Synthesis and Structures of Ternary Chalcogenides of Aluminum and Gallium with Stacking Faults: KMQ2 (M=Al, Ga; Q=Se, Te)

✍ Scribed by Joonyeong Kim; Timothy Hughbanks

• Book ID: 102974889
• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 500 KB
• Volume: 149
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1999.8523

✦ Synopsis

The synthesis and crystal structures of new ternary chalcogenides of aluminum and gallium, KMQ 2 (M ‫؍‬ Al, Ga; Q ‫؍‬ Se, Te) are reported. These compounds were synthesized by solid-state reaction at 8003C in Nb containers. The single-crystal structures of KMTe 2 (M ‫؍‬ Al, Ga) have been determined; KAlTe 2 , a ‫؍‬ 11.808(2) A > , b ‫؍‬ 11.812(2) A > , c ‫؍‬ 16.456(3) A > , ‫؍‬ 100.32(3)3, C2/c (No. 15, Z ‫؍‬ 16); KGaTe 2 , a ‫؍‬ 11.768(3) A > , b ‫؍‬ 11.775(3) A > , c ‫؍‬ 16.503(4) A > , ‫؍‬ 100.36(2)3, C2/c (No. 15, Z ‫؍‬ 16). The fundamental building blocks of the title compounds are adamantane-like M 4 Q 10

layers by sharing terminal chalcogen atoms with adjacent supertetrahedra. These layers form a stack up to the c axis with each layer rotated by 903 relative to its neighbors. Potassium cations are located inside trigonal prisms formed by six chalcogen atoms. Stacking faults up the c* axis are evidenced by streaks in oscillation photographs. Only half of the data set is a4ected by this type of faulting. We demonstrate both analytically and by use of the DIFFaX program that our structural model for the faulting is consistent with the observed streaking patterns.