Li24Sr12[Si24N47O]F:Eu2+Structure and Luminescence of an Orange Phosphor

The oxonitridosilicate fluoride phosphor Li24Sr12[Si24N47O]­F:Eu2+ was synthesized from Si3N4, SrH2, LiNH2, LiF, and EuF3 as dopant in a radio frequency furnace. The crystal structure (space group Pa3̅ (no. 205), a = 10.72830(10) Å, R1 = 0.0401, wR2 = 0.0885, Z = 1) of the host compound Li24Sr12[Si24N47O]F was solved and refined on the basis of single-crystal X-ray diffraction data. Li24Sr12[Si24N47O]F is homeotypic with the nitridosilicate Li2SrSi2N4 as both compounds are characterized by the same tetrahedra network topology, but Li24Sr12[Si24N47O]F is an oxonitridosilicate and contains an additional F site. The implemented F is verified by EDX measurements as well as through calculations with PLATON. Besides, the electrostatic consistency of the refined crystal structure is proven by lattice energy calculations. The Eu2+-doped compound Li24Sr12[Si24N47O]­F:Eu2+ shows an orange to red luminescence (λmax = 598 nm; fwhm = 81 nm) under excitation with blue light, which differs from that of Li2SrSi2N4:Eu2+ (λem = 613 nm; fwhm = 86 nm) due to the additional F site. According to the blue-shifted emission, application in LEDs for sectors with low CRI is conceivable.