Synthesis and Magnetic and Transport Properties of Sr₆V₉S₂₂O₂:  “AM₂S₅” Phases Revisited

Abstract

The compound Sr6V9S22O2 was prepared from SrS, sulfur, vanadium metal, and V2O5 at 950 degrees C in an evacuated quartz tube. The compound is rhombohedral, R3, with a = 8.7538(6) A, c = 34.934(3) A, and Z = 3, and shows strong preferred orientation in its XRD profiles (00l) due to the layered nature of the structure. The compound contains charged CdI2 type VS2 layers of formula [V7S14]4- separated by [Sr6(VOS3)2(S2)]4+ layers. The latter has VOS3(3-) tetrahedra and S2(2-) disulfide units linked by Sr2+ ions. Magnetic susceptibility and four-probe resistivity studies show essentially temperature-independent paramagnetism above 80 K and small gap semiconductor behavior, respectively. The compound has a positive Hall coefficient at room temperature. The relationship among Sr6V9S22O2, "SrV2S5" (J. Solid State Chem. 1996, 126, 189), and other AM2S5 phases is discussed.

Anion Ordering in Bichalcogenides

“…However, the sites have different multiplicities, according to the Wyckoff definition (4f and 2b), and probably should be divided as V 4+ (4f) and V 3+ (2b). In contrast, it can be expected from the stoichiometry that V is +4 in Ba3V2S4O3 [9,10] -octahedra were reported in Sr6V9S22O2 but no magnetic moment was observed, agreeing with a lack of true charge ordering [17]. However, in Ba15V12S34O3 three oxidation states (V 3+ , V 4+ , V 5+ ) were proven experimentally and a suggested charge ordering was presented (Figure 2), as based on the existence of a short vandyl bond, (V=O) 2+ , the HSAB principle, and Coulombic repulsion forces [18].…”

Ba3V2S4O3: A Mott Insulating Frustrated Quasi‐One‐Dimensional S=1 Magnet

“…[10][11][12] Furthermore, transition-metal sulfide oxides are of interest due to their possible applications [13,14] and ability to form anionic superlattices that result in unusual properties. [15,16] These superlattices invoke structurald imensionalities, such as layers in La 2 Co 2 Se 2 O 3 . [17] Charge disproportionation according to the hard-soft acid-base (HSAB) rule is probable in superlattices with lower(higher) cationic charges closet os ofter(harder) anions.…”

A new lanthanum titanium oxysulfide, La16Ti5S17+xO17, withx = 0.75 (9)

“…Not all combinations of atoms S2, S6 and S7 give a pair with a reasonable SÐS bond distance, and the most probable pairing is between two S2 atoms ($2.10 A Ê ). Similar (S 2 ) 2À dianions were also encountered in Sr 6 V 9 S 22 O 2 (Litteer et al, 2000). Another difference between the Nd and La analogues concerns the splitting of the Ti2-atom position.…”