Intense ultraviolet and blue upconversion emissions in Yb 3+–Tm 3+ codoped stoichiometric Y 7O 6F 9 powder

Abstract

Stoichiometric Y 7O 6F 9 powder codoped with Yb 3+–Tm 3+ was synthesized via co-precipitation and subsequent calcining route. The results of X-ray diffraction and transmission electron microscopy reveal that when the calcining temperature is beyond 800 °C, orthorhombic YF 3 nanoparticles can be completely oxidized into orthorhombic Y 7O 6F 9 powder. Under the excitation of a 980 nm laser, Y 7O 6F 9 powder exhibits multicolor UC emission in regions spanning the UV to the NIR. In addition, the upconversion emission intensities of YF 3, Y 7O 6F 9 and Y 2O 3 powders were compared under the same dopant condition (Yb/Tm=5/0.5 mol%). The low phonon energy revealed by Raman spectra helped to understand the high efficient upconversion emission of Y 7O 6F 9 and the main phonon vibration of Y 7O 6F 9 lies at 472 cm −1, which is far lower that of Y 2O 3 (at 708 cm −1). Our results indicate that orthorhombic rare earth ions doped Y 7O 6F 9 is an efficient matrix for UV and blue UC emission, and has potential applications in color displays, anti-counterfeiting and multicolor fluorescent labels.