Synthesis and Photoluminescence Properties of Ca₂Ga₂SiO₇:Eu³⁺ Red Phosphors with an Intense ⁵D₀ → ⁷F₄ Transition

Novel melilite-type Ca₂Ga₂SiO₇:Eu³⁺ red-emitting phosphors with different Eu³⁺ contents were synthesized via high-temperature solid-state reaction. The crystal structure, optical absorption, and photoluminescence properties were investigated, while density functional theory calculations were performed on the host lattice. The excitation spectra indicate that phosphors can be effectively excited by near-UV light for a potential application in white-light-emitting diodes. Because of the abnormally high intensity emission at about 700 nm arising from the ⁵D₀ → ⁷F₄ transition of Eu³⁺, the phosphors Ca₂Ga₂SiO₇:Eu³⁺ show a deep-red emission with chromaticity coordinates (0.639, 0.358)