Up-conversion luminescence of Tm3+ sensitized by Yb3+ ions in GdVO4

The aim of this work is to study up-conversion (UPC) luminescence in a series of Tm3+/Yb3+-co-doped GdVO4 samples synthesized by the solid-state method. The concentrations of Yb3+ ions were 3, 6 and 9 mol.%, while the concentration of Tm3+ ions was fixed (3 mol.%). X-ray diffraction patterns for all the synthesized samples confirmed successful formation of a pure GdVO4 phase. Quantitative energy-dispersion x-ray analysis confirmed successful doping of Tm3+ and Yb3+ ions into the GdVO4 matrix. Scanning electron microscope images show that the samples are composed of deformed (irregular) spherical particles with an average diameter size in the range of 1.4 − 8.4 μm. Up-converted emission spectra were recorded at room temperature under 980 nm excitation. It was found that all our samples exhibit UPC emission in three different spectral regions: strong emissions are observed at 475 and 800 nm corresponding to the 1G4 → 3H6 and 3H4 → 3H6 transitions, respectively, while emission in the red region at about 650 nm is very weak and is due to the 1G4 → 3F4 transition. It was concluded that conversion of near-infrared radiation into blue emission proved to be very effective in all the synthesized systems. It was found that emission decay curves for all samples exhibit single exponential behavior.