*2.2. Characterization*

The crystalline structure of BST/0.4BFO-0.6STO film was monitored in the 2*θ* range of 20–60◦ by an X-ray diffractometer (XRD, D8 ADVANCE, Karlsruhe, Germany). During the XRD test, the scanning rate was 0.12 s per step, and the number of scanning steps was a total of 2054 steps. The surface morphology was studied by a tapping mode atomic force microscope (AFM, Bruker Dimension Icon, Santa Barbara, CA, US). The cross-sectional microstructure and EDS spectrum were studied by a field-emission scanning electron microscope (FESEM, ZEISS Gemini300, Oberkochen, Germany) using 2 kV acceleration voltage and 10 kV acceleration voltage, respectively. The polarization electric field (*P-E*) relations were examined by a standard ferroelectric tester (aixACCT TF3000, Aachen, Germany) at room temperature, at a frequency of 10 kHz. In regard to temperaturedependence polarization properties, the loops were measured from –50 to 200 ◦C with a temperature interval of 25 ◦C at 10 kHz. The frequency dependent *P-E* measurements were conducted at room temperature from 500 Hz to 20 kHz. The dielectric properties were characterized by way of an impedance analyzer (HP4294A, Agilent, Palo Alto, CA, USA) at a temperature range of −50 to 250 ◦C from 1 kHz to 100 kHz, with an oscillation voltage of 1.0 V. The temperature-related electrical measurements were carried out with the assistance of a temperature-controlled probe station (Linkam-HFS600E-PB2, London, UK) with a heating rate of 8 ◦C min−1. The cyclic bending tests were realized by using a homebuilt stepper motor control system. The fast energy discharge behavior was evaluated by using a home-built resistance-capacitance (RC) circuit with a load resistance of 100 kΩ.
