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

Abstract

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 Å, b = 5.6862 Å, c = 7.9009 Å, β = 90.309°, 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 (∼118.8% of emission intensity at 150 °C relative to 25 °C) and good color stability upon blue light (∼467 nm) excitation. By using the Na₃GaF₆:Mn⁴⁺ phosphor as a red light component, a high-power 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.