Structural and optical study of glasses in the TeO2-GeO2-PbF2 ternary system

New glass compositions were investigated in this specific proportion (90-x)TeO2-10GeO2-xPbF2 in order to study the influence of lead fluoride content on the thermal, structural and optical properties. Glass samples with x = 5 to 30% were prepared by melt-quenching method. Thermal characterizations by DSC allowed to identify a clear decrease of the glass transition temperature as well as a very distinct crystallization behavior for higher PbF2 contents. Raman spectroscopy suggests a progressive PbF2 incorporation with conversion of TeO4 to TeO3 units related with the modifier behavior of PbF2 in the glass network. X-ray diffraction patterns of crystallized samples support these results since crystalline TeO2 was detected for lower PbF2 contents whereas lead tellurite Pb2Te3O7 was identified for the most lead fluoride concentrated sample. UV-Vis-NIR absorption spectra are in agreement with a progressive increase of the optical bandgap with lead fluoride concentration. Emission spectra of Eu3 + doped samples also pointed out a progressive structural change around Eu3 + ions with more symmetric sites. Finally, experimental lifetimes, Judd-Ofelt parameters and quantum efficiencies were obtained from these samples and exhibited a strong dependency of the lead fluoride contents, suggesting that these new fluorotellurite glasses are interesting hosts for rare earth ions.