New luminescent rare earth activated oxynitridosilicates and oxynitridogermanates with the apatite structure

New luminescent oxynitrides based on the apatite structure doped with Eu 2+ and Ce 3+ have been prepared by ammonolysis of oxysilicate or oxygermanate precursors. The host compounds have the general formula La 10-xSr x(Si/Ge) 6O 27-x/2-3y/2N y. When doped with divalent europium or trivalent cerium they present blue, green, yellowish green or orange luminescence under UV/blue excitation. Remarkable long wavelength emissions centred beyond 500 nm are observed for the Ce 3+ activated oxynitridosilicates and oxynitridogermanates, with compositions La 8.9Ce 0.1SrSi 6N 0.37O 25.95, La 8.9Ce 0.1SrSi 6N 1.06O 24.91 (λ em = 545 nm) and La 9.9Ce 0.1Ge 6N 2.46O 23.31 (λ em = 590 nm). The treatment of precursor oxides with the required cationic ratios in NH 3 gas was used as a convenient general method to prepare the oxynitride materials at moderate temperatures. This allowed decreasing the nitriding temperature from 1600-1400 °C to 1050-600 °C with respect to the method generally used for the synthesis of luminescent (oxy)nitride silicates, the solid state reaction between oxides, nitrides and carbonates under a N 2 or N 2-H 2 flow. © The Royal Society of Chemistry 2012.