Preparation, patterning and luminescent properties of oxyapatite La_9.33(SiO₆)₄O₂:A(A   Eu³, Tb³, Ce³) phosphor films by sol gel soft lithography

Abstract

Silicate oxyapatite La9.33(SiO6)4O2:A (A = Eu3+, Tb3+ and/or Ce3+) phosphor films and their patterning were fabricated by a sol–gel process combined with soft lithography. X-ray diffraction(XRD), Fourier transform infrared spectroscopy, atomic force microscopy, optical microscopy and photoluminescence spectra, as well as lifetimes, were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 800 °C and the crystallinity increased with the increase in annealing temperatures. Transparent nonpatterned phosphor films were uniform and crack-free, which mainly consisted of rodlike grains with a size between 150 and 210 nm. Patterned thin films with different bandwidths(20, 50µm) were obtained by the micromoulding in capillaries technique. The doped rare earth ions(Eu3+, Tb3+ and Ce3+) showed their characteristic emission in crystalline La9.33(SiO6)4O2 phosphor films, i.e. Eu3+5D 0 −−7FJ(J = 0, 1, 2, 3, 4), Tb3+5D 3,4 −−7FJ(J = 3, 4, 5, 6) and Ce3+ 5d(2D)−− 4f(2F 2/5,2F 2/7) emissions, respectively. Both the lifetimes and PL intensity of the Eu3+, Tb3+ ions increased with increasing annealing temperature from 800 to 1100 °C, and the optimum concentrations for Eu3+, Tb3+ were determined to be 9 and 7 mol% of La3+ in La9.33(SiO6)4O2 films, respectively. An energy transfer from Ce3+ to Tb3+ was observed in the La9.33(SiO6)4O2:Ce, Tb phosphor films, and the energy transfer efficiency was estimated as a function of Tb3+ concentration.