The design and preparation of the thermally stable, Mn4+ ion activated, narrow band, red emitting fluoride Na3GaF6: Mn4+ for warm WLED applications

Herein, a new red phosphor Na3GaF6: Mn4+ has been designed and synthesized by a facile two-step co-precipitation method at room temperature. Single crystal X-ray diffraction analysis reveals that the fluoride Na3GaF6 crystallizes in the P2(1)/n space group with a = 5.4760 angstrom, b = 5.6862 angstrom, c = 7.9009 angstrom, beta = 90.3091 degrees, and z = 2. Upon blue or UV light excitation, the obtained phosphor Na3GaF6: Mn4+ emits intense and pure red fluorescence. The effects of raw materials, doping concentration and environmental temperature on its luminescence properties and crystal structure have been investigated and discussed in detail. Such a newly synthesized red phosphor shows excellent anti-thermal quenching behavior (similar to 118.8% of emission intensity at 150 degrees C relative to 25 degrees C) and good color stability upon blue light (similar to 467 nm) excitation. By using the Na3GaF6: Mn4+ phosphor as a red light component, a highpower stable warm white light-emitting diode (WLED, R-a = 81, CCT = 2966 K, luminous efficacy = 56.73 lm W-1) was fabricated, further evidencing the potential of the as-synthesized Na3GaF6: Mn4+ phosphor for white LED applications.