Long-Range and Short-Range Structure of Proton-Conducting Y:BaZrO₃

Abstract

Yttrium-doped barium zirconate (BZY) is the most promising candidate for proton-conducting ceramics and has been extensively studied in recent years. The detailed features of the crystal structure, both short-range and long-range, as well as the crystal chemistry driving the doping process, are largely unknown. We use very high resolution X-ray diffraction (HR-XRD) to resolve the crystal structure, which is very slightly tetragonally distorted in BZY, while the local environment around Zr4+ and Y3+ is probed with extended X-ray absorption fine structure (EXAFS), and the symmetry and vibrations are investigated by using Raman spectroscopy. It is found that barium zirconate shows some degree of local deviation from the cubic arystotype even if undoped, which upon substitution by the perceptibly larger Y3+, playing the role of a rigid inclusion, is further increased. This distortion is one limiting factor concerning the Y3+ solubility. The effects are correlated to the proton conduction properties of BZY

Structural, morphological and electrical studies of BaCe0.8Y0.2O3-δ synthesized by solution combustion method

“…Meanwhile, the band appearing at 692 cm is due to vibrational modes involving the dopant ion. However, the unreacted Y 2 O 3 is not detected, which generally appears in the range 725 to 740 cm [22]. During combustion reaction, various gases are evolved due to which new functional groups like carbonates and nitrates may add.…”

Fingerprints of short-range and long-range structure in BaZr1−xHfxO3 solid solutions: an experimental and theoretical study

“…To truly understand the both short and large-range structures, different experimental techniques as well as first principle calculations have been carried out. The results are correlated with two techniques probing the local features of structure and bonding, i.e., X-ray absorption near-edge spectroscopy (EX-AFS) and Raman spectroscopy 26 . These techniques complement x-ray diffraction (XRD) measurements.…”

“…In the case of BZHO the absorptions of Zr K-edge and Hf L III -edge can be obtained by XANES/EXAFS transmission mode, while for Ba L III -edge and Zr L III /L II -edge the TEY methodology is more appropriated to operating condition of National Synchrotron Light Laboratory (LNLS). The X-ray absorption spectroscopy (XAS) has been applied in many case to investigate the local distortions of BZO perovskite 26,30 . On the other hand, Raman spectroscopy is able to investigate the polarizations of both asymmetric and symmetric bonds into the crystal 31 , and first-order vibrational modes can be used to study local distortions 26 .…”

Synchrotron Radiation and Chemistry: Studies of Materials for Renewable Energy Sources

“…Most solid oxide proton conductors have a perovskite structure: despite being reported as an ideal cubic perovskite, the BaZrO 3 proton conductor doped with small amounts of trivalent dopants has been reported as either cubic or tetragonal by different authors, also due to the difficulty in preparing single-phase and homogeneous powders: recently, highresolution XRD allowed to detect a very slight tetragonal distortion upon Y 3+ doping in the otherwise cubic BaZrO 3 perovskite. Site-selective EXAFS on the Y edge also pointed out to significant local symmetry reduction in the dopant environment, that likely induces long-range distortion [41].…”

“…The defect association depends on the particular dopant/host pair, and is generally not easily related to overall electrolyte performance, with Y:BaCeO 3 and Gd:BaCeO 3 displaying significant association, while Y:BaZrO 3 and In:BaCeO 3 do not [54][55][56].…”