Optimizing High-Power Performance of [001]-Oriented Pb(Mg_1/3Nb_2/3)-PbTiO₃ Through Combined DC and AC Polarization Above Curie Temperature

Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ single crystals (PMN-PT SCs) are widely utilized in high-performance piezoelectric devices due to their exceptional piezoelectric properties. Among the various post-processing techniques for domain engineering in PMN-PT SCs, alternating current polarization (ACP) has become a widely adopted method for enhancing piezoelectric performance. This study proposes a new ultrahigh-temperature field-cooling polarization (UFCP) technique, combining direct current polarization (DCP) and ACP with field cooling above the Curie temperature. Dielectric spectra indicate that the UFCP method promotes electric field-induced phase transitions above the Curie point, forming a stable multiphase configuration. The transverse piezoelectric coefficient <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>d</mi></mrow><mrow><mn>31</mn></mrow></msub></mrow></semantics></math></inline-formula> of UFCP SCs is <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1126</mn><mtext> </mtext><mi mathvariant="normal">p</mi><mi mathvariant="normal">C</mi><mo>/</mo><mi mathvariant="normal">N</mi></mrow></semantics></math></inline-formula>, and the electromechanical coupling factor <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>k</mi></mrow><mrow><mn>31</mn></mrow></msub></mrow></semantics></math></inline-formula> is 0.559. Compared with traditional DCP, UFCP increases <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>d</mi></mrow><mrow><mn>31</mn></mrow></msub></mrow></semantics></math></inline-formula> by 68.6%, the mechanical quality factor <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>Q</mi></mrow><mrow><mi>m</mi></mrow></msub></mrow></semantics></math></inline-formula> by 16.7%, and the piezoelectric figure of merit (FOM) by 98.3%. Furthermore, under high-power excitation with a root-mean-square voltage of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>15</mn><mtext> </mtext><mi mathvariant="normal">V</mi></mrow></semantics></math></inline-formula>, UFCP achieves a 343% increase in power and a 130.5% improvement in the FOM compared with DCP, demonstrating its potential for enhancing high-power performance in practical applications.