Structure of the lanthanum chlorosilicate La3(SiO4)Cl5

Abstract

Introduction. Investigation of the LaC13-La203-SiO2 system shows the existence of three ternary phases: La3(SiO4)2CI, La(SiO3)C1 and La3(SiO4)CIs. These halosilicates are favourable host lattices for high luminescence efficiency of rare-earth ions under UV excitation. The structure of La3(SiO4)2C1 has been recently determined (Gravereau, Es-Sakhi & Fouassier, 1988). The present paper reports an X-ray study of a single crystal of La3(SiO4)CIs.

Inorganic Lanthanide Compounds with Complex Anions

“…Halide ortho -silicates of the rare-earth elements are mainly known with Cl - as the halide component. Those with the composition M 3 Cl(SiO 4 ) 2 crystallize either in a monoclinic (A-type) or an orthorhombic (B-type) modification. − The A-type occurs with the larger M 3+ ions and the B-type with the smaller ones (cf. Table ).…”

“…Table ) due to a slightly different orientation of the SiO 4 4- tetrahedra (Figure ). With La 3 Cl 5 (SiO 4 ) and Ce 3 Cl 5 (SiO 4 ), two examples of chlorine-rich chloride ortho -silicates are known. , They are isotypic and show a certain similarity to the trichlorides LaCl 3 and CeCl 3 (UCl 3 type of structure) when four Cl - ions of the tripled formula are substituted for SiO 4 4- . For the discrete silicate anions a statistical distribution on two cyrstallographic positions is found.…”

Hydrogenoxosilicates of the lanthanides

“…Due to the very short distance between the central positions of the face-shared tetrahedra (d(Si 4+ · · ·Si 4+ ) = 59 pm) and the half occupation of the silicon position (8d, sof(Si) = 0.516 (14)), it is obvious that only one of the two partial tetrahedra can be fully occupied with silicon while the other one is not. A similar dilemma has been encountered with the chloride oxosilicates M 3 Cl 5 [SiO 4 ] (Pnma or C2/m; M = La-Nd, Tb) [12][13][14] already. In two of the monoclinic subgroups of Pnma, P2 1 /n11 and P112 1 /a namely, a satisfactory ordered occupation pattern of Si 4+ within the trigonal bipyramids occurs, in which the "upper" partial tetrahedra are filled in a regarded strand and the "lower" tetrahedra in the adjacent strands, so that real discrete [SiO 3 (OH)] 3− anions emerge.…”

Samarium chloride sulfide thiosilicate, Sm3ClS2[SiS4]

“…Up to now, the following homologue groups have been published: the lanthanide iodide thiosilicates Ln 3 I[SiS 4 ] 2 (Ln = La±Nd, Sm and Tb) (Gauthier et al, 1998a,b;Hatscher & Urland, 2001, 2002c, the lanthanide bromide thiosilicates Ln 3 Br[SiS 4 ] 2 (Ln = La±Nd, Sm and Gd) (Hatscher & Urland 2002a), and the lanthanide chloride thiosilicates Ln 3 Cl[SiS 4 ] 2 (Ln = La±Pr) (Hatscher & Urland, 2002b), all crystallizing in the monoclinic space group C2/c. These compounds are isotypic with the so called A-type of the lanthanide chloride oxosilicates, ®rst discovered by Gravereau et al (1988). With Nd 3 ClS 2 [SiS 4 ] (Hatscher & Urland, 2002d), a new compound in this system was published with no oxo analogue so far known.…”