Type-I silicon clathrates containing lithium

Abstract

The intermetallic phase [LixBa8-x][LiySi46-y] is the first example of a clathrate-I silicide containing lithium with the peculiarity that the Li atoms occupy both cage and framework positions. The phase was obtained by ambient-pressure solid-state reactions at 400 degrees C between Ba4Li2Si6 and the binary clathrate phase Ba8-xSi46 applying different experimental approaches. In this reaction, Li atoms substitute Si atoms of the framework at site 6c (space group Pm (3) over barn) and fill up the Ba-deficient dodecahedral Si-20 cages at site 2a. The presence of Li atoms in the clathrate phase was proven by combined X-ray powder diffraction, Li-7 and Si-29 solid-state NMR analyses. Incorporation of lithium markedly increased the lattice parameter of the clathrate phase, e. g. from a = 10.3200(2)

Zintl Defects in Intermetallic Clathrates

“…Although the chemistry of intermetallic clathrates has been continuously developed for approximately 70 years, further fundamental discoveries are on the horizon. The preparation of vacancy clathrate-I compounds by low-temperature redox reactions [22][23][24] is expected to open a route to unique metastable clathrate-I phases. In addition, other advanced preparation techniques are still expanding the number of accessible binary clathrate phases.…”

“…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.…”

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

“…Plasma treatment under controlled H 2 flow was realized in a microwave furnace (MLS) for 20 minutes (P = 1200 W, p(H 2 ) ≈ 29 Si NMR signals (static echo measurements) show a small Knight shift typical for widely electronically balanced silicon clathrate-I compounds. [28][29][30] 2 mbar) at temperatures below 300°C. The purified boron powder was free of oxygen and hydrogen according to chemical analysis and still amorphous.…”

“…27,31 This indicates bad-metal behavior of the clathrate phase for all samples, which is in agreement with electronically widely (but not exactly) balanced chemical compositions. [28][29][30]…”

Reactivity and Controlled Redox Reactions of Salt‐like Intermetallic Compounds in Imidazolium‐Based Ionic Liquids

“…The development of derivative heterogeneous gas‐solid reactions succeeded in the preparation of a number of metastable intermetallic clathrates [10–13] . Here, the key redox processes such as the reaction of the precursors with hydrogen chloride or alkyl chlorides are equivalent to the above‐discussed ones for precursors in direct contact with quaternary ammonium ions in the ILs.…”