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Quaternary Ln−M−O−Q oxychalcogenides with structures containing 2D [Ln 2 O 2 ] 2+ layers including (a) ZrCuSiAs structure for LnMOQ phases, (b) Ln 2 O 2 M 2 OQ 2 phases, and (c) MQ 2 layers (from above) in cation-ordered ZrCuSiAs-related phases Ln 2 O 2 MQ 2 containing M 2+ ions, with Ln, M, O, and Q ions shown in blue, cyan, pink, and yellow, respectively.
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Mixed-anion systems have garnered much attention in the past decade with attractive properties for diverse applications such as energy conversion, electronics, and catalysis. The discovery of new materials through mixed-cation and single-anion systems proved highly successful in the previous century, but solid-state chemists are now embracing an ex...
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... 2+ sheets are separated by chalcogenide-rich layers (of net negative charge), and the layered structures of these materials ( Figure 5) can have a significant role in determining physical properties. 30 ZrCuSiAs structured materials are composed of alternating fluorite-like [Ln 2 O 2 ] 2+ layers and anti-fluorite-like [M 2 Q 2 ] 2− (M = transition metal) layers of edge-linked M + Q 4 tetrahedra (e.g., LnCuOQ (Ln = Bi, lanthanide). ...
Citations
... 38 It is becoming clear that the structures of rare-earth oxychalcogenides cannot be extrapolated in a simple way from chalcogenides and that more complex structurebuilding principles are at play in these mixed-anion systems. 44,45 In particular, there is a preference for the RE and O atoms to be bonded together in recurring structural motifs involving RE 4 O tetrahedra. Furthermore, in contrast to the observation that sulfides and selenides are often isostructural, the assumption does not necessarily extend to oxysulfides and oxyselenides; for example, notwithstanding their identical compositions, LaGaS 2 O and LaGaSe 2 O have different structures. ...
... These coordination geometries are similar to those found in Sm 3 GaSe 5 O. 38 The longer RE−Se distances The edge-sharing RE 4 O tetrahedra, which are fragments of the fluorite-type structure, are a recurring theme in rare-earth oxychalcogenides. 44,45 They are usually manifested as twodimensional slabs, as found in many layered oxychalcogenides (e.g., LaCuSO 20 and RE 4 Ga 2 S 5 O 4 29,34,35 ) but can be excised further into strips of varying widths, 64 as found here and other instances (e.g., Sm 3 GaSe 5 O 38 and La 4 Ga 2 Se 6 O 3 40 ). The strips of RE 4 O tetrahedra in RE 4 Ga 2 Se 7 O 2 are arranged in the same herringbone pattern as in an orthorhombic polymorph of LaInS 2 O, which also crystallizes in space group Pnma with an identical Wyckoff sequence (c 15 ), 33 but the connectivity of the group-13 and chalcogen atoms is quite different (Figure 3). ...
... When surveying the database, no RE 3 BO 6 or RE 3 BS 6 compounds can be found, suggesting that the title compounds cannot be obtained via straightforward O/S substitution. When compared with other RE-Q-B x O y or RE oxychalcogenide compounds [32,34,[43][44][45][46][47][48][49][50][51], apart from the B-O units, RE 3 S 3 BO 3 also show unique REO x Q y polyhedral units. In fact, all the three types of REO x Q y units REOS 6 , REO 4 S 3 , and REO 3 S 6 are present in other RE oxychalcogenides, however, RE 3 S 3 BO 3 is the only case that these three types of units coexist in one structure. ...
Exploration of new compounds belonging to unusual families is always attractive for the everlasting development of material science. Here, three isomorphic rare-earth sulfide borates RE 3 S 3 BO 3 (RE = Nd, Tb, Dy) have been obtained via a facile metal oxide-boron-sulfur solid-state routine. Their centrosymmetric triclinic structures feature 3D framework built by three types of REO x S y units, viz. REOS 6 , REO 4 S 3 , and REO 3 S 6. Their structural relationship with similar phases and lanthanide contraction rule are discussed. Their optical band gaps are measured to be 2.59-2.70 eV, and the corresponding theoretical calculations are also performed. This work enriches the rarely studied chalcogenide borate system and is conducive to discovering more inorganic materials.
... sites. Corey et al., 69 and more recently Wang et al. 24 72 It's striking that a strong electron-hole separation is indicated by the shape of the photocurrent response in both Sr 6 Cd 2 Sb 6 S 10 O 7 (figure 6) and LaGaS 2 O. 68 It has been proposed that polar aspects to the structure enhance electron-hole separation in oxysulfides 19 ...
The layered metal oxychalcogenide materials have gained significant attention in recent years due to the numerous applications in various emerging fields. Among them, the bismuth (Bi)-based ternary and quaternary oxychalcogenide...
Intergrowth compounds contain alternating layers of chemically distinct subunits that yield composition-tunable synergistic properties. Synthesizing nanoparticles of intergrowth structures requires atomic-level intermixing of the subunits rather than segregation into stable constituent phases. Here we introduce an anionic subunit insertion reaction for nanoparticles that installs metal chalcogenide layers between metal oxide sheets. Anionic [CuS]- subunits from solution replace interlayer chloride anions from LaOCl to form LaOCuS topochemically with retention of crystal structure and morphology. Sodium acetylacetonate helps extract Cl- concomitant with the insertion of S2- and Cu+ and is generalized to other oxychalcogenides. This topochemical reaction produces nanoparticles of ordered mixed-anion intergrowth compounds and expands nanoparticle ion exchange chemistry to anionic subunits.
Herein, the crystal structures and physical properties of two previously unreported barium seleno-germanates, Ba6Ge2Se12 and Ba7Ge2Se17, are presented. Ba6Ge2Se12 adopts the P21/c space group with a = 10.0903(2) Å, b = 9.3640(2) Å, c = 25.7643(5) Å, and β = 90.303(1)°, whereas Ba7Ge2Se17 crystallizes in the Pnma space group with a = 12.652(1) Å, b = 20.069(2) Å, c = 12.3067(9) Å. Both structures feature polyatomic anion disorder: [Se2]2- in the case of Ba6Ge2Se12 and [GeSe5]4- in the case of Ba7Ge2Se17. The anion disorder is verified by comparing pair distribution functions of ordered and disordered models of the structures. These anions are split unevenly across two possible sets of atomic coordinates. The optical band gaps obtained from the powdered samples are found to be 1.75 and 1.51 eV for Ba6Ge2Se12 and Ba7Ge2Se17, respectively. Differential scanning calorimetry experiments indicate that the compounds are stable under the exclusion of air up to at least 673 K. The thermal diffusivity measurements revealed thermal conductivities reaching values as low as 0.33 W m-1 K-1 in both compounds at 573 K.
We present a combined experimental and computational study on the recently reported oxysulfide Sr6Cd2Sb6S10O7. Our spectroscopy and photoelectrochemical measurements and tests for photocatalytic activity indicate the potential of Sr6Cd2Sb6S10O7 for photocatalytic applications. In particular, the transient photocurrent response shows a reproducible photogenerated current which depends on light intensity and which indicates an efficient electron-hole separation upon visible light illumination. Density functional theory calculations, combined with crystal orbital Hamiltonian population analysis, give insights into the electronic structure of Sr6Cd2Sb6S10O7 and the origin of its physical properties. Our comprehensive investigation into Sr6Cd2Sb6S10O7 reveals the roles of its polar structure, polar Sb3+ coordination environments, and the 5s2 lone pair in making this compound a potential candidate for solar water splitting photocatalysis.
