Ammonium salt conversion towards Mn4+ doped (NH4)2NaScF6 narrow-band red-emitting phosphor

Mn 4+ -activated fluoride red phosphors have a bright prospect for improving the warm white light-emitting diodes (W-LEDs) performances, whereas there remains some challenges in synthesis, such as reducing the consumption of toxic HF and improving Mn 4+ doping efficiency. Herein, a new phosphor (NH 4 ) 2 NaScF 6 :Mn 4+ (NNSFM) was synthesized by an ammonium salt conversion method, which can effectively reduce HF consuming, enhance reaction rate and doping efficiency. The synthesis mechanism, luminescence properties and W-LEDs performances of the as-synthesized NNSFM have been investigated. Moreover, the lattice structure and doping position have been investigated in detail by the density functional calculations (DFT), which show that Mn 4+ could occupy the Sc 3+ crystallographic site in this structure and simultaneously produce a Na vacancy ( V Na ' ${\text{V}}_{\text{Na}}^{\text{'}}$ ) for charge compensation. Using the NNSFM as red-light component, a warm W-LED device with a high color rendering index (CRI, Ra = 80.6) and low correlated color temperature (CCT = 3006 K) has been achieved. This work presents a new Mn 4+ doped fluoride red phosphor and also develops an environmentally friendly strategy for synthesizing Mn 4+ doped fluoride phosphors.