Synthesis Of Iron Sulfides: A Mössbauer Study

Facile synthesis and selected characteristics of two-dimensional material composed of iron sulfide and magnesium-based hydroxide layers (tochilinite)

“…The previous synthetic studies [37][38][39][40][41][42][43][44][45][46] have been largely aimed at mimicking the mineral formation processes, including extra-terrestrial ones, and commonly used strict precautions against oxidation of the iron sulfide part of tochilinite, akin to mackinawite [57][58][59][60], to preserve low-spin Fe 2+ . The materials manufactured here through the simple method contain high-spin ferric and ferrous cations, which are paramagnetic both at 293 and 4.2 K. At the same time, the low-temperature Mössbauer spectra show several magnetic ordered states attributed to the abovementioned iron centers in the sulfide layers, and Fe 3+ coordinated to OHand minor O 2ligands in Mg-based hydroxide sheets.…”

“…3, Table 2). It is likely that, akin to valleriite [50], doublets with the chemical shift δ = 0.3-0.4 mm/s and quadrupole splitting ∆ of 0.4-0.6 mm/s are due to Fe 3+ -S centers, and the ones with δ ≥ 0.4 mm/s and ∆ of 1±0.2 mm/s originate from high-spin Fe 3+ cations in octahedral OHenvironment (Fe 3+ -6OH), whereas the quantities of Fe 2+ -OH centers (δ ∼ 1 mm/s, ∆ > 2 mm/s [40][41][42][56][57][58][59][60]) are minor. The electron densities and electric field gradients at Fe 2+ nuclei in tetrahedral coordination to S are close to those for Fe 3+ -6OH centers so their signals are difficult to resolve.…”

“…Parameters of fitting the Mössbauer spectra of tochilinites synthesized* (a) without doping and (b) doped with Al or (c) Li, measured at 298 K and 4.2 K. δ is a chemical shift relative to α-Fe (mm/s), ∆ is a quadrupole splitting (mm/s), W -a width of a doublet line or internal 34 and external 16 lines for sextets (mm/s), H -internal magnetic field (kOe), A -a fraction of a particular iron position (%). The spectra reported in the literature for tochilinites [35,[40][41][42] and mackinawite FeS [56][57][58][59][60] composed of similar tetrahedral sulfidic sheets connected with van-der-Waals forces typically show a narrow maximum from low-spin Fe 2+ -S centers with δ ~ 0.4 mm/s at room temperature and about 0.47 mm/s at cryogenic temperatures, along with contributions of other Fe species formed as reaction by-products [40][41][42] or arose upon oxidation of the ferrous sulfide [57][58][59][60]. The hyperfine magnetic structure emerges in mackinawite since its aging causes deficit of Fe and S-S bonding, and also formation of high-spin Fe 3+ and Fe 2+ instead of singlet Fe 2+ .…”

“…Valleriite (CuFeS 2 )⋅(Mg,Al,Fe)(OH) 2 [19][20][21][22][23][24][25][26][27] and tochilinite mFeS⋅n(Mg,Fe)(OH) 2 [30][31][32][33][34][35][36] are the most known and important of them; particularly, valleriite ores of Noril'sk ore provenance (Russia) are of commercial importance but not involved in the exploitation because of the lack of processing technologies. Synthetic valleriite and tochilinite have been prepared and characterized too [37][38][39][40][41][42][43][44][45][46][47][48][49][50]; however, the yields of the target substances were lower than 50%, and those were substantially contaminated by the reaction by-products. Another group of layered iron chalcogenide-hydroxide materials with the composition Fe(Se,S)⋅(Li,Fe)OH and some their derivatives [51][52][53][54][55] synthesized in the recent years are attracting much attention because of the superconducting properties but little efforts have been made to study other characteristics and applications.…”

Facile synthesis and selected characteristics of two-dimensional material composed of iron sulfide and magnesium-based hydroxide layers (tochilinite)

“…Valleriite (CuFeS2)(Mg,Al,Fe)(OH)2 [19][20][21][22][23][24][25][26][27] and tochilinite mFeSn(Mg,Fe)(OH)2 [30][31][32][33][34][35][36] are the most known and important of them; particularly, valleriite ores of Noril'sk ore provenance (Russia) are of commercial importance but not involved in the exploitation because of the lack of processing technologies. Synthetic valleriite and tochilinite have been prepared and characterized too [37][38][39][40][41][42][43][44][45][46][47][48][49][50]; however, the yields of the target substances were lower than 50%, and those were substantially contaminated by the reaction by-products. Another group of layered iron chalcogenide-hydroxide materials with the composition Fe(Se,S)(Li,Fe)OH and some their derivatives [51][52][53][54][55] synthesized in the recent years are attracting much attention because of the superconducting properties but little efforts have been made to study other characteristics and applications.…”