Distribution of Al atoms in the clathrate-I phase Ba₈Al_xSi_46−x at x = 6.9

Abstract

The clathrate-I phase Ba8AlxSi46-x has been structurally characterized at the composition x = 6.9 (space group Pm3[combining macron]n, no. 223, a = 10.4645(2) Å). A crystal structure model comprising the distribution of aluminium and silicon atoms in the clathrate framework was established: 5.7 Al atoms and 0.3 Si atoms occupy the crystallographic site 6c, while 1.2 Al atoms and 22.8 Si atoms occupy site 24k. The atomic distribution was established based on a combination of (27)Al and (29)Si NMR experiments, X-ray single-crystal diffraction and wavelength-dispersive X-ray spectroscopy.

Earth Abundant Element Type I Clathrate Phases

“…of Al at the 6 c site decreases. This is similar to what has been discovered in Ba 8 Al x Si 46-x samples by neutron diffraction study; when x increases from 6 to 15, to accommodate more Al atoms, more Al atoms go to 24 k site [6,34]. …”

The impact of boron atoms on clathrate-I silicides: composition range of the borosilicide K8−xBySi46−y

“…The framework topology matches the connectivity of group 14 atoms 4b(E14) 0 and group 13 Zintl-anions 4b(E13) − , which form a variety of ternary representatives. [1][2][3][4] In particular, ternary silicon and germanium clathrates with E13 = Al, [5][6][7][8][9][10][11] Ga, [12][13][14][15][16][17] In [18][19][20] have been studied thoroughly, often motivated by the search for new thermoelectric materials. 12,13 Clathrate compounds often exhibit a broad homogeneity range, and their compositions do not necessarily follow the Zintl rule.…”

Zintl Defects in Intermetallic Clathrates

“…Tools and techniques used for these analyses have to some extend been implemented, refined or developed in the Research Field Chemical Metals Science at the MPI CPfS. Examples are the program suite WINCSD, [18] elaborate metallography methods, [19] transmission electron microscopy with atomic resolution, [20,21] the development of new preparation methods [11,[22][23][24] as well as advanced theoretical approaches like the electron localizability indicator. [25,26] The present personal selection of significant contributions to research on intrinsic vacancy defects in clathrates aims at identifying significant input of Yuri Grin in the context of contemporaneous research rather than covering the highly-developed topic in full detail.…”