Effects R³⁺on the photoluminescent properties of Ca₂R₈(SiO₄)₆O₂:A (R = Y,La,Gd;A = Eu³⁺,Tb³⁺) phosphor films prepared by the sol–gel process

Abstract

Using CaCO3, metal oxides (all dissolved by nitric acid) and tetraethoxysilane Si(OC2H5)4 (TEOS) as the main starting materials, Ca2R8(SiO4)6O2:A (R = Y,La,Gd;A = Eu3+,Tb3+) phosphor films have been dip-coated on quartz glass substrates through the sol–gel process. X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM) and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the 1000 °C annealed films are isomorphous and crystallize with the silicate oxyapatite structure. AFM and SEM studies revealed that the phosphor films consisted of homogeneous particles ranging from 30 to 90 nm, with an average thickness of 1.30 µm. The Eu3+ and Tb3+ show similar spectral properties independent of R3+ in the films due to their isomorphous crystal structures. However, both the emission intensity and lifetimes of Eu3+ and Tb3+ in Ca2R8(SiO4)6O2 (R = Y, La, Gd) films decrease in the sequence of R = Gd>R = Y>R = La, which have been explained in accordance with the crystal structures.