Low-temperature synthesis of thermally stable BaWO4:Yb3+:Ho3+ nanophosphors: Tuning visible emission by controlling activator ion concentration

Upconverting nanophosphors are a special class of luminescent nanomaterials where lanthanide dopant assisted anti-stokes emission is exploited to achieve a wide range of applications. Herein we report Yb3+/Ho3+ co-doped BaWO4 nanophosphor with a significant thermal and chemical stability synthesized by a low-temperature hydrothermal process with red (655 nm) and green (538 nm) double color upconversion (UC) under 980 nm near-infrared (NIR) excitation, resulting in yellow emission. The synthesized samples were characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Vis-NIR Spectroscopy and Transmission Electron Microscopy (TEM) techniques. The dependence of emission behavior on various concentrations of activator ion (Ho3+) in BaWO4:Yb3+:Ho3+ phosphors were studied in detail. Temperature dependent emission spectra revealed that the phosphor possesses stable emission up to 200 degrees C and luminescence intensity drop of only 11.5% of the initial luminescence intensity was observed at 150 degrees C. Therefore, the luminescence behavior and the thermal stability of the phosphor suggest an effective pathway in the optoelectronic applications.