Color changing from white to red emission for ZnWO4:Eu3+ nanophosphors at different temperature

ZnWO4:Eu3+ nanoparticles were prepared via a simple refluxing method, followed by post-deposition annealing at 900 °C for 2 h. Field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), and photoluminescence (PL) spectra were used to investigate the morphology, structure and luminescent properties. The spectra of ZnWO4:Eu3+ phosphors were measured in the temperature range of 40-363 K. The broadband emission arises from the intrinsic WO42− groups, and the characteristic emission of Eu3+ ions increases with temperature increase. As a result, under the excitation at 254 nm, ZnWO4:Eu3+ phosphors emit white light at low temperature and red light at high temperatures, as it can be observed by naked eyes. This can be explained by the different energy transfer efficiency from WO42− groups to Eu3+ ions in ZnWO4:Eu3+ phosphors at the different temperatures.