Reduced thermal degradation of the red-emitting Sr2Si5N8:Eu2+ phosphor via thermal treatment in nitrogen
The red phosphor of Sr2Si5N8:Eu2+ was synthesized by a solid state reaction. The as-synthesized phosphor powders were post-treated in a N2 atmosphere. The prepared samples were analyzed by XRD, FE-SEM, TG-DTA, FT-IR, zeta potential, cathodoluminescence (CL), photoluminescence (PL), quantum efficiencies (QEs), and temperature-dependent PL and QE techniques. After the thermal treatment in N2, it was found that the N2-treatment caused a negligible influence on the phase purity and particle morphology; the surface of the phosphor particle became more hydrophilic; the isoelectric point (IEP) of the suspension containing phosphor powder shifted to a higher pH value; the edge area (formed surface layer) of the phosphor particle had lower CL intensity than the inner part but it inhibited the surface damage caused by e-beam irradiation; more significantly, the formed surface layer plays a passivating role in preventing the Eu2+ activator from being oxidized, consequently, effectively reducing thermal degradation that deteriorates the PL intensity of the Sr2Si5N8:Eu2+ phosphor.