Control of Luminescence by Tuning of Crystal Symmetry and Local Structure in Mn 4+ -Activated Narrow Band Fluoride Phosphors.

Mn ⁴⁺ -doped fluoride phosphors have been widely used in wide-gamut backlighting devices because of their extremely narrow emission band. Solid solutions of Na ₂ (Si _x Ge _1-x )F ₆ :Mn ⁴⁺ and Na ₂ (Ge _y Ti _1-y )F ₆ :Mn ⁴⁺ were successfully synthesized to elucidate the behavior of the zero-phonon line (ZPL) in different structures. The ratio between ZPL and the highest emission intensity υ ₆ phonon sideband exhibits a strong relationship with luminescent decay rate. First-principles calculations are conducted to model the variation in the structural and electronic properties of the prepared solid solutions as a function of the composition. To compensate for the limitations of the Rietveld refinement, electron paramagnetic resonance and high-resolution steady-state emission spectra are used to confirm the diverse local environment for Mn ⁴⁺ in the structure. Finally, the spectral luminous efficacy of radiation (LER) is used to reveal the important role of ZPL in practical applications.
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