Judd–Ofelt analysis and radiative properties of LiLa(1−x)Eux(PO3)4

Abstract

Judd–Ofelt (J–O) theory has been applied to a series of LiLa1−xEux(PO3)4 (x=5%; 10%; 15%; 20% and 30%) polycrystalline powders based on their emission spectra. J–O intensity parameters Ωλ (λ=2, 4) and various radiative properties such as the radiative transition probability (A), radiative life time (τR), branching ratio (βR) and stimulated emission cross-section (σe) have been determined. The observed trend for J–O parameters (Ω2<Ω4) reveals the ionic character of La(Eu)–O bond as well as the symmetry environment around the Eu3+ ion in LiLa(PO3)4. The experimental decay curves of the 5D0 level in LiLa1−xEux(PO3)4 have a single exponential profile. The registered long life time, low multiphonon relaxation rates (WNR), high quantum efficiency (η) and the best optical gain parameter (σexτexp) have been discussed as function of Eu3+ concentration, chemical composition and crystal structure of the host matrix and particle-size distribution. A comparative study reveals that LiLa1−xEux(PO3)4 is promising for use in optical devices as well as for developing visible red lasers to emit at 613nm. The optical band gap energies of LiLa1−xEux(PO3)4 have been calculated from the diffuse reflection spectral measurements. The results were discussed as a function of Eu3+ concentration and compared to reported theoretical results.