The site occupancy and optical investigations on a novel Li2CaSi2N4: Eu2+ orange-red phosphor

Eu2+ activated lithium-containing nitridosilicates attract great attention in the field of phosphors research due to their outstanding luminescent performance. Herein, a nitridolithosilicate Li2CaSi2N4:Eu2+ orange-red phosphor was successfully synthesized by solid-state reaction. Upon the 400 nm excitation, the phosphor exhibits a slightly wide and asymmetric emission profile. Meanwhile, the emission band broadens with the increase of Eu2+ ions concentration. It may result from Eu2+ occupying different positions of Ca2+ in the host, which can give rise to different degrees of nephelauxetic effect and crystal field splitting. Considering the effect of the centroid shift (εc) and crystal field splitting (εcfs), the sources of two luminescence centers are confirmed by calculating the total shift (D(A)) of the 4f5d level of Eu2+ in a host. In addition, the temperature dependence luminescent properties of Li2CaSi2N4:Eu2+ are investigated as well and the thermal-sensitizing mechanism is discussed.