Origin of PL intensity increase of CaMgSi2O6:Eu2+ phosphor after baking process for PDPs application

We have synthesized blue-emitting CaMgSi2O6:Eu2+ (CMS) and evaluated its thermal stability after baking process. To evaluate its thermal stability, CMS was baked in air at 500 and 600 °C for 20 min, respectively, and compared with BaMgAl10O17:Eu2+ (BAM) treated in the same condition. After baking process, CMS showed somewhat increased photoluminescence (PL) intensity with baking temperature. To investigate the reasons behind the increase of PL intensity after baking process, vacuum ultraviolet (VUV)/PL, electron spin resonance (ESR), X-ray photoelectron spectroscopy (XPS) techniques were applied. From the ESR and the XPS analyses, it is noted that spectral intensity of Eu2+ ion somewhat increased. It was believed that due to charge balance Eu3+ ions reduced to Eu2+ ions during the baking process in air. It is clear that the concentration of Eu2+ increased after the baking process in air and it leads to slight increase of the VUV/PL intensity of CMS phosphor.