Optical spectroscopy of lanthanide ions in ZnO–TeO2 glasses

Abstract

Zinc tellurite glasses of compositions 19ZnO-80TeO 2 -1Ln 2 O 3 with Ln= Eu, Er, Nd and Tm were prepared by melt quenching. The absorption spectra were measured and from the experimental oscillator strengths of the f f transitions the Judd-Ofelt parameters V u were obtained. The values of the V u parameters are in the range usually observed for oxide glasses. For Nd 3 + and Er 3 + , luminescence spectra in the near infrared were measured and the stimulated emission cross sections | p were evaluated for some laser transitions. The high values of | p , especially for Nd 3 + , make them possible candidates for optical applications. Fluorescence line narrowing (FLN) spectra of the Eu 3 + doped glass were measured at 20 K, and the energies of the Stark components of the 7 F 1 and 7 F 2 states were obtained. A crystal field analysis was carried out assuming a C 26 site symmetry. The behaviour of the crystal field ratios B 22 /B 20 and B 44 /B 40 agrees reasonably well with the values calculated using the geometric model proposed by Brecher and Riseberg. The crystal field strength at the Eu 3 + sites appears to be very low compared to other oxide glasses.

Effect of lithium addition on thermal and optical properties of zinc–tellurite glass

“…It was found that the building units of these glasses are TeO 4 , TeO 3+1 and TeO 3 groups. The four oxygens in the TeO 4 are located at four vertices of a trigonal bipyramid and TeO 3+1 groups are similar to TeO 4 but with a long Te-O bond while TeO 3 groups in which one of the Te sp3 hybrid orbitals is occupied by lne pair of electrons, where the oxygens are arranged at three vertices of a tetrahedron [4,11]. In addition, the glass formation in TeO 2 -ZnO binary system strongly depends on the cooling rate and the size of the melt, especially in the TeO 2 -rich region [3].…”

The local structure of gadolinium vanadate–tellurate glasses and glass ceramics: Te2V2O9 crystalline phase

“…It is very difficult to form pure vitreous TeO 2 and it has been suggested [3] that this is due to the lone pair of electrons in one of the equatorial positions of the [TeO 4 ] polyhedron. The repulsive forces in this zone hinder the free movement of the polyhedra in space during the cooling of the melt.…”

Morphology-dependent upconversion luminescence of ZnO:Er3+ nanocrystals

“…The luminescence quantum yield of ZnO:Er is, in general, less than 5% for the green and the red emissions. These values are short compared to that of the Er 3+ doped in similar bulk materials [33,34]. The lengthening of the decay and the increase of the estimated quantum yield in samples 5 and 6, compared with the rest samples, reveal that the luminescence quenching is less for the two, probably indicating that in these two samples more Er 3+ ions were doped into the internal area of ZnO, different from the rest samples where majority of Er 3+ ions were within the surface layer, if not all of them.…”