Chemical Pressure Control for Photoluminescence of MSiAl2O3N2:Ce3+/Eu2+ (M = Sr, Ba) Oxynitride Phosphors

Novel promising blue MSiAl2O3N2:Ce3+ (M = Sr, Ba) and green BaSiAl2O3N2:Eu2+ oxynitride phosphors with broad band emission for white light-emitting diodes are obtained in this study. The detailed energy transfer mechanism from Ce3+ to Eu2+ in SrSiAl2O3N2 is reported. Moreover, the unexpected red shift emission when the compositional variable x is increased from 0 to 0.92 in the Sr0.92-xBaxSiAl2O3N2:Ce-0.04(3+),Eu-0.04(2+) system is well investigated. The decrease in emission energy and the increase in thermal quenching barrier height of x are caused by a dominant chemical pressure compression effect on the activator sites, through which the replacement of Sr2+ (occupied by activators) by larger Ba2+ enhances the covalency of Sr-N/O bonding in spite of unit cell enlargement. The chemical pressure compression effect control for photoluminescence is verified by the ionic-radii equilibrium between 9-coordinate Sr-IX(2+) and (Ca-IX(2+), Ba-IX(2+)).