Synthesis of Rare-Earth Polychalcogenides by Moderate Temperature Solid-State Metathesis

✍ Scribed by John H. Chen; Peter K. Dorhout

• Book ID: 102603707
• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 243 KB
• Volume: 117
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1995.1279

✦ Synopsis

Alkali metal polychalcogenide salts of the form (A_{2} Q_{x}) (where (A=\mathrm{Na}, \mathrm{K} ; Q=\mathrm{S}, \mathrm{Se}, \mathrm{Te} ; \boldsymbol{x}=1,2,3,4) ) have been used in moderate temperature solid-state metathesis reactions with lanthanoid halides, (\operatorname{Ln} X_{3}(L n=L a, P r ; X=C l, B r)), to prepare four phases of lanthanoid chalcogenides at temperatures below (400^{\circ} \mathrm{C}). For lanthanum, (\alpha-\mathrm{LaS}{2}, \boldsymbol{\beta}-\mathrm{LaS}{2}, \mathrm{LaSe}{2}), and (\mathrm{LaTe}{3}) were prepared and an irreversible phase transformation at (450^{\circ} \mathrm{C}) between the metastable (\alpha) - and thermodynamically stable (\beta-\operatorname{LaS}{2}) was observed. For praseodymium, (\alpha-\operatorname{PrS} \mathrm{S}{2}, \mathrm{PrSe}{2}), and (\mathrm{PrTe}{3}) were prepared and no phase transition from (\alpha) - to (\boldsymbol{\beta})-PrS (\mathrm{P}_{2}) was observed. O 1995 Academic Press. Inc.