(K0.5Na0.5)NbO3-based photochromic transparent ceramics for high-security dynamic anti-counterfeiting and optical storage applications

Abstract

Inorganic photochromic (PC) materials are increasingly considered as important media for optical information storage and multi-level encryption anti-counterfeiting. However, most traditional materials are based on their static properties, posing a serious security threat to the stored information. To address this issue, a strategy is proposed for kinetics-tunable PC (K0.5Na0.5)NbO3 ceramic that comprehensively utilize the static and dynamic characteristics of matters. The prepared (K0.5Na0.5)0.95Sr0.04Pr0.01NbO3 (SP-y) ceramics displayed two different excellent optical properties and distinct applications (smart windows and dynamic information storage) simply by adjusting sintering temperature (y). The sample SP-1180 exhibited high transparency (∼62% at 780 nm) while SP-1150 possessed ultrafast response time (3 s) and extremely high coloration contrast (ΔRI = 91%). More importantly, the kinetics of photoreaction could be modulated by varying illumination wavelength and time. Furthermore, a new anti-counterfeiting or optical storage method was designed by constructing SP-1150 with different PC properties. The encoded or stored information was recorded using two commercial lasers (370 & 405 nm or 370 & 520 nm), suggesting that the security level of this anti-counterfeiting design could be significantly improved. This work will drive more innovative designs in smart windows, high-security dynamic anti-counterfeiting and optical storage applications in the future.