Four ternary silicides in the La–Ni–Si system: from polyanionic layers to frameworks

Abstract

Four ternary La–Ni–Si compounds have been synthesized and characterized. They present ordered structures with extended 2D or 3D Ni/Si motifs.

Lan(n+1)+xNin(n+5)+ySi(n+1)(n+2)–z: A Symmetric Mirror Homologous Series in the La–Ni–Si System

“…The most prominent examples are the La (n+1)(n+2) Ni n(n−1)+2 Si n(n+1) series with four representatives (n = 2−5) 21 and the extended NaZn 13 -related 22 solid solution with multiple structural and compositional variations of La(Ni,Si) 12−13 . 23−25 Our recent exploration of the phase space yielded four new compounds�LaNi 2 Si, La 3 Ni 3 Si 2 , La 6 Ni 7 Si 4 , and La 2 Ni 3 Si 2 , 26 where the first one does not have an analogous known compound within the family of silicides, while the last one crystallized in its own structure type. La 3 Ni 3 Si 2 and La 6 Ni 7 Si 4 also show significant structural relationships with identical stacking motifs.…”

“…Our recent exploration of the phase space yielded four new compoundsLaNi 2 Si, La 3 Ni 3 Si 2 , La 6 Ni 7 Si 4 , and La 2 Ni 3 Si 2 , where the first one does not have an analogous known compound within the family of silicides, while the last one crystallized in its own structure type. La 3 Ni 3 Si 2 and La 6 Ni 7 Si 4 also show significant structural relationships with identical stacking motifs . Such a high density of compositions just in a narrow region (25–35 at.…”

The Ce–Ni–Si System Revisited: More Homologue Compounds?

“…While Ce 3 Ni 3 Si 2 has not been detected in the Ce–Ni–Si system, such a compound was detected recently in the La–Ni–Si system. 36 Indeed, La 3 Ni 3 Si 2 (Ce 3 Rh 3 Si 2 -type) shows a close resemblance with Ce 3 Ni 4 Si 2 and Ce 6 Ni 7 Si 4 . Due to infinite removal of the Ni chains, the only nickel fragment left in La 3 Ni 3 Si 2 is the Ni–Ni dumbbell.…”

“…While Ce 3 Ni 3 Si 2 has not been detected in the Ce–Ni–Si system, such a compound was detected recently in the La–Ni–Si system . Indeed, La 3 Ni 3 Si 2 (Ce 3 Rh 3 Si 2 -type) shows a close resemblance with Ce 3 Ni 4 Si 2 and Ce 6 Ni 7 Si 4 .…”

“…38 Thus, one must explore the lower-temperature region to inspect the formation of those phases. For example, La 3 Ni 4 Si 2 was reported to be stable below 750 °C 36 while single crystals of Ce 3 Ni 4 Si 2 and RE 6 Ni 7 Si 4 were obtained at 800 °C or higher. 11 Preference of formation with specific RE atoms can be seen from the fact that there are no reported isotypic RE 3 Ni 4 Si 2 compounds with RE atoms other than La and Ce.…”