Structure, luminescence of Eu<sup>2+</sup> and Eu<sup>3+</sup> in CaMgSi<sub>2</sub>O<sub>6</sub> and their co-existence for the excitation-wavelength/temperature driven colour evolution
Fang Su, Weijie Zhou, Yunlin Yang, Yiyi Ou, Zeming Qi, Chang‐Kui Duan, M.G. Brik, P. Dorenbos, H. Liang
Abstract
Luminescent materials with controllable colour evolution features are demanded for the development of multi-level anti-counterfeiting technologies. Here we report the structural and luminescence properties of CaMgSi2O6:Ln (Ln = Eu2+, Eu3+, Eu2+/3+) samples in detail and reveal their excitation-wavelength/temperature driven colour evolution characteristics. By tuning either the excitation-wavelength (276, 304, 343, 394 nm) or temperature (in the 330-505 K range), the designed samples with co-existing Eu2+/Eu3+ ions can achieve diverse and controllable colour evolution from red, to pink, purple and blue. This shows their potential application in anti-counterfeiting with the help of sophisticated pattern design. In addition, the underlying mechanism of the Stokes shift of the Eu2+ emission and valence stability of both Eu2+/Eu3+ ions in CaMgSi2O6 are also studied in depth. These results are valuable for designing colour-controllable luminescent materials based on the co-existence of the Eu2+/Eu3+ ions for anti-counterfeiting applications.