Structural and optical characterization of the local environment of Er 3+ ions in PbO–ZnO tellurite glasses

Erbium activated PbO-ZnO tellurite glasses ((70TeO2-(30-x)ZnO- xPbO)0.99-(Er2O3)0.01 (TZPE), (x = 5, 10, 15, 20)) were prepared by a melt quenching process and studied by optical absorption, luminescence, Raman and x-ray absorption spectroscopy measurements as a function of the PbO/ZnO ratio. The glass structure, as monitored by Raman scattering, shows important changes with the PbO/ZnO ratio, attributed to a glass former action of PbO. The local environment of Er3+ ions, as measured by extended x-ray absorption spectroscopy, does not appreciably change as regards the first oxygen shell. However, the intensity of the optical transitions is quite sensitive to the PbO/ZnO ratio, indicating a progressive increase of the site symmetry with the PbO content. The emission probability and radiative lifetime of several excited states of Er3+ ions were calculated using Judd-Ofelt analysis.