Analytical disquisition on the Judd-Ofelt parameters and the temperature sensing properties of Sm³⁺ doped aluminate phosphors

In the present study, Sm³⁺ (0.5, 1.0, 1.5, 2.0, and 2.5 mol%) doped SrAl₂O₄ phosphors were synthesized via the solid-state reaction technique, and the Judd-Ofelt (JO) parameters were evaluated using emission spectral data. Structural analysis combined with Rietveld refinement confirmed the phase purity of the host lattice with only a trace presence of secondary phases. Optical studies revealed a strong dependence of emission intensity on Sm³⁺ concentration, with optimal luminescence observed at 1.5 mol%. The corresponding chromaticity coordinates indicate emission in the light reddish-orange region. Furthermore, the temperature-dependent luminescence (TDPL) characteristics of the optimized phosphor were systematically investigated in the 273–498 K range under UV excitation of 401 nm. The emission intensity revealed anomalous thermal behaviour, attributed to the presence of intrinsic lattice defects. The optimized composition retained 90.29% of its room-temperature emission intensity with an activation energy of 0.18 eV. To assess the thermometric performance, the fluorescence intensity ratio was analyzed using 2nd and 3rd order polynomial fitting models. The maximum absolute sensitivities were found to be 0.0004 K⁻¹ and 0.0003 K⁻¹, while the corresponding relative sensitivities reached 0.077% K⁻¹ and 0.066% K⁻¹, respectively.