Deposition of NaGd(WO4)2:Eu3+/Bi3+ films on glass substrates and potential applications in white light emitting diodes

NaGd(WO 4 ) 2 :Eu 3+ /Bi 3+ films were deposited on SiO 2 glass substrates by spin-coating. The as-prepared films were heat treated at different temperatures. The properties of films were characterized by TG-DSC, XRD, SEM and fluorescence spectrophotometer. The TG-DSC curve indicated that films began to crystallize at about 600   °C. The XRD patterns and SEM images of films annealed at 600   °C, 700   °C and 800   °C showed that a higher temperature benefits to the higher crystallinity and induces the lower thickness. Meanwhile, it was found that the revolution of spin coating influenced the morphology of films obviously. Under the excitation at 396   nm, NaGd(WO 4 ) 2 :Eu 3+ /Bi 3+ films showed characteristic emission bands originating from 5 D 0   →   7 F j ( j   =   1, 2, 3, and 4) transitions of Eu 3+ ions. It was also found that the excitation wavelength has great effect on the emission intensity.