Impact of alternating current electric field poling on coercive field of relaxor ferroelectric crystals

Alternating current (a.c.) electric field poling has been demonstrated to significantly increase the piezoelectricity of relaxor ferroelectric crystals, however, it also reduces coercive electric field (E_C), an important parameter for piezoelectric applications as it determines the maximum driving field of piezoelectric devices. In this work, the impacts of a.c. poling on domain structure and E_C for rhombohedral Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ relaxor ferroelectric crystals are investigated. The results reveal that E_C of [001]-oriented crystal decreases initially and then stabilizes during a.c. poling, nevertheless, E_Cs of [011]-oriented and [111]-oriented crystals maintain relatively stable during a.c. poling process. Based on phase-field simulations and thermodynamic analysis, the variations in E_C are highly associated with the domain structure evolution for different crystal orientations. In [001]-oriented crystal, the gradual elimination of 71° domain walls during a.c. poling leads to a transformation of domain configuration from “4R” to “2R”. In this “2R” domain configuration, the required Gibbs free energy for polarization reversal reduces, accounting for the decreased E_C. In contrast, for [011]-oriented and [111]-oriented crystals, the domain switching processes remain relatively stable with the application of a.c. electric field, therefore keeping E_Cs almost unchanged. This work is expected to benefit the design and application of high-performance ferroelectric materials through the modulation of ferroelectric domain structure.