Photoluminescence, photochromism and reversible optical modulation of La3+/Er3+/Yb3+ tri-doped K1-xNaxNbO3 ceramics

Abstract

Photochromic (PC) ceramics exhibiting multifunctional optical features hold significant promise for applications in real-time information storage, anti-counterfeiting technologies, and photoelectric energy conversion. However, conventional performance optimization strategies are predominantly confined to tuning the concentration of activators (e.g., rare-earth dopants) and frequently fail to overcome the intrinsic trade-off between optical transparency and PC efficiency. This study presents the development of a series of K_1-xNa_xNbO₃-based transparent ceramics tri-doped with fixed concentrations of La³⁺, Yb³⁺, and Er³⁺. By precisely tuning the K⁺/Na⁺ ratio via stoichiometric control, we systematically regulate defect charge compensation and the energy level depth of traps, thereby effectively decoupling the intrinsic performance trade-off. With increasing Na⁺ content, lattice contraction leads to elevated formation energies for critical defects and a reduction in trap energy levels, thereby inhibiting the effective capture of charge carriers and weakening the PC response. Large and reversible photoinduced luminescence modulation (∼80%) and optical transmittance modulation (∼91%) were achieved at x = 0 by alternating irradiation with a 405 nm laser and thermal stimulation at 300 °C. This study provides an in-depth investigation of the optical modulation mechanism and the formation model of multiple color centers, thereby expanding the applicability of PC materials in real-time and multi-dimensional optical recording.