Effect of divalent dopants, Zn2＋ ion, on the high-order photon avalanche （PA） upconversion （UC） emission of Er3＋ doped BiOCl microcrystals was investigated. XRD results indicated that Zn2＋ ion dopants would mostly enter into the lattice space at low and moderate doping concentration, and began to substitute Bi3＋ ion gradually at heavily doping level. Under exaction at 980 nm, the PA UC of violet, green and red emission of Er3＋ ions could be observed, and the UC emission intensity increased with increasing the Zn2＋ addition below 8 mol.%, then decreased with further addition. Power dependence study showed that the dopant concentration of Zn2＋ had no obviously negative effect on the occurrence of PA emission. On the bases of results investigated herein, we considered that the lattice distortion by Zn2＋ doping could not directly change the special PA emission of BiOCI：Er3＋, but would improve the emission intensity when used as lattice modifier.
The green long-after-glow luminescence from Tb3＋-doped Sr2SiO4 phosphors, which are synthesized by the high temperature solid state reaction in a reductive atmosphere, is observed in this paper. The results show that under ultraviolet excitation, the obtained phosphors produce an intense green-lighting-emission from the Tb3＋, and the green-lighting long- after-glow luminescence related to Tb3＋ can last half an hour after the irradiation source has been removed. Moreover, the effects of co-doping Li＋, Dy3＋, Er3＋, Gd3＋, and Yb3＋ with Tb3＋ on the decay properties and thermoluminescence properties are investigated to confirm the long-after-glow mechanism.
Tetragonal structure La1-xBixOCl polycrystals were prepared by solid state synthesis. With increase in bismuth content, the morphology of the prepared samples changed from non-oriented particles to layered crystals and the broadband blue-white emission from LaOCl polycrystals decreased dramatically. Comparative experiments and X-ray photoelectron spectroscopy（XPS） analysis indicated that the host emission more possibly originated from Cl self-doping in oxychloride crystals. According to a close composition relationship of the Cl self-doping behavior and crystal morphology, it was suggested that the La composition strengthened the interlayer interaction between Cl^– anion and crystal cell lamellar, hindering the orientation of LaOCl crystals. The results of our work would deepen the understanding of the orientation structure of tetragonal oxyhalides and offer an insight into the origin of its host luminescence.
The exploration of novel long lasting red phosphors is still of importance due to expected commercial applications and scientific interests. In this work, we reported the red long lasting phosphorescence（LLP） from Eu^3＋ doped BiOCl semiconductor polycrystals. The LLP property of the red phosphor is relatively weak due to less trap density, but the excitation band of LLP stems from the energy gap transition of semiconductor, offering experimental evidence for energy transfer between BiOCl semiconductor and Eu^3＋ ions. Although the afterglow duration of Eu^3＋ doped BiOCl was short temporarily, this work may open a novel kind of red LLP phosphors.
A transparent glass ceramic tri-doped with Ce3＋/Er3＋/yb3＋ was fabricated by the high-temperature melting technique and following heat-treatment. X-ray diffraction and transmission electron microscope results demonstrated that Cas（PO4）3F（FAP） nanocrystals, possessed with preferable emission performances for the 1.54 μm transition for doping Er3＋, were homogeneously pre- cipitated among the glass matrix with a mean size of 30 rim. Addition of Ce3＋ greatly enhanced 1.54 ~tm fluorescence of Er3＋ by the cross relaxation energy transfer between Er3＋ and Ce3＋. Meanwhile, incorporation of Ce3＋ dramatically decreased the visible upcon- version emission intensity of glass ceramic than that of glass, suggesting that Ce3＋ might incorporate into the FAP nanocrystals. The properties of this transparent glass ceramic showed the potential application as an efficient 980 nm pumped infrared laser medium.
