ChemInform Abstract: On the Extended Series of Quaternary Zintl Phases Ca₁₃REMnSb₁₁ (RE: La—Nd, Sm, Gd—Dy).

Abstract

Single crystalline Ca14‐xLnxMnSb11 (Ln: La—Nd, Sm, Gd—Dy; x ≈ 1) is prepared from the elements in a molten Pb flux with a 20% Ln and a 50—70% Mn excess (Al2O3 crucible in evacuated silica tubes, 1000 °C, 24 h).

From the Ternary Phase Ca14Zn1+δSb11 (δ ≈ 0.4) to the Quaternary Solid Solutions Ca14–xRExZnSb11 (RE = La–Nd, Sm, Gd, x ≈ 0.9). A Tale of Electron Doping via Rare-Earth Metal Substitutions and the Concomitant Structural Transformations

“…As can be seen in Table 1, compositional variations within the series are remarkably small with the difference of RE content of ±0.06 from averaged value, which is on par and even less than the sample-to-sample variations from previous studies. 17,18 Rare-earth metal content from structural refinements of several single crystals from the same reaction batch, as well as from products made by different methods, is uniform and shows no statistically significant deviations from the presented values in Table 1. From earlier related work on Ca 14−x RE x MnSb 11 and Ca 14−x RE x MnBi 11 , the Sm-containing materials appeared to be somewhat of an outlier with samarium amounts varying more than 20%.…”

“…The same observation was made for the previously studied Ca 14−x RE x MnSb 11 and Ca 14−x RE x MnBi 11 (RE = La−Nd, Sm, Gd−Ho) series. 17,18 Large crystals of all Ca 13 REZnSb 11 compounds were obtained from Sn-flux, whereas Pb-flux afforded the desired phases in smaller crystal size. The exception to this observation was the parent Ca 14 ZnSb 11 phase, which for reasons that are not yet understood crystallized better in Pb-flux (vide supra).…”

“…These crystallographic parameters should typically be standardized, but considerable amount of previously published data exist in nonstandard settings. [10][11][12][13][14][15][16][17][18]26 Details of the data collection for Ca 14 ZnSb 11 and for the six members of the Ca 13 REZnSb 11 (RE = La−Nd, Sm, Gd) family are summarized in Table 1. Table 2 lists the fractional atomic coordinates and displacement parameters for Ca 14 ZnSb 11 and one RE-substituted variant Ca 13 LaZnSb 11 , chosen as a representative example; the crystallographic parameters for the five remaining structures are given in Tables S1−S5 (provided as Supporting Information).…”

“…The trends are similar to the patterns reported for the isostructural manganese analogs, suggesting that the geometric reasons put forth in the earlier studies can be used to rationalize the data presented in this work too. 17,18 Briefly, for all six refined structures, the rare-earth metals accumulate mostly at the Ca1 and Ca2 positions, accounting for more than 80% of the total rare-earth metal uptake. The relative occupancy of the Ca1 site significantly increases with an increase of an atomic number of rare-earth metals, whereas an inverse relationship is observed for the Ca2 site.…”

“…16 Analogous substitution studies on Mn-bearing "14−1−11" phases have recently been performed in our laboratory. 17,18 Starting with the parent Ca 14 MnSb 11 and Ca 14 MnBi 11 compounds, which do not represent electron-balanced compositions, our prior works have shown that the replacement of one Ca atom by one rare-earth metal atom (RE = rare-earth metal) restores the precise valence electron count; i.e., the resultant quaternary phases Ca 14−x RE x MnSb 11 and Ca 14−x RE x MnBi 11 (RE = La−Nd, Sm, Gd−Ho, x ≈ 1) behave as intrinsic semiconductors and should be considered as true Zintl phases. These studies were extended toward the Ca−Zn−Sb system, where a multitude of interesting ternary compounds are known and structurally characterized; however, a phase Ca 14 ZnSb 11 , which would be isolectronic and isostructural with Ca 14 MnSb 11 , is not known.…”