Structure, Thermodynamic, and Magnetic Properties of Ln4PdO7 with Ln=La, Nd, Sm, Eu, and Gd

✍ Scribed by M Andersson; J Grins; M Nygren

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 271 KB
• Volume: 146
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1999.8387

✦ Synopsis

The structure of Nd 4 PdO 7 has been determined and re5ned using the Rietveld method and combined CuK 1 X-ray and neutron powder data in space group P1 with unit cell a ‫؍‬ 15.972(2), b ‫؍‬ 7.1927( 7), c ‫؍‬ 6.9160(6) A > , ‫؍‬ 96.299(4), ‫؍‬ 131.643(3), ‫؍‬ 121.438(3)3, V ‫؍‬ 353.83(6) A > 3 and Z ‫؍‬ 2, to R F ‫؍‬ 2.0% (neutron data) and R F ‫؍‬ 6.2% (X-ray data). The structure is closely related to the monoclinic La 4 PdO 7 structure and exhibits Nd atoms coordinated by seven O atoms and Pd atoms coordinated by a square of O atoms. Isolated chains of trans-corner-sharing PdO 4 squares are straight in the La 4 PdO 7 structure and staggered in the Nd 4 PdO 7 structure. Electron and X-ray powder di4raction data show that Ln 4 PdO 7 with Ln ‫؍‬ Sm, Eu, and Gd is isostructural with Nd 4 PdO 7 . The enthalpies of dissolution of Ln 4 PdO 7 (Ln ‫؍‬ La, Nd) in 1.000 M HCl have been measured with an in-house built calorimeter, and from these values the enthalpies of formation for the compounds have been calculated. The decomposition temperatures of Ln 4 PdO 7 with Ln ‫؍‬ La and Nd in oxygen have been determined by thermogravimetric measurements and found to decrease from 1645؎10 K for La 4 PdO 7 to 1540؎10 K for Nd 4 PdO 7 . Using these data, an Ellingham diagram has been constructed assuming temperature-independent H3 f and S3 f . The magnetic susceptibilities of Ln 4 PdO 7 with Ln ‫؍‬ La, Nd, Sm, Eu, Gd, recorded in the temperature range 10+320 K, were found to be in agreement with the expected ones for noninteracting Ln 3؉ ions. 1999 Academic Press