Synthesis and Structures of the Quaternary Chalcogenides of the Type KLnMQ4 (Ln = La, Nd, Gd, Y; M = Si, Ge; Q = S, Se)

✍ Scribed by Ping Wu; James A. Ibers

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 336 KB
• Volume: 107
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1357

✦ Synopsis

Some new quaternary compounds of the type (\mathrm{K} L n M \mathrm{Q}{4}(\operatorname{Ln}=\mathrm{La}, \mathrm{Nd}, \mathrm{Gd}, \mathrm{Y} ; M=\mathrm{Si}, \mathrm{Ge}); (Q=\mathrm{S}, \mathrm{Se})) have been synthesized by the reaction of (\mathrm{K}{2} \mathrm{~S}{5}) or (\mathrm{K}{2} \mathrm{Se}{5}) with lanthanide sulfides or selenides and elemental (\mathrm{Ge}) or (\mathrm{Si}) at (1000^{\circ} \mathrm{C}). The crystal structures of two of these compounds have been determined by (\mathrm{X})-ray diffraction techniques and are isostructural. Crystal data: (\mathrm{KLaGeS}{4})-space group (P 2_{\mathrm{I}}, M=378.84, Z=2, a=6.653(1), b=6.679(2), c=8.643(2) \AA \AA, \beta=107.57(1)^{\circ}(T=115 \mathrm{~K})), (V=366.1(1) \AA^{3}, D_{x}=3.436, \lambda\left(\mathrm{Mo} K \alpha_{1}\right)=0.7093 \AA, \mu=113.9 \mathrm{~cm}^{-1}, R_{\mathrm{w}}\left(F^{2}\right)=0.060) for 2613 observations and 66 variables, (R(F)=0.022) for 2534 observations having (F_{0}^{2}>2 \sigma\left(F_{0}^{2}\right)); (\mathrm{KLaGeSe}{4})-space group (P 2{\mathrm{I}}, M=566.44, Z=2, a=6.875(3), b=7.002(2), c=8.942(4) \AA, \beta=) (107.84(2)^{\circ}(T=115 \mathrm{~K}), V=409.8(3) \AA^{3}, D_{x}=4.590, \lambda\left(\mathrm{MoK} \alpha_{1}\right)=0.7093 \AA, \mu=267.8 \mathrm{~cm}^{-1}), (R_{w}\left(F^{2}\right)=0.100) for 3083 observations and 66 variables, (R(F)=0.041) for 2965 observations having (F_{0}^{2}>2 \sigma\left(F_{0}^{2}\right)). The other compounds synthesized appear to crystallize in the same structure type. The structure consists of two-dimensional ({ }{x}^{2}\left[\mathrm{LnMQ}{4}^{-}\right])layers separated by (\mathrm{K}^{+})cations in trigonal prismatic sites. The layers consist of (L n Q_{7}) distorted monocapped trigonal prisms and (M Q_{4}) tetrahedra that share edges and corners. The resultant structure is related to those of (\mathrm{Eu}{2} \mathrm{GeS}{4}) and (\mathrm{ScPS}{4}). The diffuse reflective UV-visible spectrum of (\mathrm{KLaGeS}{4}) has been measured. From measurements of magnetic susceptibility vs temperature both (\mathrm{KNdGeS}{4}) and (\mathrm{KGdGeS}{4}) show Curie-Weiss behavior. 11993 Academic Press, Inc.