Theoretical and Experimental Investigation on Structural, Elastic, Electronic, and Optical Properties of Ni 2+ -Activated Double Perovskite Sr 2 MgMoO 6

In this study, a comprehensive investigation of the properties of Ni 2+ -doped Sr 2 MgMoO 6 was carried out through a combination of theoretical calculations and experimental characterization. The dynamical and mechanical stabilities of the Sr 2 MgMoO 6 host were accessed by calculating a set of elastic constants and Debye temperatures, which confirms its structural stability and rigidity for the incorporation of the Ni 2+ -emitting center. It was found from DFT formation energy calculations that Mg 2+ is the most energetically favorable for Ni 2+ incorporation among the available cation sites. The calculated geometric results of Ni 2+ ground and excited levels agree with experimental excitation and emission bands, which are mainly assigned from the 3d–3d transitions of Ni 2+ located in the octahedral site. The as-obtained Sr 2 MgMoO 6:Ni 2+ exhibits a strong NIR-II broadband emission centered around 1415 nm, resulting from the Ni 2+3 T 2 → 3 A 2 transition. An NIR-II LED prototype by combining the Sr 2 MgMoO 6:Ni 2+ phosphor with a blue chip as the lighting source for noninvasive decryption and detection is demonstrated. The yellow body colors of Sr 2 Mg 1– x Ni x MoO 6 (0 ≤ x ≤ 0.4) compounds deepen as the Ni content increases. The plastic composites with desirable color are successfully fabricated using Sr 2 MgMoO 6:Ni 2+ and PMMA. This work offers a perspective on the structure–property relationship in Ni 2+ -doped double perovskite.