Design of a nitridoalumosilicate red phosphor synthesized under mild conditions.

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 Si ₃ N ₄ and increasing the proportion of M ₂ N ₃ and AlN, enabling the formation of new nitridosilicates under mild conditions. Therefore, a general chemical formula M _x Si _y Al _z N _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 + 2 y = 3 n + 3; k - z = 2 n + 2; and n is a positive integer. Therefore, in this study, we successfully synthesized the nitridoalumosilicate red phosphor Ca ₄ SiAl ₃ N ₇ :Eu ²⁺ at normal pressure and lower temperature (1350 °C). Under excitation with 460 nm blue light, the Ca ₄ SiAl ₃ N ₇ :Eu ²⁺ phosphor efficiently emits red light at 645 nm and exhibits excellent thermal stability. The crystal structure and luminescence properties of Ca ₄ SiAl ₃ N ₇ :Eu ²⁺ were investigated in detail. The results indicate that Ca ₄ SiAl ₃ N ₇ :Eu ²⁺ 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.