Li ₂ La ₈ Si ₆ N ₁₂ O ₇ : A Promising Oxonitridosilicate Host for Pr ³⁺ and Tb ³⁺ Activated Phosphors Grown in Li ₃ N Flux

A novel oxonitridosilicate, Li2La8Si6N12O7 was successfully synthesized at 1200 °C using Li3N as a flux. The crystal structure was determined through single-crystal and synchrotron powder X-ray diffraction. Li2La8Si6N12O7 crystallizes in orthorhombic space group Pcca (no. 54) with unit-cell parameters a = 15.5319(1) Å, b = 7.7382(1) Å, c = 15.5019(1) Å, and Z = 4. The structure features a layered framework built from vertex-sharing Si[N/O]4 tetrahedra, with Li[N/O]6 octahedra connecting and stabilizing both the interlayer and intralayer linkages. The octahedral coordination of Li+ was confirmed by solid-state 7Li NMR spectroscopy. Notably, the incorporation of Pr3+ and Tb3+ into the Li2La8Si6N12O7 host yields narrow-band red emission at 630 nm and green emission at 545 nm. This combination facilitates the fabrication of 365 nm near-ultraviolet light-emitting diode (UV LED) chip-based WLEDs with superior color rendering performance.