Antiferroelectric materials, owing to their electric-field-induced reversible antiferroelectric–ferroelectric phase transition, have broad application prospects in pulsed power systems, electric vehicles, displacement sensors, shape memory devices, etc.

The dipole configurations of antiferroelectric systems, represented by PbZrO₃, have been extensively studied. However, in Pb(B′_1/2B′′_1/2)O₃-type perovskite oxides with more complex structure, the competing interaction mechanisms arising from the ordered arrangement of B-site complex cations remain unclear, hindering the rational design of high-performance complex antiferroelectric systems.

In a study published in Advanced Functional Materials, researchers from the Xinjiang Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences (CAS), along with collaborators from the Shanghai Institute of Ceramics of CAS, Fujian Institute of Research on the Structure of Matter of CAS, City University of Hong Kong, and Central South University, systematically investigated Pb(Lu_1/2Nb_1/2)O₃ (PLN)-based antiferroelectric materials, and revealed their atomic-scale structural evolution and polarization reorientation mechanisms.

The researchers employed aberration-corrected high-angle annular dark-field scanning transmission electron microscopy to directly observe the atomic-scale polarization behavior. Imaging along the [001]_p direction revealed that PLN, PLN-2PT, and PLN-5PT all exhibited clear eightfold-periodic antiparallel Pb displacements; however, local regions in PLN-5PT showed period deviations, consistent with the diffuse scattering observed in selected-area electron diffraction.

Critically, statistical polar plot analysis of Pb displacement vectors revealed an important evolutionary trend: With increasing Ti content, the direction of Pb displacement gradually rotated from ~45°/-135° in pure PLN to ~30°/-120°, enabling continuous tuning of the in-plane polarization direction.

First-principles calculations indicated that Ti doping induced a rotation of polarization from in-plane to out-of-plane and reduced the antiferroelectric-ferroelectric phase transition energy barrier. This three-dimensional polarization pre-alignment effect significantly lowered the rotational energy barrier required for the electric-field-driven transition from the antiferroelectric state to the ferroelectric <111>_p state, explaining at the atomic structural level the experimentally observed reduction in critical field and enhanced ferroelectricity.

This mechanism is fundamentally distinct from the in-plane collinear "↑↑↓↓" model in classical PbZrO₃, providing a new design paradigm for the functional optimization of complex antiferroelectric systems.