Integrated visualizations and invisible encryptions for anti-counterfeiting in (K0.5Na0.5)NbO3-based ceramics induced by dynamic photochromic self-bleaching behavior

Abstract

Owing to the difficulty in replication and high security, delayed anti-counterfeiting is an emerging technology for its applicability in encrypting high-precision devices. Materials with photochromic (PC) effects and self-recovery behavior are appropriate candidates for realizing delayed anti-counterfeiting. Herein, Dy³⁺-doped (K_0.5Na_0.5)NbO₃-based ceramics were designed and prepared via tape-casting method. Down-conversion photoluminescence with white emission, conspicuous PC reaction and dynamic PC self-bleaching process were observed in the ceramics. The concentrations and positions of different defect traps, along with the oxygen vacancies of the ceramics, contributed to PC self-recovery. Taking advantage of the difference in PC self-recovery rates between yellow and blue emissions with time and the difference in color temperatures (C.T.), we propose a method of encrypting, calibrating, and performing C.T. detection on the nodes and paths of a single ceramic for optical signal input. This study will guide the construction of visual-invisible double-encryption anti-counterfeiting systems based on other novel materials.