Investigation into the great enhancement of luminescence intensity through K/Na substitution in Nepheline structure for WLED

Eu²⁺-activated silicate phosphors have excellent properties such as high quantum efficiency, good thermal stability, and tunable emission spectrum. Until now, the unclear physical mechanism of the increase in Eu²⁺ quantum efficiency due to equivalent cation doping still puzzles us. In this paper, K_1+yNa_3-yAl₄Si₄O₁₆:6% Eu²⁺ (0 ≤ y ≤ 0.8) series phosphors with dazzling green light emission are successfully prepared by the high-temperature sintering method, and the emission intensity is enhanced by changing the ratio value of K/Na in the matrix material. Three models are proposed to verify the exact reasons that cause the enhanced intensity by equivalent cation doping. Through Gaussian fitting, XPS, thermoluminescence, and pressure-dependent PL analysis, it has been confirmed that the decrease in interaction between Eu²⁺ ions, as well as the different electronegativity between Na and K, are the primary factors contributing to the enhancement of luminescence. In final, by adjusting the K/Na ratio, the emission spectrum intensity increases by 1.53 times, and the quantum efficiency rises by almost 22%. Using the efficient green-emitting phosphor, along with BAM: Eu²⁺ and CaAlSiN₃:Eu²⁺, efficient full-spectrum emission with a high CRI index, strong electroluminescent power, and optimal color temperature is obtained. Meanwhile, this research to improve the luminescence intensity also provides a new design idea for the equivalent substitution of other Eu²⁺-activated silicate photoluminescence materials, which can be utilized in the solid lighting field.