Judd-Ofelt analysis of spectroscopic properties of Eu3+ doped KLa(PO3)4

Based on Judd-Ofelt (J-O) theory, the intensity parameters (Ω2 and Ω4) have been evaluated from the emission spectra of KLa(1−x)Eux(PO3)4 (where x=2, 5, 10, 15, 20 and 30 mol%) polycrystalline powders as a function of Eu3+ ion concentration. The registered trend (Ω2<Ω4) reveals the ionic character of the La(Eu)-O bonds as well as a relatively high symmetry environment around the rare earth ion (RE) site in KLa(PO3)4 as compared to other host matrix. From these intensity parameters various radiative properties like spontaneous emission probability (A), branching ratio (βR), stimulated emission cross-section (σ) and the radiative lifetime (τR) have been calculated. The decay profiles for the 5D0 excited level of Eu3+ in KLa(PO3)4 have been found to be single exponential and independent of Eu3+ ion concentration even at 30 mol%. In comparison with other Eu3+-doped materials, KLa(PO3)4:Eu3+ has a long lifetime, low multiphonon relaxation rates (WNR), high quantum efficiency (η) and better optical gain parameter (σxτexp). The determined radiative properties reveal the usefulness of KLa(1−x)Eux(PO3)4 in developing visible red lasers as well as optical display devices at around 613 nm. Our results were discussed as a function of Eu3+ concentration, crystal structure of KLa(PO3)4 and particle-size distributions.