Effect of concentration of Er3+ on up‐conversion luminescence in NaYF4 containing oxy‐fluoride glass‐ceramics

The color of micro‐structured glass can be tuned by adjusting the cross‐relaxation between Er3+ ions through the mechanism of up‐conversion, although the range of color change is very limited. Here, we report the simple and reproducible synthesis of transparent oxy‐fluoride glass‐ceramics co‐doped with Yb3+/Er3+ by melting and secondary heat treatment. By adjusting the doping content of Er3+ ions from 0.2 to 10 mol%, followed by the secondary heat treatment, the intensity of up‐conversion luminescence under 980 nm laser excitation was increased by more than 100 times, and the glass‐ceramics showed an Er3+ doping content‐depended color change of the up‐conversion luminescence from green light to red light. The elemental analysis with TEM–EDS mapping and the measurement of the lifetime of up‐conversion luminescence suggest that changes in the cross‐relaxation between Er3+ ions is the principal mechanism behind the color change of up‐conversion luminescence. As a result, the red emission due to the electronic transition of 4F9/2 is much greater than that of the green emission (4S3/2). Therefore, we present a simple and reproducible strategy to achieve an efficient up‐conversion luminescence from glass‐ceramics with a broad range of color tunability and high color purity.