Microwave-hydrothermally synthesized (Sr1-x-yCexTby)Si2O2-δN2+μ phosphors: efficient energy transfer, structural refinement and photoluminescence properties

A facile microwave-assisted hydrothermal method was developed to prepare oxynitride-based (Sr1-x-yCexTby)Si2O2-delta N2+mu phosphors. The microwave-assisted hydrothermal process led to lower synthesis temperatures and shortened heating duration. The obtained powders exhibited a narrow size distribution. The Rietveld refinement reveals the obtained phosphors to have a triclinic crystal system. For Ce3+ doped SrSi2O2N2 phosphors, the emission spectrum exhibited an asymmetric band at 447 nm (lex 322 nm), corresponding to the blue hue. As Ce3+ and Tb3+ ions were co-doped into SrSi2O2N2, the energy transfer occurred via a dipole-dipole interaction. With increasing the Tb3+ concentration, the Tb3+ emission intensity enhanced and reached a maximum with the Tb3+ concentration of 2 mol%, then decreased due to the concentration quenching effect. It is also observed that the intensity of the Ce3+ emission peak decreased gradually. This indicates the effective energy transfer from Ce3+ to Tb3+ ions. The CIE coordinate of (Sr1-x-yCexTby)Si2O2-delta N2+mu phosphors shifted from the blue region towards the green region with increasing Tb3+ concentration. The above findings indicate that the emitting colors of the microwave-hydrothermally derived (Sr1-x-yCexTby)Si2O2-delta N2+mu phosphors can be tuned over a wide range under UV excitation.