Crystal structures and luminescence properties of Ca₃RE₂Si₄O₈N₄ (RE = Y, La, and Ce) activated by Ce³⁺

The discovery of new compounds expands the scope of materials chemistry. In this study, we report a new series of oxynitride compounds, Ca₃RE₂Si₄O₈N₄ (RE = Y, La, and Ce), and their crystal structures. The samples were synthesized by a solid-state reaction method under an inert atmosphere. Single-crystal X-ray diffraction analysis revealed that these compounds are isostructural and crystallize in the cubic space group Pa3̄. The structures contain four crystallographically distinct cation sites and unique isolated 12-membered ring units constructed from Si(O,N)₄ tetrahedra. Ce³⁺-containing samples exhibit broad photoluminescence under ultraviolet excitation, and the emission colour changes from deep blue to bluish green with varying RE composition. Analysis of the emission spectra suggests that the luminescence originates from multiple crystallographic sites and exhibits thermal quenching behaviour. These results demonstrate that Ca₃RE₂Si₄O₈N₄ represents a new class of oxynitride phosphors with multi-site luminescence and tuneable emission properties.