Fundamental workings of chemical substitution at the A-site of perovskite oxides: a 207Pb NMR study of Ba-substituted PbZrO3
EGERT S. 2, KORUZA J. 3, BREITZKE H. 2, ZHAO C. 2, MALI? B. 4, BUNTKOWSKY G. 2, GROSZEWICZ P. 1
1 TU Delft, Delft, Netherlands; 2 TU Darmstadt, Darmstadt, Germany; 3 TU Graz, Graz, Austria; 4 Jožef Stefan Institute, Ljubljana, Slovenia
Lead zirconate (PbZrO3, PZ) is a prototype antiferroelectric material from which state-of-the-art functional energy storage ceramics are derived by chemical substitution. A thorough understanding of the structure-property relations in PZ-based materials is essential for performance improvement and the design of more environmentally friendly replacements. (Pb1−xBax)ZrO3 (PBZ) can serve as a model system for studying the effect of A-site substitution in the perovskite lattice, with barium destabilizing the antiferroelectric state.
Two-dimensional 207Pb solid-state NMR spectra of PZ and of two compositions of PBZ were recorded to analyze the effect of barium substitution on the local structure. Upon crossing a threshold value for x, barium induces a macroscopic phase transition into a FE state (x=12). 207Pb NMR demonstrates the introduction of Ba2+ ions to PZ causes local-scale lattice expansions in their vicinity, resulting in the collapse of two lead sites into one. The stabilization of the larger volume site favors shorter shortest Pb-O distances and reflects a tendency for larger Pb2+ displacements. This is indication of a more covalent bonding environment, which may originate from the lower polarizability of Ba2+, facilitating the formation of stronger Pb-O bonds in their vicinity.
From the local structural point of view, we propose the substitution-induced AFE→FE phase transition is therefore related to an increasing correlation of larger lead displacements in larger oxygen cavities as the content of barium increases. These results prove 207Pb NMR spectroscopy as a capable method to characterize structure-property relations in PbZrO3-based antiferroelectric and ferroelectric ceramics.
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