Sr₂BN₂Cl:Eu²⁺-Based Narrow-Band Blue-Emitting Phosphor: A Potential Color Converter for Illumination and Displays

Due to the wide range of uses for phosphors in lighting and displays, research on narrow-band luminescent phosphors has recently received significant interest. In this work, Eu²⁺-activated Sr₂BN₂Cl phosphor has been successfully synthesized. Sr₂BN₂Cl:Eu²⁺ shows a wide absorption band in the UV region and exhibits a narrow-band emission peaking at 450 nm with a full width at half-maximum of ∼60 nm. More significantly, excellent thermal stability was discovered, which showed it still retained 87.4 and 100% of room-temperature intensity at 150 and 250 °C, respectively. The rigid skeleton formed by the co-edge connection of Sr(N, Cl)₆ octahedra and defects in the crystal are responsible for the excellent thermal stability of the phosphor. In addition, two types of white-led devices have been prepared to test this phosphor for illumination and display applications. The former shows low correlated color temperature (CCT = 3190 K) and a high color rendering index (CRI = 92.0). The latter shows that using Sr₂BN₂Cl:Eu²⁺, β-sialon:Eu²⁺, and K₂SiF₆:Mn⁴⁺ together for backlit displays can cover 73.3% of the NTSC area, which is comparable to commercial BaMgAl₁₀O₁₇:Eu²⁺ phosphors. These findings suggest that the blue phosphor Sr₂BN₂Cl:Eu²⁺ will be a promising choice for lighting and backlight displays.