Structural investigation and luminescence properties of the Ce-3(SiS4)(2)X(X= Cl, Br, I) family and the La3-xCex(SiS4)(2)I (0 <= x <= 1) solid solution

Recently prepared Ce-3(SiS4)(2)I exhibits a strong room temperature lumines cence in the blue region of the visible spectrum associated to a Ce-III-5d( 1) --> Ce-III-4f(1) electronic transition. In order to approach the emissio n mechanisms, the La3-xCex(SiS4)(2)I family has been investigated by optica l techniques at 6 and 300 K, At low temperature luminescence of the two cry stallographically distinct cerium cations was evidenced along with an intri nsic luminescence of the lanthanum matrix. The influence of the halogenide on the optical properties has been studied through the substitution of iodi ne by chlorine and bromine which permits us to follow the increase in energ y of the 4f-5d gap in the Cl<Br<I series. (C) 1999 Academic Press.