Investigation on the upconversion luminescence of Sr3AlO4F:Yb3+, Er3+, Ho3+ phosphors

• New upconversion phosphors of Sr3AlO4F:Yb3+,Er3+,Ho3+ were developed.
• Tunable emission has been obtained in the Sr3AlO4F:5%Yb3+,xEr3+,yHo3+ phosphors.
• Sr3AlO4F:Yb3+,Er3+ shows a red emission peak and the green one is almost quenched.

To develop new emission-tunable upconversion (UC) phosphors, the Sr3AlO4F:5%Yb3+, xEr3+, yHo3+ (0 ≤ x ≤ 1%, 0 ≤ y ≤ 1%) samples were prepared by conversional solid-state reaction method, and their luminescence properties upon 980 nm excitation were studied. Upon 980 nm excitation, Yb3+-Er3+ codoped Sr3AlO4F shows a predominant emission peak between 645 and 700 nm which is attributed to the 4F9/2-4I15/2 transition of Er3+, and the Er3+ green emissions have been almost quenched. In this case, the yellowish green emitting light is obtained. The possible reason was interpreted by the energy level diagram and the proposed UC mechanism. For Yb3+-Ho3+ codoped Sr3AlO4F, three emissions are observed obviously which are all derived from the Ho3+ ion. The corresponding chromaticity coordinates indicate a red emission has been gained. To realize the tunable emission, the typical Sr3AlO4F:5%Yb3+, 0.2%Er3+, 1%Ho3+ phosphor was developed, and its emission spectrum includes the emission peaks of both Er3+ and Ho3+. Correspondingly, the sample gives a yellow emission.

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