A white powder of oxonitridosilicate Ca3Si2O4N2 was synthesized at 1450 °C from CaCO3, Si3N4 and SiO2. The crystal structure was refined using X-ray and neutron powder diffraction data with subsequent Rietveld refinements (Rwp = 7.35 for XRD and Rwp = 5.53 for NPD). The phase has a cubic unit cell with space group Pa (no. 205), cell parameters a = 15.0739(2) Å and Z = 24. In contrast with most layered oxonitridosilicates, such as MSi2O2N2 (M = Ca, Sr, Ba), Ba3Si6O9N4 and Ce4Si4O5N6, Ca3Si2O4N2 is constructed of highly corrugated 12-membered rings of [Si12O24N12], which is composed of [SiO2N2] tetrahedra. N atoms fully occupy the bridging sites and O atoms fully occupy the terminal sites. This structure is also supported by the 29Si NMR measurement. The photoluminescence of Ce3+ doped Ca3Si2O4N2 shows that the phosphor has a typical shouldered emission band peaking at 470 nm and the phosphor can be efficiently excited in the range 300–400 nm, which makes it an attractive candidate phosphor for the application in phosphor-converted light-emitting diodes (pc-LEDs).
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