Copper nanoparticles enhanced luminescence of Eu3+ doped lead tellurite glass ceramics

Structural, optical and magnetic properties of some lead tellurite glass ceramics doped with europium(III) ions and co-doped with fixed amounts of metallic copper nanoparticles (CuNPs) or copper(II) ions (via CuO) were investigated. Samples in the (Eu2O3)(x)center dot(TeO2)(80)center dot(PbO)((19.7-x))center dot(CuNPs)(0.3) and (Eu2O3)(x)center dot(TeO2)(80)center dot(PbO)((19.7-x))center dot(CUO)(0.3) systems with 0 <= x <= 10 mol% were obtained and investigated for the first time. Several techniques such as X-ray diffraction, UV-VIS, EPR and luminescence spectroscopies and density and magnetic susceptibility measurements were used in order to characterize the samples. XRD data show that the samples with low Eu2O3 contents (x <= 1 mol%) are amorphous while for higher europium oxide contents (x > 1 mol%) are glass ceramics. They also reveal that increasing the Eu2O3 content of samples the symmetry around the europium ions changes from face centered cubic to monoclinic. These symmetry changes are confirmed by the photoluminescence data. In addition, photoluminescence data show that the co-doping with metallic copper nano particles enhances the emission peaks of europium ions. UV-VIS absorption spectra show the presence of six coordinated copper (II) ions located at sites with a distorted octahedral symmetry. The EPR data confirm the presence of copper (II) ions in all the studied samples. Magnetic susceptibility measurements suggest the presence of europium ions in both their 3+ and 2+ valence states and evidence an important clustering tendency of europium ions even for low Eu2O3 contents.