Evolution of Structure and Photoluminescence by Cation Cosubstitution in Eu²⁺-Doped (Ca_1–<i>x</i>Li_<i>x</i>)(Al_1–<i>x</i>Si_1+x)N₃ Solid Solutions

Abstract

Red-emitting nitride phosphors excited with blue light have great potential for the fabrication of warm white light-emitting diodes (WLEDs). Chemical composition and structural modification are generally adopted to optimize the photoluminescence behaviors of the targeted phosphors. Herein, on the basis of the famous CaAlSiN3 phosphors, Eu(2+)-doped (Ca(1-x)Li(x))(Al(1-x)Si(1+x))N3 solid solutions via the cations' cosubstitution of (CaAl)(5+) pair by (LiSi)(5+) pair are successfully synthesized by a solid state reaction, and the lattice parameters show a linear decrease with chemical compositions suggesting the formation of the isostructural phase relationship. Four types of coordinated structure models, corresponding to different coordination environments of Eu(2+), are proposed over the course of structural evolution, which induces different structural rigidity and stability, and then they are responsible for three-stage changes of emission spectra of Eu(2+) in (Ca(1-x)Li(x))(Al(1-x)Si(1+x))N3 solid solution.