Abstract
<jats:p>The Judd–Ofelt theory governs the intensity of 4fn ↔ 4fn transitions of rare earth ions in terms of an admixed induced electric dipolar character from higher energetic even parity states by the crystal field and successfully reproduces experimental absorption and emission line strengths. Traditionally, the Judd–Ofelt theory requires three intensity parameters that have to be estimated from an experimental absorption spectrum. That approach is fundamentally problematic with non-transparent or polycrystalline materials, and particularly with Pr3+ ions due to the low energy difference between the excited 4f15d1 configuration and the 4f2 spin–orbit levels, which is in contrast with the closure approximation necessary for the validity of the Judd–Ofelt theory and usually leads to non-physical intensity parameters. In this work, an algorithm based on experimental emission spectra is presented that resolves these limitations. For that purpose, steady-state and time-resolved emission spectra at liquid nitrogen temperatures (T = 77 K) as well as decay times of the 1D2 and 3P0 levels were measured. The method was tested on hydrothermally prepared Sr2LaF7:Pr3+ as a representative example as this compound shows emission from both the 3P1,0 and 1D2 levels at room temperature with measured decay times of the 3P0 and 1D2 level of 59 and 225 μs, respectively. From the intensities of the 3P0 → 3H4,6, 3F2-based emission, and the 1D2-based decay time, Judd–Ofelt parameters of Ω2 = 2.34 × 10−20, Ω4 = 5.84 × 10−20, and Ω6 = 21.68 × 10−20 cm2 were obtained. The calculated values showed very good agreement with the diffuse reflectance measurements and allowed the prediction of Pr3+ near infrared emission intensities.</jats:p>