Fundamental workings of chemical substitution at the A-site of perovskite oxides— a ²⁰⁷Pb NMR study of Ba-substituted PbZrO₃

Abstract

Two-dimensional 207Pb solid-state NMR spectroscopy is employed to determine how the substituent chemistry of perovskite oxides can dictate their antiferroelectric (AFE) or ferroelectric (FE) nature. The analysis of (Pb1-xBax)ZrO3 (PBZ)...

Probing Cation Displacements in Antiferroelectrics: A Joint NMR and TEM Approach

“…Both CSA values indicate bonding environments midway between typical covalent and ionic, , which agrees with the off-center Pb atoms forming covalent bonds only with their closest oxygen neighbors. , Based on these comparisons, it is evident that 207 Pb NMR spectroscopy is highly sensitive to Pb–O bonding. The extracted data are consistent with the average structure reported from diffraction studies, and NMR data consistent with our analysis of PZ have previously been reported. − Furthermore, the sharp, well-resolved signals indicate that any structural disorder present in our sample occurs on a much smaller scale than the differences between the two crystallographic sites. ,, While disorder may exist on a local scale, most of the sample is thus well-described by the ordered average structure. This result is in accordance with a previous 207 Pb NMR study which obtained sharp powder line shapes, indicating no random deviations from orthorhombic symmetry and no random Pb displacements in PZ .…”

“…Instead, we can assume that this average is dominated by the shortest bond (in-plane and out-of-plane) present in the structure. 44,59,60 Additionally, Pb 1 −O bonds are known to be more covalent along the ⟨100⟩ direction, 38,39 which is in accordance with the larger CSA for the Pb 1 site. Both CSA values indicate bonding environments midway between typical covalent and ionic, 40,60 which agrees with the off-center Pb atoms forming covalent bonds only with their closest oxygen neighbors.…”

“…Their particular position, shape, and width reflect the differences in Pb–O distances, site symmetry, and deformation of the PbO 12 environments. The characterization of spectral parameters can be significantly improved with advanced pulse sequences such as 2D-PASS, , a technique that also improves spectral resolution in chemically substituted lead-based materials, such as (Pb,Ba)­ZrO 3 …”

“…The characterization of spectral parameters can be significantly improved with advanced pulse sequences such as 2D-PASS, 40,43 a technique that also improves spectral resolution in chemically substituted lead-based materials, such as (Pb,Ba)ZrO 3 . 44 In this work, high-angle annular dark-field (HAADF) and annular bright-field (ABF) STEM imaging techniques were utilized in combination with 207 Pb solid-state NMR spectroscopy to probe the local atomic structure and displacement configurations of the prototype PZ and a modified AFE (Pb 0.97 La 0.02 )(Zr 0.75 Sn 0.14 Ti 0.11 )O 3 (abbreviated PLZST) ceramic. The global structures and properties were characterized via powder X-ray diffraction and polarization-electric field hysteresis measurement, as shown in Figures S1 and S2.…”

Translational Antiphase Boundaries in NaNbO3 Antiferroelectrics

“…(3) Are these interesting entities stable against external electric and thermal fields? So far, most current knowledge of the AFE phenomenon comes from lead-based materials. − As the local structures are of paramount importance for the properties of antiferroelectricity − and form the basis for the future applications of AFE materials, a systematic study of the atomic structures of lead-free AFE compounds like NN is needed.…”