Dual-functional Applications of Photochromic BiNbO4: Er3+ Ceramics Based on Reversible Upconversion Luminescence Modulation

Photochromic luminescent phosphor has attracted considerable attention owing to its excellent optical properties, which face the problem of limited applications. Herein, the reversible photochromic and photo-/thermal bleaching phenomenon of BiNbO4 ceramic was reported, exhibiting a color change between ivory and grey by alternating stimuli between 365/405 nm light illumination and 808 nm laser irradiation (or thermal treatment at 400 ℃). Their potential coloration mechanisms are explained by the color center model, providing a comprehensive framework for understanding the original processes. Through Er3+ ion doping, the maximum coloration contrast decreases from 24% to 20%, while simultaneously enabling the observation of bright green upconversion luminescence. Relying on the combination of re-absorption and energy transfer process, the upconversion luminescence intensity of the Er3+ ions can be effectively modulated, respectively showing a maximum regulation and recovery rate of 88.0% and 98.1%. The cycle measurements demonstrate the excellent anti-fatigue properties and reproducibility of BiNbO4: Er3+ ceramics, confirming their potential multi-functional applications in anti-counterfeiting and fingerprint acquisition.