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

Abstract

A facile microwave-assisted hydrothermal method was developed to prepare oxynitride-based (Sr_1−x−yCe_xTb_y)Si₂O_2−δN_2+μ 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 (λ_ex = 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 (Sr_1−x−yCe_xTb_y)Si₂O_2−δN_2+μ 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 (Sr_1−x−yCe_xTb_y)Si₂O_2−δN_2+μ phosphors can be tuned over a wide range under UV excitation.