Design of a nitridoalumosilicate red phosphor synthesized under mild conditions

Abstract

Developing nitridosilicate red phosphors under mild synthesis conditions is important for regulating the emission quality of white light-emitting diodes (WLEDs). Based on the thermodynamic theory and crystal structure chemistry for the synthesis of nitridosilicates, the Gibbs free energy variation of a hybrid system can be made more negative by reducing the proportion of Si₃N₄ and increasing the proportion of M₂N₃ and AlN, enabling the formation of new nitridosilicates under mild conditions. Therefore, a general chemical formula M_xSi_yAl_zN_k was proposed for the design of nitridosilicate red phosphors prepared under mild conditions, where M is an alkaline earth metal ion; x > y; z ≥ y; 1 ≤ y ≤ 3; x + 2y = 3n + 3; k − z = 2n + 2; and n is a positive integer. Therefore, in this study, we successfully synthesized the nitridoalumosilicate red phosphor Ca₄SiAl₃N₇:Eu²⁺ at normal pressure and lower temperature (1350 °C). Under excitation with 460 nm blue light, the Ca₄SiAl₃N₇:Eu²⁺ phosphor efficiently emits red light at 645 nm and exhibits excellent thermal stability. The crystal structure and luminescence properties of Ca₄SiAl₃N₇:Eu²⁺ were investigated in detail. The results indicate that Ca₄SiAl₃N₇:Eu²⁺ exhibits strong potential for use in WLEDs. The design of nitridoalumosilicate red phosphors synthesized under mild conditions based on Gibbs free energy variation provides a new idea for the development of new nitride phosphors.