NIR to VIS frequency upconversion luminescence properties of Er3+-doped YPO4 phosphors

Different concentrations of Er3+-doped YPO4:Er powder phosphors have been synthesized by the conventional solid state reaction method and are characterized by X-ray diffraction (XRD), field emission scanning electronic microscopy (FESEM), and upconversion emission measurements. An intense red emission band and a weak green emission band are observed under NIR excitation at 975 nm in case of samples with high dopant concentration while no upconversion emission was observed at lower Er3+ ion concentrations. The possible mechanisms involved in the upconversion process have been discussed in comparison to results with similar reported works.