Probing local structure of pyrochlore lead zinc niobate with synchrotron x-ray absorption spectroscopy technique

Abstract

Local structure of lead zinc niobate (PZN) ceramic, synthesized via B-site oxide precursor route in atmospheric pressure, was investigated using synchrotron x-ray absorption spectroscopy (XAS) technique. The x-ray absorption near-edge structure (XANES) simulation was first carried out. The XANES simulation results indicate that the PZN ceramic is in pyrochlore phase having Zn 2þ substituted on Nb 5þ site. Afterwards, the extended x-ray absorption fine structure (EXAFS) analysis was performed to extract the bond length information between Zn 2þ and its neighboring atoms. From the EXAFS fitting, the bond length between Zn 2þ and Pb 2þ in the pyrochlore phase was found to be longer than the previously reported bond length in the perovskite phase. Further, with the radial distribution information of Zn 2þ 's neighboring atoms, the formation energies along the precursor-to-pyrochlore and precursor-to-perovskite reaction paths were calculated using the density functional theory (DFT). The calculated results show that the formation energy of the perovskite phase is noticeably higher than that of the pyrochlore phase, which is influenced by the presence of energetic Pb 2þ lone pair, as the perovskite phase has shorter Zn 2þ to Pb 2þ bonding. This therefore suggests the steric hindrance of Pb 2þ lone pair and the mutual interactions between Pb 2þ lone pair and Zn 2þ are main causes of the instability of lead zinc niobate in the perovskite structure and confirm the efficacy of XAS and DFT analysis in revealing local structural details of complex pyrochlore materials. V C 2013 AIP Publishing LLC. [http://dx.

Advances in Understanding Mechanisms of Perovskites and Pyrochlores as Electrocatalysts using In‐Situ X‐ray Absorption Spectroscopy

“…shown in Figure 2 d. [36] Accordingly, the distances of the Pb À Zn and PbÀNb bonds in the pyrochlore oxide were determined as 3.8442 and 3.4413 , respectively, longer than in perovskite phases. [37] In other words, ex-situ XAS is a powerful technique for understanding the intrinsic properties of materials.…”

“…Indeed, EXAFS spectra clearly show the structural properties of materials including the distance between neighboring atoms, environments of local, short‐range, and long‐range coordination, and other things . For instance, the geometric local structure of Pb 1.83 Zn 0.29 Nb 1.71 O 6.39 pyrochlore can clearly be obtained, as shown in Figure d . Accordingly, the distances of the Pb−Zn and Pb−Nb bonds in the pyrochlore oxide were determined as 3.8442 and 3.4413 Å, respectively, longer than in perovskite phases .…”

X-ray absorption spectroscopy and density functional analysis of the Fe3+ distribution profile on Al sites in a chrysoberyl crystal, BeAl2O4:Fe3+

“…To determine the distribution of the Fe substituting on both Al sites, the ratio of the main peaks was investigated. The absolute and the relative positions of the peaks can be used to interpret which calculated spectrum is the closest to the experimental spectrum (Kanchiang et al, 2013). However, since the XANES calculation can never exactly reproduce an experimental spectrum, pertinent criteria have to be chosen in order to determine the suitable proportions of Fe 3+ in the two crystallographic sites (Mottana et al, 1999).…”

Advances in Understanding Mechanisms of Perovskites and Pyrochlores as Electrocatalysts using In‐Situ X‐ray Absorption Spectroscopy

“…Copyright 2012 Nature Publishing Group. Angewandte Chemie shown in Figure 2 d. [36] Accordingly, the distances of the Pb À Zn and PbÀNb bonds in the pyrochlore oxide were determined as 3.8442 and 3.4413 , respectively, longer than in perovskite phases. [37] In other words, ex-situ XAS is a powerful technique for understanding the intrinsic properties of materials.…”