| 研究開始時の研究の概要 |
Spatial domain structures and electric/mechanical field-induced polarization dynamics are deeply studied in order to unravel domain structures and its structural origin, explore atomic polarization distributions and reconstruct the spatial domain patterns, expound polarization dynamic behaviors and analyze the domain switching mechanism, and build physical model and optimize domain configuration.
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| 研究実績の概要 |
Bismuth titanate (BIT) ceramics are potential candidates for high-temperature sensing applications. Despite great advances in performance optimization, the research on domain structures and polarization dynamics are still scarce, limiting further development of such advanced functional materials for more emerging applications. Here, our work focuses on the detailed characterization of domain structures at multi-scale and polarization dynamic behaviors under both electrical and mechanical loads. In brief, the morphologies of domain structures were characterized by PFM at micro-scale, and then structural features of ferroelectric domains were analyzed by TEM and HRTEM at micro-scale and nano-scale, respectively. Most importantly, the polarization vectors of ferroelectric domains were directly observed by atomic-resolution HAADF-STEM. To elaborate the polarization dynamics under electric fields, a series of bias voltages were applied on the surface of ceramics by using PFM lithography, revealing the significant evolution behaviors of ferroelectric domains under applied electric fields. Besides, nanoindentation technique was employed to unravel the ferroelectric domain effect on mechanical properties of BIT ceramics, demonstrating that more domain walls have a positive effect on mechanical hardness. Moreover, polarization dynamics under both constant and cyclic mechanical stresses were elucidated based on nonlinear deformation or domain switching including reversible domain switching and irreversible domain switching in stress-strain curves of ceramics.
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