Structure, thermodynamic, and magnetic properties of Ln{sub 4}PdO{sub 7} with Ln = La, Nd, Sm, Eu, and Gd
- Stockholm Univ. (Sweden)
The structure of Nd{sub 4}PdO{sub 7} has been determined and refined using the Rietveld method and combined CuK{alpha}{sub 1} X-ray and neutron powder data in space group P{bar 1} with unit cell a = 15.972(2), b = 7.1927(7), c = 6.9160(6) {angstrom}, {alpha} = 96.299(4), {beta} = 131.643(3), {gamma} = 121.438(3){degree}, V = 353.83(6) {angstrom}{sup 3} and Z = 2, to R{sub F} = 2.0% (neutron data) and R{sub F} = 6.2% (X-ray data). The structure is closely related to the monoclinic La{sub 4}PdO{sub 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{sub 4} squares are straight in the La{sub 4}PdO{sub 7} structure and staggered in the Nd{sub 4}PdO{sub 7} structure. Electron and X-ray powder diffraction data show that Ln{sub 4}PdO{sub 7} with Ln = Sm, Eu, and Gd is isostructural with Nd{sub 4}PdO{sub 7}. The enthalpies of dissolution of Ln{sub 4}PdO{sub 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{sub 4}PdO{sub 7} with Ln = La and Nd in oxygen have been determined by thermogravimetric measurements and found to decrease from 1645 {+-} 10 K for La{sub 4}PdO{sub 7} to 1540 {+-} 10 K for Nd{sub 4}PdO{sub 7}. Using these data, an Ellingham diagram has been constructed assuming temperature-independent {Delta}H{sub f}{degree} and {Delta}S{sub f}{degree}. The magnetic susceptibilities of Ln{sub 4}PdO{sub 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{sup 3+} ions.
- OSTI ID:
- 696676
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 2 Vol. 146; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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