Temperature-dependent synchrotron XRD study and electrical properties of the (1-x)BZT-(x)BCT lead-free piezoceramics

In recent years, researchers have shown the feasibility of the BZT-xBCT lead-free piezoelectric ceramics for using in various applications such as actuator, energy harvester, high-frequency ultrasonic transducer, etc. However, little evidence of temperature-dependent electrical properties of the BZT-xBCT ceramic was found. Moreover, some researchers have utilized Raman spectroscopy to observe the phase transition of the BZT-xBCT ceramic, but the Raman spectra of ferroelectric polymorphic phases are almost identical and hard to distinguish. In contrast, synchrotron radiation exhibits a high degree of monochromatization and collimation with smaller wavelength than x-ray tubes, resulting in the improvement of resolution for identifying the overlapping peaks. Therefore, this work aims to determine phase coexistence of the BZT-xBCT ceramic near phase boundary region by using highresolution synchrotron x-ray powder diffraction in comparison with the temperature-dependent electrical properties. This work found that the occurrence of thermally-induced polymorphic phase transformations for the BZT-xBCT ceramics plays a significant role in the observed temperature-dependent electrical properties. Moreover, this work observed a trace of surface damaged layer (the presence of low-angle shoulder in the synchrotron XRD profiles) from mechanical grinding during sample preparation for XRD measurement, which has not previously been found in the BZT-xBCT ceramics. These finding will help to better understand the temperaturedependent functional properties of the BZT-xBCT ceramic for transferring into practical applications.