Synthesis and luminescence properties of green phosphors Ca6Sr4(Si2O7)3Cl2:Eu2+ for white light emitting diodes

Divalent europium-activated chlorosilicate Ca6Sr4(Si2O7)3Cl2:Eu2+ phosphors were synthesized by a conventional solid-state reaction under reductive atmosphere. These phosphors can be efficiently excited by UV–visible light from 320 to 420 nm, which matches that of a near UV-emitting InGaN chip. Under the 360 nm excitation, Ca6Sr3.97(Si2O7)3Cl2:0.03Eu2+ phosphor shows a strong and broad emission centering at 515 nm, which is attributed to the 5d→4f transition of Eu2+ ion. The mechanism of concentration quenching was determined to be the dipole–dipole interaction and the critical energy-transfer distance of Eu2+ was calculated as 3.31 nm. The CIE chromaticity coordinates of Ca6Sr3.96(Si2O7)3Cl2:0.03Eu2+ phosphor are (0.127, 0.770) according to the emission spectrum. It can be expected that Ca6Sr4(Si2O7)3Cl2:Eu2+ phosphor is a promising candidate as the green component for near-ultraviolet InGaN-based white LED.