Reversible and color controllable emissions in Er3+/Pr3+-codoped K0.5Na0.5NbO3 ceramics with splendid photochromic properties for anti-counterfeiting applications

It is highly significant to develop multi-mode optical anti-counterfeiting materials to efficiently fight against counterfeit products. In this study, we chose ferroelectric K0.5Na0.5NbO3 (KNN) with excellent photochromism properties as the host and rare-earth Er3+ and Pr3+ ions as dopants to prepare the Er3+/Pr3+-codoped KNN ceramics. The color-tunable emissions can be obtained from red-orange-yellow to green by controlling the excitation wavelength. Upon 980 nm excitation, the synthesized ceramics does not only have superior upconversion (UC) emission behaviors but also have good luminescence modulation properties based on the photochromism properties. It is found that the KNN:0.003Er(3+)/0.003Pr(3+) sample with the optimal UC emission features shows a highest.Rt value of 74.52% when irradiated by 390 nm light for 5 min, whereas the KNN:0.005Er(3+)/0.003Pr(3+) ceramics also exhibit a high Delta R-t value of 66.81% under 395 nm light irradiation. According to the XPS and EPR results, one knows that the mechanism of luminescence modulation is closely related to defects and traps caused by the oxygen vacancies. Furthermore, the optical information writing and erasing test is conducted, exhibiting a good reproducibility and fatigue resistance. These results reveal that the designed ceramics are appropriate for the anti-counterfeiting applications.

Automated summary

This study developed color-tunable emissions in Er3+/Pr3+-codoped KNN ceramics using ferroelectric K0.5Na0.5NbO3 as a host material. The ceramics exhibited superior upconversion emission behaviors and luminescence modulation properties based on photochromism. The mechanism of luminescence modulation is related to defects and traps caused by oxygen vacancies, making these ceramics suitable for anti-counterfeiting applications.