Enhancement of luminescence and thermal stability of NaLi3SiO4: Eu phosphor by co-doping K+ ions.

High-efficiency phosphor with excellent luminescence properties and thermal stabilities is essential for phosphor-converted white light-emitting diodes (w-LEDs). Compared with red and green phosphors, near-ultraviolet excited blue phosphors with high efficiency and excellent thermal stability are still scarce, and the development of efficient blue phosphors remains challenging. NaLi 3 SiO 4 : Eu2+ (NLSO: Eu2+) is a promising narrow-band blue phosphor. In this paper, a series of Na 1-y K y Li 3 SiO 4 : 5%Eu2+ (0.05 ≤ y ≤ 0.2) phosphors were successfully synthesized by high-temperature solid-state reaction through co-doping a small amount of K+ ions in the matrix, significantly improving their luminescence property and thermal stability. Because of the weaker electronegativity of K+ ions, the emission peaks of Na 1-y K y Li 3 SiO 4 : 5%Eu2+ were slightly blue-shifted from 467 to 463 nm compared with those of NLSO: Eu2+. With an increase in the number of K+ ions, the luminescence intensity of the phosphors increased. When the content of the K+ ion reached 0.2, the luminescence intensity of the Na 0.8 K 0.2 Li 3 SiO 4 : 5%Eu2+ (NKLSO: 5%Eu2+) phosphor reached its maximum. Compared to the NLSO: 5%Eu2+ phosphor, the luminescence intensity increased by approximately 300 %. At 150 °C, the luminescence intensity of NLSO: 5%Eu2+ phosphor was retained at 75.98 % compared with room temperature, while the NKLSO: 5%Eu2+ phosphor maintained a luminescence intensity of 84.36 % relative to room temperature, demonstrating excellent thermal stability. The enhanced luminescence performance of the NKLSO: Eu2+ phosphor makes it a promising high-efficiency blue phosphor for phosphor-converted w-LEDs. Through co-doping a small amount of K+ ions into the NaLi 3 SiO 4 : Eu2+, significantly improving the luminescence property and thermal stability. [Display omitted] • A series of Na 1-y K y Li 3 SiO 4 : 5%Eu2+ (0.05 ≤ y ≤ 0.2) phosphors were successfully synthesized through co-doping K+ ions in the matrix. The weaker electronegativity of K+ ions makes it easier for Eu3+ to be reduced to Eu2+. • In luminescence properties, when the content of the K+ ion reached 0.2, the luminescence intensity of the Na 0.8 K 0.2 Li 3 SiO 4 : 5%Eu2+ phosphor reached its maximum. Compared to the NaLi 3 SiO 4 : 5%Eu2+ phosphor, the luminescence intensity increased by approximately 300 %. • The Na 0.8 K 0.2 Li 3 SiO 4 : 5%Eu2+ exhibited superior thermal stability compared to NaLi 3 SiO 4 : 5%Eu2+. The luminescent intensity of NaLi 3 SiO 4 : 5%Eu2+ at 150 °C remains 75.98 % of the room temperature intensity, while the luminescent intensity of Na 0.8 K 0.2 Li 3 SiO 4 : 5%Eu2+ is significantly increased to 84.36 %. • The narrowband blue phosphor Na 0.8 K 0.2 Li 3 SiO 4 : 5%Eu2+ is a potential candidate for n-UV excited w-LEDs applications because of its excellent luminescence properties. [ABSTRACT FROM AUTHOR]