Search

Abstract: A comparative analysis of the luminescent properties of YAG and YAG:Ce nanopowders (NP) in comparison with single crystalline film (SCF) and single crystal (SC) analogues was performed under excitation by a pulsed synchrotron and X-ray radiation. It was shown that the natural defects concentration in NP was between the SC with a large (∼0.18–0.19at.%) concentration of YAl antisite defects (AD) and SCF of these garnets where YAl AD were completely absent. At the same time, Ce3+ doped YAG NP showed luminescent properties close to those of YAG:Ce SCF. [Copyright &y& Elsevier]

Abstract: Ca1− x Eu x Al4O7 (x =0, 0.002, 0.01, 0.02, 0.05, 0.1) and Ca1−2 x Eu x Na x Al4O7 (x =0.002, 0.02, 0.05, 0.1) crystalline phosphor powders have been synthesized by modified Pechini method and their spectroscopic properties at room and liquid nitrogen temperature were measured. Excitation spectra of synthesized materials contain broad band attributed to ligand to metal, O2−→Eu3+, charge transfer absorption and narrow lines related to 7F0→5D J , 5H J , 5L J , 5G J transitions of europium ions. Upon excitation at 395nm, the Eu3+-doped calcium dialuminates exhibit red photoluminescence due to parity forbidden f–f intra-configurational transitions with the most intense component at 612nm resulting from the 5D0→7F2 hypersensitive transition. The quantum efficiency of the powders emissions does not exceed 12%. The luminescence decay kinetics reveals that some quenching appears for higher concentrations. Site selective spectroscopy disclosed the presence of at least two well defined individual spectroscopic sites of Eu3+ and increasing disturbance of their local symmetries with raising concentration of the activator was observed. The increasing symmetry disorder led to a significant asymmetrical broadening of the luminescence lines at higher concentrations. Concentration dependence of the luminescence kinetics of the two diverse Eu3+ ions is different, as only one of them, with the characteristic luminescence at 579.5nm, exhibits shortening of the decay time at higher Eu contents. The inexpensive CaAl4O7:Eu powders are potentially good candidates for photonics applications. For Eu, Na co-doped powders the Eu3+ ions producing emission at 579.7nm dominates strongly over those with luminescence at 577.2nm. [Copyright &y& Elsevier]

The sol–gel derived synthesis of TiO2 films doped with Lu2O3:Tb3+ nanocrystallites and deposited on quartz or silicon substrates has been described. Their morphology have been determined by the SEM techniques. The transmission, photoluminescence and cathodoluminescence spectra have been measured. The emission decays have been measured and lifetimes for starting nanocrystalline powders and embedded nanocrystallites have been determinated. A strong influence of TiO2 matrix on the emission properties of embedded Lu2O3:Tb3+ nanocrystallites was found. [Copyright &y& Elsevier]