@article{9f39736730974b4d8c0e7697a96d1cf1,
title = "In situ poling X-ray diffraction studies of lead-free BiFeO3–SrTiO3 ceramics",
abstract = "The origin of the large electrostrain in BiFeO3-BaTiO3 (BF-BT) ceramics is controversial and has been attributed to either a field-induced transition to a long-range ferroelectric (FE) state or to multi-symmetry, polar nanoregions within a pseudocubic matrix whose vectors approximately align with the direction of the applied field. The (1-x)BiFeO3-xSrTiO3 (BF-xST) solid solution is structurally and microstructurally similar to BF-BT and provides a further case study to assess the origin of electrostrain. In BF-xST, electrostrain is optimized at x = 0.4 (0.15%) which zero field, room temperature full-pattern X-ray diffraction (XRD) Rietveld refinement and scanning/transmission electron microscopy suggest is composed of 15% rhombohedral (R) cores, surrounded by 85% pseudocubic (PC) shells. In-situ poling synchrotron XRD reveals that all peaks remain singlet and exhibit no change in full width half maximum up to 100 kV cm−1, confirming the absence of long-range FE order and the retention of short-range polar order, despite the large applied field. Strain anisotropy (calculated from individual peaks) of ε220 > ε111 > ε200 and the associated strain orientation distribution however, indicate the existence of local orthorhombic (O), R and tetragonal (T) symmetries. The data therefore imply the existence under poling of multi-symmetry polar nanoregions in BF-0.4ST rather than a long FE phase, supporting the model described by Wang and co-workers (2019) for BF-BT compositions.",
keywords = "BF-ST, Electroceramics, In-situ poling synchrotron XRD, Strain",
author = "Zhilun Lu and Ge Wang and Linhao Li and Yuhe Huang and Antonio Feteira and Weichao Bao and Kleppe, {Annette K.} and Fangfang Xu and Dawei Wang and Reaney, {Ian M.}",
note = "Funding Information: We wish to acknowledge the Henry Royce Institute for Advanced Materials , funded through EPSRC grants EP /R00661X/1, EP /S019367/1, EP /P02470X/1 and EP /P025285/1, for the financial support at The University of Sheffield , and thank the EPSRC for funding (Substitution and Sustainability in Functional Materials and Devices, EP /L017563/1, SYnthesizing 3D METAmaterials for RF, microwave and THz applications (SYMETA), EP /N010493/1, FPeT: Framework for designing piezoelectric transformer power supplies, EP /P015859/1), and Diamond Light Source for access to beamline I15 (proposal number CY21714-3) that contributed to the results presented here. Additionally, we thank Tim. P. Comyn (Ionix Advanced Technologies) and David. A. Hall ( University of Manchester ) for assistance with sample preparation, and support provided by Functional Materials and Devices group from The University of Sheffield . Funding Information: The origin of the large electrostrain in BiFeO3-BaTiO3 (BF-BT) ceramics is controversial and has been attributed to either a field-induced transition to a long-range ferroelectric (FE) state or to multi-symmetry, polar nanoregions within a pseudocubic matrix whose vectors approximately align with the direction of the applied field. The (1-x)BiFeO3-xSrTiO3 (BF-xST) solid solution is structurally and microstructurally similar to BF-BT and provides a further case study to assess the origin of electrostrain. In BF-xST, electrostrain is optimized at x = 0.4 (0.15%) which zero field, room temperature full-pattern X-ray diffraction (XRD) Rietveld refinement and scanning/transmission electron microscopy suggest is composed of 15% rhombohedral (R) cores, surrounded by 85% pseudocubic (PC) shells. In-situ poling synchrotron XRD reveals that all peaks remain singlet and exhibit no change in full width half maximum up to 100 kV cm?1, confirming the absence of long-range FE order and the retention of short-range polar order, despite the large applied field. Strain anisotropy (calculated from individual peaks) of ?220 > ?111 > ?200 and the associated strain orientation distribution however, indicate the existence of local orthorhombic (O), R and tetragonal (T) symmetries. The data therefore imply the existence under poling of multi-symmetry polar nanoregions in BF-0.4ST rather than a long FE phase, supporting the model described by Wang and co-workers (2019) for BF-BT compositions.We wish to acknowledge the Henry Royce Institute for Advanced Materials, funded through EPSRC grants EP/R00661X/1, EP/S019367/1, EP/P02470X/1 and EP/P025285/1, for the financial support at The University of Sheffield, and thank the EPSRC for funding (Substitution and Sustainability in Functional Materials and Devices, EP/L017563/1, SYnthesizing 3D METAmaterials for RF, microwave and THz applications (SYMETA), EP/N010493/1, FPeT: Framework for designing piezoelectric transformer power supplies, EP/P015859/1), and Diamond Light Source for access to beamline I15 (proposal number CY21714-3) that contributed to the results presented here. Additionally, we thank Tim. P. Comyn (Ionix Advanced Technologies) and David. A. Hall (University of Manchester) for assistance with sample preparation, and support provided by Functional Materials and Devices group from The University of Sheffield. Publisher Copyright: {\textcopyright} 2021 The Author(s)",
year = "2021",
month = may,
day = "8",
doi = "10.1016/j.mtphys.2021.100426",
language = "English",
volume = "19",
journal = "Materials Today Physics",
issn = "2542-5293",
publisher = "Elsevier BV",
}