The crystal structures and electrical properties of lead-free BiFeO3-BaTiO3 [(1-x)BFxBT] piezoelectric system are investigated as a function of BaTiO3 concentration. The well-saturated P-E hysteresis loop was observed in the 0.80BiFeO3–0.20BaTiO3 composition system, while a less hysteretic strain-electric field curve was exhibited by the 0.70BiFeO3–0.30BaTiO3 with a strain hysteresis of 16%, the value comparable to PZT-based piezoelectric ceramics. The crystal structures investigated under the synchrotron radiation X-ray diffraction exhibited a rhombohedral structure for BFBT system with x = 0.10–0.25 and a pseudo-cubic structure for BFBT system with x = 0.30–0.40. The structural phase diagram for the BiFeO3-BaTiO3 system is suggested based on the results of temperature-dependent synchrotron radiation X-ray diffraction measurement and investigated electrical properties.

The electric field-dependent crystal structures and electrical properties were investigated in the 0.67BiFeO 3 0.33BaTiO 3 (BF33BT) lead-free piezoelectric ceramics. The room temperature synchrotron radiation X-ray diffraction (SR-XRD) patterns measured, without the application of an electric field, revealed all the peaks to be single suggesting the cubic like crystal structure of the BF33BT system. The domain switching was ascertained in the PE hysteresis loop and SE curve meanwhile, SR-XRD patterns exhibited beyond doubt single peak. In order to study the electric field induced structural phase transition, SR-XRD was measured in BF33BT ceramics as a function of electric field. The electric field applied up to 40 kV/cm with bipolar cycling was parallel along the longitudinal lattice response direction that was similar for the piezoelectric response measuring method. The shift of SR-XRD peaks to lower and/or higher angle in comparison to the peak position of zero field-SR-XRD was found to depend on the direction and intensity of the applied electric field. The peak shape under maximum electric field was quite same that of SR-XRD patterns at zero electric field. Importantly, the single peak shape was maintained for all the SR-XRD measured under the electric field. Therefore, the electric field induced structural phase transition did not occur in the BF33BT ceramics.

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