Site Symmetry Of Eu3 Research Articles

Synthesis and the luminescent properties of europium-activated Ca2SnO4 phosphors

Abstract The synthesis and photoluminescent (PL) properties of calcium stannate crystals doped with europium grown by mechanically activated in a high energy vibro-mill have been investigated. The characteristics of Ca2SnO4:Eu3+ phosphors were found to depend on the amounts of europium ions. The XRD profiles revealed that the system, (Ca1−xEux)2SnO4, could form stable solid solutions in the composition range of x = 0–7% after being calcined at 1200 °C. The calcined powders emit bright red luminescence centered at 618 nm due to 5D0 → 7F2 electric dipole transition. Both XRD data and the emission ratio of (5D0 → 7F2)/(5D0 → 7F1) reveal that the site symmetry of Eu3+ ions decreases with increasing doping concentration. The maximum PL intensity has been obtained for 7 mol% concentration of Eu3+ in Ca2SnO4.

Local structure and persistent spectral hole burning of the Eu3+ ion in SnO2–SiO2 glass containing SnO2 nanocrystals

The local structure and persistent spectral hole burning (PSHB) of the Eu3+ ion in SnO2–SiO2 glass containing SnO2 nanocrystals were investigated. The excitation and emission spectra of the Eu3+ ions indicate that the Eu3+ ions are doped into the SnO2 nanocrystals and glass phases. The variation in the site symmetry of Eu3+ ions in the nanocrystal from D2h or C2h symmetry may be due to oxygen vacancies. Fluorescence line-narrowing spectra reveal that the Eu3+ ions in the glass phase have two sites, one of which exhibits a unique feature. The calculated second crystal-field parameters show that the coordinating oxygen ions of site I are closer to the Eu3+ ions with increasing excitation energy, while those of site II are farther away from the Eu3+ ions. This result leads to the opposite behavior of the fluorescence lines of the Eu3+ ions at the two sites. PSHB was also observed and multiholes with a narrow width can be burned in the SnO2–SiO2 glass containing SnO2 nanocrystals.

Synthesis of Y3Al5O12:Eu3+ phosphor by sol-gel method and its luminescence behavior

The Eu3+-doped Y3Al5O12 phosphor ultrafine powders were synthesized by the sol–gel method using metal alkoxide at the lower temperature of 1000°C. The formation process and structure of the phosphor powders were investigated by means of TG-DTA, XRD and SEM. It has been found that the phosphor powders were amorphous up to 700°C and changed into the single phase YAG at about 1000°C, that is, 600°C lower than that required for the constituent oxide mixtures. The resulting ultrafine, phase-pure, cubic yttrium aluminum garnet (YAG) phosphor powders were obtained. In the course of the phosphor transformation from non-crystalline state to crystalline state, both the emission intensity and the site symmetry of Eu3+ in the phosphors varied noticeably. The Eu3+ emission intensity of 5D0→7F1 and 5D0→7F2 versus Eu3+ concentration and sintering temperature was studied.

Luminescence and crystal field parameters of the Na 3[Eu(DPA) 3]·12H 2O complex in a single crystalline state

Single crystals of Na 3[Eu(DPA) 3]·12H 2O (DPA=dipicolinato) were grown by the temperature lowering method. Luminescence and excitation spectra of the crystals are reported. Detailed line assignments for the 5D 0→ 7F J ( J=0, 1, 2, 3 and 4) transitions are carried out with the simulation of the luminescence lines in the frame of the free-ion and the crystal-field Hamiltonians. Although the systematic analysis on the baricenter shifting of each excited J states due to the complexation is need for the emission process, the set of the refined crystal field parameters under the D 2 site symmetry satisfactorily reproduces the fine splitting of the emission lines. It proves the fact that the characteristic line splittings are strongly correlated with the site symmetry of Eu(III).

Energy Transfer Between Rare Earth Ions in a Potassium Feldspar Glass

Nonradiative energy transfer was observed between rare earth ions in a potassium feldspar glass. Observation was made of the quenching of terbium fluorescence through interactions with dissimilar lanthanide ions. The severity of quenching is dependent on the energy gap between the fluorescing level of terbium and the closest lower lying level of another lanthanide ion and a numerical constant characteristic of the host. The value of this host constant, 2246 cm−1, is indicative of a high probability of phonon‐assisted energy transfer. Energy transfer was also observed between dysprosium and samarium when 405 and 425 nm radiation was used for excitation. The site symmetry of Eu3+ in potassium feldspar glass was evaluated through analysis of the emission spectrum and appears to be .

Site symmetry of Eu3+ in flux-grown zircon

Site symmetry of Eu3+ in flux-grown zircon

Vibronic Structure in Luminescence Spectra of Rare Earth Ions In SrTiO3, BaTiO3 and Other Perovskites

In the luminescence spectra of Eu 3+ in SrTiO 3 , two kinds of vibronic structure, i.e. , rather sharp satellite lines (vibronic lines) and asymmetric bands (vibronic tails), were found to exist. The tails were observed also in the spectra of Tb 3+ and Pr 3+ in SrTiO 3 . The tail strongly appears associated only with transitions allowed by forccd electric dipole. A comparison of the luminescence spectra of Eu 3+ in SrTiO 3 and BaTiO 3 has suggested the existence of a correlation between the strength of vibronic structure and the site symmetry of rare earth ions. To investigate this, the luminescence spectra of Eu 3+ were studied in various perovskite type oxides in which the site symmetry of Eu 3+ varies from O h to very low symmetries. It has been clarified that the vibronic lines strongly appear when the site symmetry is O h or very close to it. However, the vibronic tail was observed only in SrTiO 3 . In order that the vibronic tail appears, some special properties of host material seem to be required.