Emissions Of Eu Ions Research Articles

Effect of Oxygen Vacancies on the Reduction of Eu3+ in Mg3Ca3(PO4)4 in Air Atmosphere.

The paper reported the synthesis of mixed-valence Eu-doped Mg3Ca3(PO4)4 by solid-state reaction in the air atmosphere. The luminescence measurements indicated that the obtained phosphors exhibit a broad bluish-green fluorescence of Eu2+ and a sharp orange-red emission of Eu3+ excited by 395 nm. The abnormal reduction mechanism could be explained by a charge compensation model. A tunable luminescence was realized based on the reduction of Eu3+ to Eu2+ changed along with increasing the sintering time. The reduction of Eu3+ to Eu2+ in Mg3Ca3(PO4)4 host was effected by the oxygen vacancy defects when the samples sintered in different atmosphere and sintered for different lengths of time, and the oxygen vacancies which act as the electron traps were investigated with thermoluminescence. All of the results almost indicated the oxygen vacancy could weaken the reduction of Eu3+ to Eu2+. Our investigation of Mg3Ca3(PO4)4:Eu could provide a practical basis and theoretical basis to study the effect of oxygen vacancy on the emission of Eu ions.

Eu-doped ZnO–HfO2 hybrid nanocrystal-embedded low-loss glass-ceramic waveguides

We report on the sol–gel fabrication, using a dip-coating technique, of low-loss Eu-doped 70SiO2 – HfO2–xZnO (x = 2, 5, 7 and 10 mol%) ternary glass-ceramic planar waveguides. Transmission electron microscopy and grazing incident x-ray diffraction experiments confirm the controlled growth of hybrid nanocrystals with an average size of 3 nm–25 nm, composed of ZnO encapsulated by a thin layer of nanocrystalline HfO2, with an increase of ZnO concentration from x = 2 mol% to 10 mol% in the SiO2–HfO2 composite matrix. The effect of crystallization on the local environment of Eu ions, doped in the ZnO–HfO2 hybrid nanocrystal-embedded glass-ceramic matrix, is studied using photoluminescence spectra, wherein an intense mixed-valence state (divalent as well as trivalent) emission of Eu ions is observed. The existence of Eu2+ and Eu3+ in the SiO2–HfO2–ZnO ternary matrix is confirmed by x-ray photoelectron spectroscopy. Importantly, the Eu-doped ternary waveguides exhibit low propagation losses (0.3 ± 0.2 dB cm–1 at 632.8 nm) and optical transparency in the visible region of the electromagnetic spectrum, which makes ZnO–HfO2 nanocrystal-embedded SiO2–HfO2–ZnO waveguides a viable candidate for the development of on-chip, active, integrated optical devices.