Abstract

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.