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Single Crystals of C–La 2 Se 3 , C–Pr 2 Se 3 , and C–Gd 2 Se 3 with Cation‐Deficient Th 3 P 4 ‐Type Structure
Author(s) -
Folchnandt Matthias,
Schleid Thomas
Publication year - 2001
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/1521-3749(200107)627:7<1411::aid-zaac1411>3.0.co;2-x
Subject(s) - dodecahedron , crystallography , metal , trigonal crystal system , chemistry , crystal structure , rare earth , molar ratio , caesium , mineralogy , inorganic chemistry , biochemistry , organic chemistry , catalysis
Ruby‐red, bead‐shaped single crystals of C‐type La 2 Se 3 (a = 905.21(6) pm), Pr 2 Se 3 (a = 891.17(6) pm), and Gd 2 Se 3 (a = 872.56(5) pm) are obtained by oxidation of the respective rare‐earth metal (M = La, Pr and Gd) with selenium (molar ratio 2 : 3) in evacuated silica tubes at 750 °C in the presence of fluxing CsCl within seven days. Their crystal structure belongs to a cation‐deficient Th 3 P 4 ‐type variant (cubic, I 4 3d) according to M 2.667 □ 0.333 Se 4 (Z = 4) or M 2 Se 3 (Z = 5.333) offering coordination numbers of eight (Se 2– arranged as trigonal dodecahedra) to the M 3+ cations. In spite of the high Cs + activity in molten CsCl, no cesium incorporation into the M 5.333 □ 0.667 Se 8 ‐frame structure (e. g. as CsM 5 Se 8 with Z = 2) could be achieved, judged from both results of electron beam X‐ray microanalyses and refined occupation factors of the metal position very close to x = 8/9 for M 3x Se 4 .