Charge compensation effects of alkali metal ions M+ (Li+, Na+, K+) on luminescence enhancement in red-emitting Ca3Si2O7:Eu3+ phosphors

Red-emitting Ca3Si2O7:Eu3+ and Ca3Si2O7:Eu3+, M+ (M = Li, Na, K) phosphors were prepared via a solid-state reaction. The effects of Eu3+ doping concentration and alkali metal ions M+ co-doping on the structure and luminescence performance of Ca3Si2O7:Eu3+ were investigated. X-ray diffraction patterns demonstrated that the Ca3Si2O7:Eu3+ phase synthesized at 1400 °C was consistent with the standard Ca3Si2O7 structure. Characteristic emission peaks of Ca3Si2O7:Eu3+ phosphors were revealed at 593 nm and 617 nm under excitation at 394 nm, which relate to the 4f electron transitions of Eu3+ ions. After co-doping M+ as a charge compensator, the luminescence intensity of red-emitting Ca3Si2O7:Eu3+, M+ phosphors were significantly improved by 2.62-, 1.80-, and 2.92-fold for Li+, Na+, K+ co-doping, as well as the luminescence lifetime compared with that of Eu3+-doped Ca3Si2O7. Moreover, actual LEDs with excellent chromaticity parameters were manufactured via coating the as-prepared phosphor onto a 395 nm n-UV chip. All results indicate that the Ca3Si2O7:Eu3+, M+ red-emitting phosphor has an excellent potential application as a red component in white light-emitting diodes.