A comparison of spectroscopic properties of Dy3+-doped tetragonal tungsten bronze MTa2O6 (M = Sr, Ba, Pb) phosphors based on Judd-Ofelt parameters

TTB (tetragonal tungsten bronze) crystal structures exhibit very interesting physical properties as well as the superiority of having different cationic sites and allowing doping. In the study, the spectroscopic results of TTB-MTa2O6:Dy3+ (M = Sr, Ba, Pb) phosphors are presented using Judd-Ofelt (JO) intensity parameters. The PL and RL spectra of the phosphors exhibited the characteristic emissions of Dy in the visible and infrared regions. The PL excitation spectra were used to determine JO parameters (omega(2), omega(4), omega(6)). The decreasing trend of omega(2) parameter and PL asymmetry is SrTa2O6:Dy3+ > PbTa2O6:Dy3+ > BaTa2O6:Dy3+, which shows low electronegativity and shifting to the long wavelength of BaTa2O6:Dy3+ supports the low value of the omega(2) parameter and covalence. The PL decay profiles of all the phosphors are double exponential and the fast decreasing of PL decay components of SrTa2O6:Dy3+ is compatible with the concentration quenching after 5 mol%. The decreasing trend of the observed lifetime is in order BaTa2O6:Dy3+ > PbTa2O6:Dy3+ > SrTa2O6:Dy3+, which can be attributed to the defect centers depending on the increase of the covalency.