Structure and Thermal Stability of the New Intermetallics MgPd2, MgPd3, and Mg3Pd5 and the Kinetics of the Iodine-Catalyzed Formation of MgPd2

✍ Scribed by Ch. Wannek; B. Harbrecht

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 442 KB
• Volume: 159
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2001.9138

✦ Synopsis

Three new binary intermetallics in the palladium-rich part of the magnesium+palladium system have been identi5ed and characterized by combining preparative methodologies with powder X-ray di4raction techniques and thermochemical analyses. MgPd 2 decomposing in the solid state at 628(2)3C adopts a Co 2 Si-type structure: space group Pnma, a ‫؍‬ 5.4421( 2), b ‫؍‬ 4.1673(2), c ‫؍‬ 8.0129(3) A s . MgPd 3 crystallizes in a Al 3 Zrtype structure: space group I4/mmm, a ‫؍‬ 3.92263(7), c ‫؍‬ 15.6527(4) A s . It decomposes in a peritectoid reaction at 704(2)3C. The kinetics of the iodine-catalyzed synthesis of MgPd 2 have been studied. The reactions seem to follow Ostwald:s step rule. Four intermediate phases were identi5ed, among them was Mg 3 Pd 5 , a previously unknown phase with a Ge 3 Rh 5 -type structure: space group Pbam, a ‫؍‬ 5.427(2), b ‫؍‬ 10.588(5), c ‫؍‬ 4.1304(12) A s .