Pure-red phosphor Ca3Si2O7:Eu2+ obtained by the CO reduction strategy

The discovery of pure-red emitting phosphor is great meaningful for the achievement of high color rendering index white light emitting diodes, but still a challenge due to the strict crystal field limitations. In this work, we demonstrate the preparation of a 630 nm pure-red emitting Ca3Si2O7:Eu2+ phosphor for the first time through a CO reduction strategy. The changes in crystal field strength caused by different methods for the preparation of Ca3Si2O7:Eu2+ are investigated and discussed based on the understanding of the thermodynamic theory and structure resolution. Finally, a white light-emitting diode with a high color rendering index (Ra = 98) is accomplished by combining the as-prepared Ca3Si2O7:Eu2+ pure-red emitting phosphor with a 375 nm chip and the commercial used blue and green phosphors. The results also demonstrate the generalizability of the weak reduction strategy for the exploration of "redder" Eu2+ doped phosphors.