Fabrication and luminescent properties of rare earths-doped Gd 2(WO 4) 3 thin film phosphors by Pechini sol–gel process

Abstract

Rare earth ions (Eu 3+ and Dy 3+)-doped Gd 2(WO 4) 3 phosphor films were prepared by a Pechini sol–gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM) and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting powders and films. The results of XRD indicate that the films begin to crystallize at 600°C and the crystallinity increases with the elevation of annealing temperatures. The film is uniform and crack-free, mainly consists of closely packed fine particles with an average grain size of 80 nm. Owing to an energy transfer from WO 4 2− groups, the rare earth ions show their characteristic emissions in crystalline Gd 2(WO 4) 3 phosphor films, i.e., 5D J– 7F J′ ( J=0, 1, 2, 3; J′=0, 1, 2, 3, 4, not in all cases) transitions for Eu 3+ and 4F 9/2– 6H J ( J=13/2, 15/2) transitions for Dy 3+, with the hypersensitive transitions 5D 0– 7F 2 (Eu 3+) and 4F 9/2– 6H 13/2 (Dy 3+) being the most prominent groups, respectively. Both the lifetimes and PL intensity of the Eu 3+ ( 5D 0 ) and Dy 3+ ( 4F 9/2 ) increase with increasing the annealing temperature from 500°C to 800°C, and the optimum doping concentrations for Eu 3+ and Dy 3+ are determined to be 30 and 6 at% of Gd 3+ in Gd 2(WO 4) 3 film host lattices, respectively.