Sol–gel deposition and luminescent properties of oxyapatite Ca2(Y,Gd)8(SiO4)6O2 phosphor films doped with rare earth and lead ions

Rare-earth and lead ions (Eu3+, Tb3+, Dy3+, Pb2+) doped Ca2Y8(SiO4)6O2 and Ca2Gd8(SiO4)6O2 thin films have been dip-coated on silicon and quartz glass substrates through the sol–gel route. X-Ray diffraction (XRD), TG–DTA, scanning electron microscopy (SEM), atomic force microscopy (AFM), FT-IR and luminescence excitation and emission spectra as well as luminescence decays were used to characterize the resulting films. The results of XRD reveal that these films remain amorphous below 700 °C, begin to crystallize at 800 °C and crystallize completely around 1000 °C with an oxyapatite structure. The grain structure of the film can be seen clearly from SEM and AFM micrographs, where particles with various shapes and average size of 250 nm can be resolved. Eu3+ and Tb3+ show their characteristic red (5D0–7F2) and green (5D4–7F5) emission in the films with a quenching concentration of 10 and 6 mol% (of Y3+), respectively. The lifetime and emission intensity of Eu3+ increase with the temperature treatment from 700 to 1100 °C, while those of Tb3+ show a maximum at 800 °C. Energy transfer phenomena have been observed by activating the oxyapatite film host-lattice Ca2Gd8(SiO4)6O2 with Tb3+ (Dy3+). In addition, Pb2+ can sensitize the Gd3+ sublattice in Ca2Gd8(SiO4)6O2.