1：Experimental Design and Method Selection:

The study involved applying an alternating current electric field on pre-direct current poled (DCP) single crystals to investigate the induced dielectric and piezoelectric properties. The ACT conditions were optimized at 1 kV/mm, 50 Hz over 20 cycles.

2：Sample Selection and Data Sources:

[001]-oriented 0.25PIN-0.43PMN-0.32PT single crystals near the morphotropic phase boundary were used. The samples were cut into 5 × 5 × 0.5 mm3 and annealed at 600 °C for 10 h to release residual stress.

3：25PIN-43PMN-32PT single crystals near the morphotropic phase boundary were used. The samples were cut into 5 × 5 × 5 mm3 and annealed at 600 °C for 10 h to release residual stress. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: High voltage amplifier (PZD2000A, Trek), functional generator (DG1022, RIGOL), oscilloscope (DS1104Z, RIGOL), quasistatic d33 meter (ZJ-2, CAS), LCR meter (E4284A, Agilent), high temperature chamber.

4：Experimental Procedures and Operational Workflow:

The single crystal samples were first poled under a direct current electric field of 1 kV/mm at room temperature for 5 min. Then, an alternating current electric field was applied under various conditions of frequency, cycles, and amplitude. The piezoelectric constant d33 and dielectric permittivity were measured at room temperature, and the temperature dependence of dielectric permittivity and dielectric loss was measured from room temperature to 300 °C.

5：Data Analysis Methods:

The dielectric permittivity was calculated from the capacitance measured by the LCR meter. The piezoelectric coefficient was measured using the quasistatic d33 meter. The temperature dependence of dielectric properties was analyzed to understand the phase transition behavior.