Crystal structure and optical properties of (Ba,Eu)2SiS4

Structural and optical properties of europium-doped barium thiosilicate are reported. The whole range of the Eu concentration x in Ba 2(1− x ) Eu 2 x SiS 4 is studied. The lattice constants continuously decrease with the increase in x in the orthorhombic (0 ⩽ x ⩽ 0.6) or in the monoclinic (0.7 ⩽ x ⩽ 1) structures. This decrease changes the strength of the crystal field for Eu 2+ and thus shifts the wavelength of photoluminescence (PL) (490–570 nm). For Eu-doped Ba 2 SiS 4 ( x = 0.01 and 0.02), the PL efficiency is 40%, and the decay time of its single exponential profile is obtained to be 240 ns. The decrease in the PL efficiency and the change in the decay profile (0.05 ⩽ x ⩽ 0.9) are explained by the enhancement of the cross relaxation among Eu 2+ ions.