Growth and optical properties of nanocrystalline Gd3Ga5O12:Ln (Ln=Eu3+,Tb3+,Er3+) powders and thin films via Pechini sol-gel process

Rare earth (Eu3+, Tb3+, Er3+)-doped gadolinium gallium garnet (Gd3Ga5O12, GGG) nanocrystalline powder and thin film phosphors were prepared by the Pechini sol-gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM) as well as photoluminescence (PL) spectra were used to characterize the resulting powder and film samples. Both the powders and the coatings crystallized completely at 800 °C. The dopant rare earth ions show their characteristic emissions in Gd3Ga5O12 phosphors, i.e., 5D0-7FJ(J=1,2,3,4) transitions for Eu3+, 5D4-7FJ(J=3,4,5,6) transitions for Tb3+ and (2H11/2-4I15/2, 4S3/2-4I15/2) transitions for Er3+, respectively. In addition, the near infrared emission spectra (NIR) and the near infrared to visible upconversion (anti-Stokes) luminescence of Er3+ were also observed in the Er3+-doped Gd3Ga5O12 samples. Possible mechanism responsible for the upconversion luminescence of Er3+ was proposed.