Symmetry-mode analysis for intuitive observation of structure–property relationships in the lead-free antiferroelectric (1− x) AgNbO3–xLiTaO3
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Date
2019-06-21
Journal Title
Journal ISSN
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Publisher
International Union of Crystallography
Abstract
Functional materials are of critical importance to electronic and smart devices. A deep understanding of the structure–property relationship is essential for designing new materials. In this work, instead of utilizing conventional atomic coordinates, a symmetry-mode approach is successfully used to conduct structure refinement of the neutron powder diffraction data of (1−x)AgNbO3–xLiTaO3 (0 ≤ x ≤ 0.09) ceramics. This provides rich structural information that not only clarifies the controversial symmetry assigned to pure AgNbO3 but also explains well the detailed structural evolution of (1−x)AgNbO3–xLiTaO3 (0 ≤ x ≤ 0.09) ceramics, and builds a comprehensive and straightforward relationship between structural distortion and electrical properties. It is concluded that there are four relatively large-amplitude major modes that dominate the distorted Pmc21 structure of pure AgNbO3, namely a Λ3 antiferroelectric mode, a T4+ a−a−c0 octahedral tilting mode, an H2 a0a0c+/a0a0c− octahedral tilting mode and a Γ4− ferroelectric mode. The H2 and Λ3 modes become progressively inactive with increasing x and their destabilization is the driving force behind the composition-driven phase transition between the Pmc21 and R3c phases. This structural variation is consistent with the trend observed in the measured temperature-dependent dielectric properties and polarization–electric field (P-E) hysteresis loops. The mode crystallography applied in this study provides a strategy for optimizing related properties by tuning the amplitudes of the corresponding modes in these novel AgNbO3-based (anti)ferroelectric materials. © International Union of Crystallography - Open Access
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Keywords
Neutron diffraction, Ceramics, Electrical properties, Antiferroelectric materials, Phase transformations, Crystallography
Citation
Lu, T., Tian, Y., Studer, A., Narayanan, N., Li, Q., Withers, R., Jin, L., Mendez-Gonzalez, Y., Pelaiz-Barranco, A., Yu, D., McIntyre, G. J., Xu, Z., Wei, X., Yan, H. & Liu, Y. (2019). Symmetry-mode analysis for intuitive observation of structure–property relationships in the lead-free antiferroelectric (1− x) AgNbO3–xLiTaO3. IUCrJ, 6(4), 740-750. doi:10.1107/S2052252519007711