Electric-field-modulated luminescence in highly stable and transparent Er-doped PMN-PT crystals

Relaxor ferroelectric single crystals, epitomized by PMN-PT, exhibit giant piezoelectricity but are intrinsically bottlenecked by their vulnerability to electric-field-induced depolarization and severe optical opacity caused by complex domain wall scattering. Herein, we propose a synergistic strategy integrating B-site defect engineering and alternating current (AC) domain engineering to construct a highly stable, transparent, and multifunctional Er³⁺-doped PMN-PT single crystal. Ion radius difference drives Er³⁺ to preferentially occupy the perovskite B-site, spontaneously generating Er-oxygen vacancy defect dipoles. These dipoles serve as robust pinning centers, constructing an internal bias field that significantly enhances the coercive field and electromechanical stability, while simultaneously achieving a giant piezoelectric coefficient ( d ₃₃ ∼ 2300 pC/N) at the morphotropic phase boundary. Furthermore, AC-poling selectively annihilates the light-scattering 71° domain walls, reshaping the crystal into a highly ordered “2R” macroscopic domain state and boosting optical transmittance to nearly 70%. Capitalizing on this highly transparent optical window, the intrinsic luminescence of Er³⁺ is fully liberated. Notably, we discover a unique three-stage, non-monotonic electric-field modulation of photoluminescence intensity, which fundamentally maps the intricate dynamics from the intrinsic electro-optic effect to polar nanoregions (PNRs) competition and eventual macroscopic domain reconfiguration. This work not only resolves the long-standing trade-off between piezoelectric stability and optical transparency but also establishes a compelling materials paradigm for next-generation piezoelectric-optoelectronic coupled devices and smart sensors.