Synthesis and Structures of New Layered Ternary Manganese Tellurides:  AMnTe₂ (A = Li, Na)

Abstract

The layered structures of many transition metal chalcogenides are of interest because they are known to easily accommodate various metal ions or molecules in their van der Waals gaps. 1 Most early investigations of the first-row ternary transition metal chalcogenides concentrated on sulfides and selenides, which display a rich structural variety. [2][3][4][5][6] Only three types of ternary manganese telluride compounds, A 2 MnTe 2 (A ) K, Rb, Cs), A 6 -MnTe 4 (A ) Na, K), and A 2 Mn 3 Te 4 (A ) Rb, Cs), have been reported. 3,7,8 The first has a one-dimensional structure with edgesharing tetrahedra, the second possesses isolated [MnTe 4 ] 6tetrahedra, and the third compound has a layered structure. We have synthesized new layered compounds, LiMnTe 2 and NaMnTe 2 , by direct solid state and cation exchange reactions. These new compounds have unusual polar layers.

Synthesis and Structures of New Layered Ternary Manganese Selenides: AMnSe2 (A=Li, Na, K, Rb, Cs) and Na2Mn2Se3

“…Our research on these systems originated with the discovery of the layered compounds, AMnTe (A"Li, Na) (8,9). These compounds exhibit polar [MnTe Te]\ layers, in which MnTe tetrahedra share three corners.…”

“…No systematic absences were observed. NaMnSe is isostructural with NaMnTe so the atomic positions of NaMnTe were used to begin re"nement (9). Isotropic re-"nement showed reasonable thermal coe$cients for all atoms, and subsequent anisotropic re"nement gave 4.74 and 9.37% for "nal R(F) and wR (F) with I'2 (I).…”

The new sodium tellurido manganates(II) Na2Mn2Te3, Na2Mn3Te4, Na2 AMnTe3 (A=K, Rb), and NaCsMnTe2

“…arrangement of tellurium ions [24]. The pure Li and Na manganates(III) AMnSe 2 [17] and AMnTe 2 [25] as well as the mixed-valent phase Na 3 Mn 4 Te 6 (25% Mn III , [24]) likewise contain h.c.p. chalcogen arrangements with layer-wise Mn-filled tetrahedral voids.…”

“…(iii) The structures of the layered ('phyllo') lithium and sodium chalcogenido metallates are fundamentally different from those of the larger alkali cations. Li/Na: The layered manganates(II) with the smaller lithium or/and sodium cations can be derived from the trigonal layers of tetrahedra in the CaAl 2 Si 2 -type structure: whereas the mixed-valent manganat(II/III) NaMn 1.56 Te 2 show a statistical occupation of the tetrahedral voids in the aristotype, the manganates(III) (Li/Na)MnSe 2 [17] and (Li/Na)MnTe 2 [25] exhibit polar layers, in which only ½ of the tetrahedra of each layer are occupied, crystallographically leading to the t2 subgroup P3m1 (Fig. 5, left).…”

Inorganic structures in space group P3m1; coordinate analysis and systematic prediction of new ferroelectrics

“…LiMnTe 2 [unlisted, ICSD release 2007-1]. Mo K, single-crystal diffractometry, -scan absorption corrections, 164 independent I(hkl) > 4I(hkl), R = 0.0501, wR 2 = 0.0918 at 293 K, U ij , Flack parameter not reported (Kim et al, 1998). The atomic coordinates are closely comparable to those in x2.4.1 with Á max ' 0.57 Å and u 33 ' 0.15 Å , see Table S2(b).…”