Synthesis and Properties of Nano-Sized ZnWO4:Eu3+ Phosphors by Hydrothermal Method

Abstract

ZnWO₄:Eu³⁺ phosphors were synthesized by the hydrothermal method at different conditions. The phase structure, morphology and luminescent properties of the as-synthesized samples were characterized by X-ray diffraction, scanning electron microscope and fluorescence spectrophotometer, respectively. The results indicate that all of the ZnWO₄:Eu³⁺ phosphors are pure monoclinic structure. The ZnWO₄:Eu³⁺ samples are spherical nanoparticles and the particle size of samples increases a little with increasing the hydrothermal temperature and time. The excitation spectrum of ZnWO₄:Eu³⁺ shows a broad excitation band extending from 220 to 350 nm and a series of sharp excitation peaks between 350 and 500 nm. The emission spectrum of the sample ZnWO₄:Eu³⁺ under the excitation at 301 nm is composed of the weak broad band attributing to the intrinsic emission of WO₄^2- groups and a series of sharp emission peaks originating from the characteristic emission of Eu³⁺. The emission intensity of Eu³⁺ at 616 nm reaches the strongest when the pH value is 6, the hydrothermal temperature is 180 °C, the hydrothermal time is 12 h and the Eu³⁺ concentration is 2 mol. % under the excitation at 301 nm. Meanwhile, it is found that the emission intensity of Eu³⁺ at 616 nm reach the highest when Eu³⁺ concentration is 6 mol. % under the excitation at 395 and 465 nm. Moreover, the photoluminescence colour of the sample can be tuned from blue, white and orange to red by adjusting the relative doping concentrations of Eu³⁺ in ZnWO₄:Eu³⁺.