Investigating the Chemical Ordering in Quaternary Clathrate Ba8AlxGa16- xGe30
Artikel i vetenskaplig tidskrift, 2021

Recently, there has been an increased interest in quaternary clathrate systems as promising thermoelectric materials. Because of their increased complexity, however, the chemical ordering in the host framework of quaternary clathrates has not yet been comprehensively analyzed. Here, we have synthesized a prototypical quaternary type-I clathrate Ba8AlxGa16-xGe30 by Czochralski and flux methods, and we employed a combination of X-ray and neutron diffraction along with atomic scale simulations to investigate chemical ordering in this material. We show that the site occupancy factors of trivalent elements at the 6c site differ, depending on the synthesis method, which can be attributed to the level of equilibration. The flux-grown samples are consistent with the simulated high-temperature disordered configuration, while the degree of ordering for the Czochralski sample lies between the ground state and the high-temperature state. Moreover, we demonstrate that the atomic displacement parameters of the Ba atoms in the larger tetrakaidecahedral cages are related to chemical ordering. Specifically, Ba atoms are either displaced toward the periphery or localized at the cage centers. Consequently, this study reveals key relationships between the chemical ordering in the quaternary clathrates Ba8AlxGa16-xGe30 and the structural properties, thereby offering new perspectives on designing these materials and optimizing their thermoelectric properties.


Yifei Zhang

Chalmers, Kemi och kemiteknik, Tillämpad kemi

Joakim Brorsson

Chalmers, Kemi och kemiteknik, Tillämpad kemi

Takashi Kamiyama

High Energy Accelerator Research Organization

Takashi Saito

High Energy Accelerator Research Organization

The Graduate University for Advanced Studies (SOKENDAI)

Paul Erhart

Chalmers, Fysik, Kondenserad materie- och materialteori

Anders Palmqvist

Chalmers, Kemi och kemiteknik, Tillämpad kemi

Inorganic Chemistry

0020-1669 (ISSN) 1520-510X (eISSN)

Vol. 60 22 16977-16985

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