites. To our knowledge, these investigations, which indeed have provided some important information, are limited to X-ray absorption fine structure (XAFS) investigations of doped perovskites based on SrCeO 3 , SrZrO 3 , BaCeO 3 , – and CaZrO 3 . , However, no investigations have focused on the effect of dopant level and the role of oxygen vacancies on the short-range structure and its direct relationship to the proton conductivity. To understand the details of the proton transport in hydrated perovskites, a thorough knowledge about the short-range structure is essential.…”

Local Environment of Yttrium in Y-Doped Barium Cerate Compounds

“…It is rather surprising that, in comparison with the several theoretical studies, only a very limited number of papers are dedicated to the study of the local structure of proton conducting perovskites by experimental methods. In particular, just a few XAFS (X-ray absorption fine structure) studies concern Yb:SrCeO 3 , Yb:SrZrO 3 , lanthanide-doped CaZrO 3 , , and Ce-, Nd-, and U-doped calcium titanate; concerning barium cerate, only one partial account exists in the literature about an XAFS experiment on BaCe 1- x Y x O 3- δ , while a very recent paper investigates dopant partitioning over Ba and Ce sites in Gd- and Yb-doped barium cerate …”

Dielectric relaxation in Yb-doped SrZrO3

“…Experimentally, the enhancement factor for the off-centred Bi dipoles was also reported to be 20 or more in Sr 1−1.5x Bi x TiO 3 [28]. Since the off-centred Yb was suggested by EXAFS measurement in SrZrO 3 :Yb [7], the effective dipole moment for Yb-OH can be considered to have such a large value p eff = 20 p Yb−OH from the present calculation. The attractive energy (φ < 0) for Yb-clustering is evaluated at about −85 meV, as shown in figure 7.…”

“…Regarding the local structure around the dopant ions, it was found in EXAFS measurements for SrZrO 3 :Yb that the nearest Yb-O bonds consisted of two large different distances (1.96 and 2.18 Å) [7]. This result implied that the Yb dopants were displaced about 0.1 Å from the central position of the [YbO 6 ]-octahedron [7].…”

“…Regarding the local structure around the dopant ions, it was found in EXAFS measurements for SrZrO 3 :Yb that the nearest Yb-O bonds consisted of two large different distances (1.96 and 2.18 Å) [7]. This result implied that the Yb dopants were displaced about 0.1 Å from the central position of the [YbO 6 ]-octahedron [7]. Since undoped-SrZrO 3 belongs to the space group Pnma (Z = 4, orthorhombic) below ∼1000 K [8,9], the Zr ions locate at the centre of the [ZrO 6 ]-octahedron.…”