Tunable photoluminescence in Ba1-xSrxSi3O4N2: Eu2+/ Ce3+, Li+ solid solution phosphors induced by linear structural evolution

A series of oxynitride phosphors, Ba1-xSrxSi3O4N2: Eu2+/ Ce3+, Li+ (0 ≤ x ≤ 0.5) have been synthesized through a solid state reaction method at a high temperature. The influence of Sr2+-doping on the structure and photoluminescence properties of Ba1-xSrxSi3O4N2: Eu2+/ Ce3+, Li+ was studied systemically. All of the samples were found to retain their hexagonal crystal structures with the linear lattice shrinking upon the increase of Sr2+ concentration, indicating that Ba2+ is substituted by Sr2+ to form the intermediate solid-solution compositions of Ba1-xSrxSi3O4N2. It is noteworthy that red shifts of about 30 and 7 nm in the emission spectra of Eu2+ and Ce3+-activated samples were observed, respectively, through the Sr substitution at Ba sites from 0 to 0.5, originating from the increment of crystal field strength and Stokes shift. The thermal quenching stability, fluorescence decay behavior and CIE values were discussed and compared. Based on these results, the Ba1-xSrxSi3O4N2: Eu2+ phosphors are considered to be potential candidate phosphors applicable to n-UV LED for solid-state lighting.