I. V. Berezovskaya

Synthesis and luminescence properties of Eu2+-doped Li2SrSiO4

We have studied the luminescence spectra of Li2Sr1 − xEuxSiO4 (x = 0.0001–0.01) solid solutions prepared by solid-state reactions and a sol-gel process in a reducing atmosphere. The spectra show a broad band in the range 500–700 nm, centered at 578 nm, which is due to the 4f65d → 4f7 transition. The luminescence excitation spectrum shows, in addition to bands due to Eu2+ 4f7 → 4f65d transitions, a strong band centered at 174 nm, attributable to absorption in the SiO44− group.

Ln2+ stabilization in strontium borates

The effect of crystal structure on the stability of Ln2+ ions in strontium borates has been studied by luminescence spectroscopy. The results indicate that the stability of Ln2+ in strontium borates depends on the nature of the borate anions surrounding it and the effectiveness of the compensation of the charge on Ln3+, which can be quantified by the formal volume per oxygen atom, VO, in the structure of the borate.

Luminescence characteristics of the Pr3+ ion in SrB4O7 and SrB6O10

Spectral and kinetic characteristics of the luminescence and luminescence excitation spectra of polycrystalline SrB4O7:Pr (1%) and SrB6O10:Pr (1%) samples are studied at 150–170 K. The samples show an intense luminescence band in the vicinity of 405 nm (1S0→1I6 transitions of Pr3+) and shorter wavelength bands also assigned to transitions from the 1S0 level. The main luminescence decay constant is ∼2×10−7 s. The excitation spectra of the 1S0 luminescence in these crystals are significantly different. The SrB4O7:Pr crystal shows three well-resolved bands at 6.14, 6.55, and 6.91 eV in the region of the 4f2→4f15d transitions and a complex structure in the region of interband transitions (7.1–20 eV), whereas the SrB6O10:Pr crystal shows a weakly structured band at 6.31 eV and no excitation in the region of the interband transitions. The physical mechanisms that may be responsible for the observed features of the spectra are discussed.

Luminescence of calcium orthoborate doped by Ce3+ ions

The luminescence properties of calcium orthoborate Ca3(BO3)2 doped with cerium are studied upon x-ray (∼30 keV) and VUV (3.5–15 eV) synchrotron excitation. The emission bands peaked at 392 and 420 nm are attributed to interconfigurational transitions of Ce3+ ions. The short-wavelength emission band at 340 nm is caused by radiative decay of exciton-like states. The fundamental absorption edge of Ca3(BO3)2 is found to be near 7.1 eV. Based on thermoluminescence data and other information, the behavior of defects in Ca3(BO3)2:Ce3+ is studied.

Effect of Eu 2 O 3 Doping on the Crystallization Behavior of BaO-Bi 2 O 3 -B 2 O 3 Glasses

We gave studied the crystallization behavior of 30BaO · 25Bi2O3 · 45B2O3 glasses doped with Eu2O3 to different levels. At a Eu2O3 content of 7 mol % or higher, the glasses undergo volume crystallization. The only precipitating phase is a solid solution between europium and bismuth oxides. With increasing europium concentration in the glass, the structure of the crystallites changes from cubic to rhombohedral. We have investigated the morphology, physicochemical properties, and luminescence spectra of the glasses and glass-ceramics.

Luminescent properties and stability of europium ions in Ca2BO3Cl:Eu

We have studied the luminescent properties of Eu2+ and Eu3+ in the calcium chloride borate Ca2BO3Cl under optical and synchrotron excitation. The results demonstrate that a reductant should be present during synthesis in order to stabilize Eu2+ in Ca2BO3Cl and provide insight into the factors responsible for the long-wavelength position of the luminescence band (λmax = 577 nm) and the relatively low Eu2+ stability in Ca2BO3Cl.

Luminescence of Yb3+ ions in calcium tetraborate with charge transfer

The luminescent properties of Yb3+ ions in calcium tetraborate CaB4O7 under x-ray (∼30kV) and UV (3.5–15 eV) excitations are studied. Apart from the IR luminescence associated with the 2F5/2→2F7/2 transitions occurring in the Yb3+ ions, the x-ray excitation of CaB4O7:Yb3+ at room temperature gives rise to a broadband luminescence at 330 nm with a large Stokes shift and a decay time of ∼30 ns. On the basis of analysis of the experimental results and their comparison with data from the literature, it is shown that this broadband luminescence is caused by radiative decay of charge transfer states of the Yb3+ ions.