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Gtlich, Bill, Trautwein: Mssbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009
FeII-III hydroxysalts green rusts, which are layered double hydroxides (LDH), are constituted of [FeII(1-x) FeIIIx (OH)2 ]x+ layers and [(x/n)An- (mx/n)H2O]x- interlayers that can incorporate various anions such as Cl-, CO32-, SO42-, HCOO-, C2O42-, SeO42- For Chloride GR1(Cl-):[FeII2FeIII(OH)6]+[Cl-2H2O]- Sulphate GR2(SO42-): [FeII4FeIII2(OH)12]2+[SO42-8H2O]2- Carbonate GR1(CO32-):[FeII4FeIII2(OH)12]2+[CO32-3H2O]2-There exist two types of space groups as determined by XRD: GR1 [R(-3)m] and GR2 [P(-3)m1] that depend on the shape of the anion. Mssbauer spectra display 2 ferrous doublets D1 & D2 (large D) and1 ferric doublet D3 (small D).
For GR1(CO32-): a = 0.317588(2) nm and c = 2.27123(3) nm
The in situ oxidation of green rusts by deprotonationUse a strong oxidant such as H2O2, Dry the green rust and oxide in the air, Violent air oxidation, Oxide in a basic medium
FeII6(1-x) FeIII6x O12 H2(7-3x) CO3FeII-III oxyhydroxycarbonate0 < x < 1Gtlich, Bill, Trautwein: Mssbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009
Evolution of Mssbauer spectra with measurement temperature displaying the ferrimagnetic behaviour of stoichiometric GR(CO32-) between 1.4 and 12 K.FeII4 FeIII2 (OH)12 CO3 ferrimagnetism
H = 130 kOeD = -3 mm s-1(a)1.4 KMssbauer spectra of GR(CO32-) sample oxidised violently by H2O2 and named ferric [GR(CO32-)*]1. Measurement temperatures are (a) 16 K, (c) 50 K, (d) 60 K and (e) 78 K. (b) and (f) are the hyperfine field distribution of (a) and quadrupole splitting distribution of (e) using a Voigt profile analysis, respectively.FeIII6 O12 H8 CO3 ferromagnetismGtlich, Bill, Trautwein: Mssbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009
Projections perpendicular to the c axis of a Fe layer with octahedrons of OH- ions that can be deprotonated or protonated for values of x = 0, 0.33, 0.67 and 1. There exist four ordered types of domain to match any intermediate composition as determined by x.
Hexagonal pavements of FeII and FeIII cations in the layers of (a) Fe(OH)2, (b) stoichiometric GR(CO32-) at x = 1/3, (c) GR(CO32-)* with 1/3 < x < 2/3, (d) GR(CO32-)* at x = 2/3, (e) GR(CO32-)* with 2/3 < x < 1 and (f) fully ferric GR(CO32-)* at x = 1. Long range order is displayed showing magnetic domains.