Acta Crystallographica Section B

Structural Science

Volume 55, Part 3 (June 1999)

Acta Cryst. (1999). B55, 341-347    [doi:10.1107/S0108768198018345]

Disparate atomic displacements in skutterudite-type LaFe₃CoSb₁₂, a model for thermoelectric behavior

B. C. Chakoumakos, B. C. Sales, D. Mandrus and V. Keppens

Abstract: Mean-square atomic displacements in lanthanum triiron cobalt dodecaantimonide, determined as a function of temperature using single-crystal neutron diffraction, show that the La atom exhibits an anomalously large displacement at room temperature, U_eq = 0.0196  (9)  Å², because it is too small to fill the atomic cage formed by the corner-linked octahedral framework of M₄Sb₁₂, M = Fe, Co. Site-occupancy refinements show 25% vacancies on the La site and an actual Fe:Co ratio of 2.17:1. Analysis of the temperature dependence of the atomic displacements identifies a significant temperature-independent component for the La atom ascribed to static disorder, which amounts to 19% of the room-temperature value. The large-amplitude rattling of the La atom can be effectively linked to the dramatic decrease of the lattice contribution to the thermal conductivity, which is a key factor for improving the thermoelectric behavior of these materials. This structure-property relationship offers a new paradigm for the exploration of thermoelectric materials.

Online 1 June 1999

	Structure factor file (SHELXL table format) (185.8 kbytes) Supplementary material
	Structure factor file (SHELXL table format) (206.4 kbytes) Supplementary material
	Structure factor file (SHELXL table format) (207.0 kbytes) Supplementary material
	Structure factor file (SHELXL table format) (65.2 kbytes) Supplementary material
	Structure factor file (SHELXL table format) (185.2 kbytes) Supplementary material
	Structure factor file (SHELXL table format) (183.8 kbytes) Supplementary material
	Structure factor file (SHELXL table format) (183.8 kbytes) Supplementary material
	Structure factor file (SHELXL table format) (183.8 kbytes) Supplementary material
	Structure factor file (SHELXL table format) (207.0 kbytes) Supplementary material

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