Flux-adjusted phase transformation from Ca_2SiO_4 to Ca_3Si_2O_7 with Eu^(2+) activator for white light emitting diodes

摘要

Eu2+ -activated reddish-orange-emitting Ca3Si2O7 phosphors were synthesized with the addition of NH4Cl flux.When the phosphors were synthesized in a nominal composition of (Ca0.99Eu0.01)3Si2O7 without flux addition,a Ca3Si2O7 phase responsible for reddish-orange emission was identified to coexist with an intermediate phase of a-Ca2SiO4 for green emission.With the addition of NH4Cl flux,a-Ca2SiO4 was suppressed while the pure phase Ca3Si2O7 was obtained as the flux content was 3 wt%.Through varying the amount of flux,the emission color of samples can be tuned from green to reddish-orange,corresponding to the phase transformation from a-Ca2SiO4 to Ca3Si2O7.Through optimizing the doping concentration of Eu2+ ,the optimized photoluminescence (PL) properties for reddish-orange emission can be achieved,which makes this kind of phosphor prospective in the applications of the phosphor-converted white light emitting diodes (PC-WLEDs).