We investigated the effects of annealing on the photoluminescence (PL) properties of a citrate-capped YVO4:Bi3+,Eu3+ nanophosphor. The 300 °C annealed nanophosphor exhibited the highest PL intensity at 619.5 nm corresponding to an f-f transition of Eu3+ under near-UV excitation. Fourier transform infrared spectroscopy indicated a decrease in the amounts of adsorbed water and citrate on the nanophosphor surface with annealing. Dehydration and the increase in near-UV absorption contributed to the improved PL intensity, since water is a Eu3+ luminescence quencher. The thermal decomposition of citrate, which photoreduces vanadate under near-UV irradiation, caused the improved photostability. Annealing at ≥400 °C decreased the PL intensity. A color change from white to yellow may be attributed to absorption by byproducts, possibly formed by the segregation of YVO4:Bi3+,Eu3+. A shorter PL lifetime and lower activation energy of thermal quenching at higher annealing temperature were confirmed from PL decay curves and the temperature dependence of PL intensity, respectively. The formation of surface defects resulted from the thermal decomposition of adsorbed citrate. The decrease in PL intensity was caused by the formation of byproducts and surface defects.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films