Garnet-based red emitting phosphors Li6MLa2Nb2O12: Eu3+ (M=Ca, Sr, Ba): Photoluminescence improvement by changing crystal lattice

A series of novel red emitting phosphors Li6M(La1−xEux)2Nb2O12 (M=Ca, Sr, Ba; 0≤x≤0.3) were synthesized by solid state reaction, and their structures and photoluminescence properties were investigated in detail. The excitation spectrum of Li6M(La1−xEux)2Nb2O12 revealed two mainly excitation bands at 393 nm and 464 nm, which match well with the two popular emissions from near-UV and blue LED chips. Upon the 464 nm light excitation, Li6MLa2Nb2O12:Eu3+ phosphors exhibit a red emission centered at 608 nm, originated from the 5D0–7F2 transition of Eu3+ ions. The Eu3+ surrounding crystal lattice environment in the garnet-based host was changed by altering the c sites element with different radii alkaline earth Ba, Sr, and Ca. The evident photoluminescence enhancement was observed in Li6M(La1−xEux)2Nb2O12 phosphors with the decreasing of the c sites ionic radius. The emission intensity of the optimized Li6Ca(La0.8Eu0.2)2Nb2O12 (λexc=464 nm) phosphor is about two times higher than that of Y2O3:Eu3+ (λexc=467 nm) under blue light excitation. In addition, the quenching mechanism and the relationship between the structure and photoluminescence property were also discussed.