Local structure and optical-luminescent properties of the Pb-containing germanate and silicate oxygen-fluoride glasses

The XRD, IR transmission, EPR, optical absorption, photoluminescence and its decay kinetics in the un-doped Pb-containing germanate and silicate oxygen-fluoride glasses with compositions of 0.5PbO–0.3GeO 2 –0.2AlF 3 and 0.53PbO–0.226SiO 2 –0.244AlF 3 were investigated and analysed. Average interatomic distances and coordination numbers for main structural units GeO 4 , SiO 4 , and PbO n (n = 3 – 6) as well as Pb-Pb, Pb-Al, Pb-Ge, and Pb-Si interatomic distances in the network of studied glasses were defined from their radial distribution functions. The IR transmission, EPR, UV-Vis absorption spectra of the studied glasses were registered and interpreted. Optical band gap and Urbach energy for both studied glasses have been evaluated from fundamental absorption edge analysis. The 0.5PbO–0.3GeO 2 –0.2AlF 3 and 0.53PbO–0.226SiO 2 –0.244AlF 3 glasses upon UV photoexcitation demonstrate intense broad emission bands with maxima at 493 and 499 nm, respectively. Based on luminescence decay kinetics analysis of the observed emission bands were proposed fast (band-to-band recombination) and slow (recombination with participation of point defects levels) mechanisms of intrinsic luminescence in the studied glasses. The CIE chromacity diagram shows variation of emission colour of the studied glasses with change of their composition.