Effect of Al2O3/SiO2 ratio on the structure and luminescence properties of Eu3+/Yb3+ co-doped Na2O–CaO–SiO2–Al2O3–ZnO–F glasses

Abstract

The Eu3+/Yb3+ co-doped Na2O–CaO–SiO2–Al2O3–ZnO–F glasses were prepared. Various Al2O3/SiO2 ratios were used and their impact on the structure and optical properties of the glasses was examined. The results indicate that as the content of Al2O3 increases, the propensity for precipitation in the glass intensifies, while its thermal stability diminishes. The transmission spectra reveal that the incorporation of Al2O3 causes a shift towards longer wavelengths in the UV cut-off point of the glasses, which can be attributed to the alteration of the glass's network structure. Consequently, there is an increase in the amount of non-bridging oxygens present, ultimately resulting in a reduction of the optical bandgap. The analysis of luminescent properties suggests that as the Al2O3/SiO2 ratio increases, the luminescence intensity of the Eu3+ ion also increases but that of the Yb3+ ion decreases. The reason for this is that the Al2O3 added to the glass disrupts the symmetry of the surrounding environment where Eu3+ ions exist. As a result, the likelihood of electric dipole transition for these ions is enhanced. Simultaneously, it disrupts the glass network and increases the distance between rare earth ions, leading to a reduction in the luminescence intensity of Yb3+ ions. In addition, the energy transfer process of Eu3+→Yb3+ has potential application prospects in improving the efficiency of silicon-based solar cells by converting ultraviolet light into infrared light.