BaGeTeO6: Er3+, Yb3+ Fluorescent Materials Reveal a New Frontier in Fir Based Optical Temperature Sensing and Fluorescence Anti-Counterfeiting

Materials exhibiting up-conversion luminescence with rare earth ions have found extensive applications in anti-counterfeiting technologies. However, the practical realization of dual-mode photoluminescence poses challenges in meeting the increasingly complex requirements of modern anti-counterfeiting measures. This study introduces a novel approach, successfully synthesizing dual-mode excitation, dual-color emission Yb3+/Er3+ co-doped BaGeTeO6 phosphors through a single-step high-temperature solid-state method. The BaGeTeO6:Yb3+/Er3+ phosphor demonstrates simultaneous green and red emission under 980 nm excitation, with the emitted color transitioning from green to red by controlling the dopant concentrations. Conversely, under 1550 nm excitation, primarily a single-band red emission is observed. The inclusion of multi-color emissions enhances the security of multi-mode anti-counterfeiting measures. The potential up-conversion mechanisms under different excitation sources at 980 and 1550 nm were systematically investigated. Additionally, the anti-counterfeiting efficacy of the synthesized phosphor was assessed based on the intensity ratio of red and green emissions. Furthermore, it has been found that optimizing the molar ratio between Er3+ and Yb3+ ions improves the performance of the examined materials, making them suitable for use as a high-quality optical thermometer employing the FIR technique. Our results indicate promising prospects for the application of BaGeTeO6:Er3+/Yb3+ in the field of anti-counterfeiting.