The stability of the polarization state in Na_(0.5)Bi_(0.5)TiO_(3)(NBT)ceramics has been a long-standing problem for its use in piezoelectric applications at elevated temperatures.It has been generally believed that t...The stability of the polarization state in Na_(0.5)Bi_(0.5)TiO_(3)(NBT)ceramics has been a long-standing problem for its use in piezoelectric applications at elevated temperatures.It has been generally believed that the polarization state,depolarization temperature,and depolarization process are all linked to the grain size in these materials.In this work,we perform a thorough Piezoresponse Force Microscopy(PFM)study of the NBT ceramic samples with substantially different grain sizes sintered as a function of temperature.As-grown,macroscopically poled,and locally poled samples were investigated focusing on the polarization behavior at depolarization temperature.Switching Spectroscopy PFM(SS-PFM)measurements were conducted as a function of grain size and temperature.No direct correlation is observed between the grain size and the switching parameters in any sample.However,temperature-dependent measurements reveal significant differences that are explained by different concentrations of oxygen vacancies.We rationalized the observed behavior,e.g.apparent stabilization of the locally probed polarization above the depolarization temperature,by accumulation and depletion of oxygen vacancies in the vicinity of the internal boundary of the poled region.Significant asymmetry of the PFM hysteresis loops at elevated temperatures confirms this assumption.展开更多
基金funded by the German Research Foundation DFG within the framework of the project“Tuning the electrocaloric efficiency in lead-free ceramics”(DFG Project SH 709/4-1(project number 448662623))the European Union HORIZON-WIDERA-2023-TALENTS-01 program within the framework of the project“Low-dimensional ferroelectrics for advanced electronic and biomedical devices”(FeLow-D)(Grant agreement number 101186499)+1 种基金the scope of the project CICECO-Aveiro Institute of Materials,UIDB/50011/2020,UIDP/50011/2020&LA/P/0006/2020,financed by national funds through the FCT/MECPartial support through the Horizon MSCA project“Piezo2D”(GA#101131229)is acknowledged.
文摘The stability of the polarization state in Na_(0.5)Bi_(0.5)TiO_(3)(NBT)ceramics has been a long-standing problem for its use in piezoelectric applications at elevated temperatures.It has been generally believed that the polarization state,depolarization temperature,and depolarization process are all linked to the grain size in these materials.In this work,we perform a thorough Piezoresponse Force Microscopy(PFM)study of the NBT ceramic samples with substantially different grain sizes sintered as a function of temperature.As-grown,macroscopically poled,and locally poled samples were investigated focusing on the polarization behavior at depolarization temperature.Switching Spectroscopy PFM(SS-PFM)measurements were conducted as a function of grain size and temperature.No direct correlation is observed between the grain size and the switching parameters in any sample.However,temperature-dependent measurements reveal significant differences that are explained by different concentrations of oxygen vacancies.We rationalized the observed behavior,e.g.apparent stabilization of the locally probed polarization above the depolarization temperature,by accumulation and depletion of oxygen vacancies in the vicinity of the internal boundary of the poled region.Significant asymmetry of the PFM hysteresis loops at elevated temperatures confirms this assumption.
