Papers by Author: E. Antić-Fidančev

Abstract: In view of the improvement of luminescent intensity in classical phosphors, different new techniques of synthesis have been developed. One of them is the sol-gel technique for nanopowder synthesis. Applied to a binary system Gd2O3-SiO2 doped with trivalent europium ion, very fine powder form samples have been obtained. In that case the emission intensity of 5D0→F2 electronic transition of 4f6 configuration is greatly enhanced compared to the bulk oxide. The lifetime measurements are given too. The size of nanoparticles is of about 10 nm, determined by dynamic light scattering and XRD analysis.

Abstract: Tungsten-phosphate glasses doped with trivalent europium ion are synthesized and their spectroscopic properties are analyzed. Following the evolution of the 5D0 → 7F1 electronic transition in a series of various glass compositions via two rank crystal field parameters (cfp’s), a slight modification of the local symmetry is evidenced in the series. Decay lifetimes of 5D1 and 5D0 levels are also analyzed. Optical properties clearly correspond to Eu3+ in the glassy phase. At room as well as at liquid nitrogen temperatures, the emission spectra display comparable features with prominent 5D0 → 7F2 transition. However, at 77 K, the maximum 7F1 splitting exhibits an increase of ≈ 20-23 % for all compounds. This increase is directly connected to a change in local environment around the rare earth ion. The optical properties and the crystal field variation could be correlated with the shortness of the metal-oxygen distances produced by the pressure when cooling.

Abstract: Complex emission spectra of europium doped rare earth calcium oxoborates, EuCa4O(BO3)3 - EuCOB, and GdCa4O(BO3)3: Eu3+- GdCOB: Eu3+, were finely analyzed for better understanding of some local perturbations detected in these solid media. Highlighting a “size effect” of dopant / matrix ions, the interaction between the host lattice and the embedded ion is demonstrated. The evolution of the crystal field strength of R3+ ions along the rare earth series is presented for C-type RE2O3 oxides. According to R3+ - RE3+ ionic radii difference (R3+ for a dopant ion and RE3+ for a matrix ion), two opposite standings are evidenced along a series. Effect of high concentration doping on spectral line broadening is illustrated following a half-height width of 2P1/2 level of Nd3+ ion in A-type La2O3 oxide.