TOF SIMS analysis and generation of white photoluminescence from strontium silicate codoped with europium and terbium

Abstract

White light emitting terbium (Tb3+) and europium (Eu3+) codoped strontium silicate (Sr2SiO4) phosphors were prepared by a solid state reaction process. The structure, particle morphology, chemical composition, ion distribution, photoluminescence (PL), and decay characteristics of the phosphors were analyzed by x-ray diffraction (XRD), scanning electron microscopy (SEM), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and PL spectroscopy, respectively. The XRD data showed that our Sr2SiO4 composed of two phases, namely, β-Sr2SiO4 and α′-Sr2SiO4, and the α′-Sr2SiO4 phase was more prominent than the β-Sr2SiO4 phase. The SEM micrographs showed that the particles were agglomerated together and they did not have definite shapes. All ions (i.e., negative and positive) present in our materials were identified by TOF-SIMS. In addition, the chemical imaging performed with the TOF-SIMS demonstrated how the individual ions including the dopants (Eu3+ and Tb3+) were distributed in the host lattice. White photoluminescence was observed when the Sr2SiO4:Tb3+, Eu3+ phosphor was excited at 239 nm using a monochromatized xenon lamp as the excitation source. The phosphor exhibited fast decay lifetimes implying that it is not a good candidate for long afterglow applications.