ISSN:
0044-2313
Keywords:
Ternary halides
;
synthesis
;
crystal structures
;
ionic conductivity
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
Ternary Halides of the A3MX6 Type. III [1, 2]. Synthesis, Structures, and Ionic Conductivity of the Halides Na3MX6 (X = Cl, Br)The bromides Na3MBr6 crystallize with the stuffed LiSbF6-type structure (type I; M = Sm—Gd) or with the structure of the mineral cryolite (type II; M = Gd—Lu). The structure types were refined from single crystal X-ray data (Na3SmBr6: trigonal, space group R3, a = 740.8(2) pm, c = 1 998.9(8) pm, Z = 3; Na3YBr6: monoclinic, space group P21/n, a = 721.3(4) pm, b = 769.9(2) pm, c = 1 074.8(4) pm, β = 90.60(4)°, Z = 2). Reversible phase transitions from one structure to the other occur. The phase transition temperatures were determined for the bromides as well as for the chlorides Na3MCl6 (M = Eu—Lu). The refinement of both structures for one compound was possible for Na3GdBr6 (I: trigonal, space group R3, a = 737.1(5) pm, c = 1 887(2) pm, Z = 3; II: monoclinic, space group P21/n, a = 725.2(1) pm, b = 774.1(3) pm, c = 1 080.1(3) pm, β = 90.76(3)°, Z = 2). All compounds exhibit ionic conductivity of the sodium ions which decreases with the change from type I to type II. The conductivity of the bromides is always higher when compared with the respective chlorides.
Notes:
Die Bromide Na3MBr6 kristallisieren im aufgefüllten LiSbF6-Typ (Typ I; M = Sm—Gd) oder im Kryolith-Typ (Typ II; M = Gd—Lu). Die Strukturen wurden anhand von Einkristalldaten verfeinert (Na3SmBr6: trigonal, Raumgruppe R3, a = 740,8(2) pm, c = 1 998,9(8) pm, Z = 3; Na3YBr6: monoklin, Raumgruppe P21/n, a = 721,3(4) pm, b = 769,9(2) pm, c = 1 074,8(4) pm, β = 90,60(4)°, Z = 2). Beide Strukturen sind reversibel ineinander umwandelbar. Die Umwandlungstemperaturen der Bromide wurden ebenso wie die der Chloride Na3MCl6 (M = Eu—Lu) bestimmt. An Na3GdBr6 wurden beide Strukturen an Einkristallen bestimmt (I: trigonal, Raumgruppe R3, a = 737,1(5) pm, c = 1 887(2) pm, Z = 3; II: monoklin, Raumgruppe P21/n, a = 725,2(1) pm, b = 774,1(3) pm, c = 1 080,1(3) pm, β = 90,76(3)°, Z = 2). Alle Verbindungen zeigen Natrium-Ionenleitfähigkeit, die beim Übergang vom Typ I in den Typ II stark abnimmt. Die Bromide zeigen, verglichen mit den Chloriden, jeweils eine bessere Leitfähigkeit.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/zaac.19956210321
