Structural, spectroscopic, magnetic and thermal properties in the [SrM(C3H2O4)2(H2O)(5)]center dot 2 H2O (M = Mn, Fe, Co, Ni) system: Precursors of SrMO3-x mixed oxides
Ig. De Muro et al., Structural, spectroscopic, magnetic and thermal properties in the [SrM(C3H2O4)2(H2O)(5)]center dot 2 H2O (M = Mn, Fe, Co, Ni) system: Precursors of SrMO3-x mixed oxides, EUR J INORG, (6), 1999, pp. 935-943
The [SrM(C3H2O4)(2)(H2O)(7)] (M=Mn, Fe, Co, Ni) compounds have been prepare
d and characterised by chemical analysis and X-ray diffraction. The crystal
structure of [SrCo(C3H2O4)(2)(H2O)(5)]. 2 H2O has been solved [monoclinic,
P2(1)/c, Z = 4, a = 6.880(1), b = 14.360(2), c = 15.800(2) Angstrom. beta
= 101.69(1)degrees]. The compound exhibits a three-dimensional chain/snake
structure consisting of -CoO6-[SrO7](proportional to)-CoO6- repeating units
parallel to the [0 1 1] and [0 -1 1] directions. UV/Vis data are consisten
t with the cations being in high-spin octahedral symmetry. Magnetic measure
ments show antiferromagnetic interactions for all compounds with approximat
e 0 values of -0.5 K, except for the cobalt compound (-24.5 K) where the de
crease of the chi(m) T curve can also be attributed to the spin-orbit coupl
ing. Thermal analyses performed in air and under nitrogen show three consec
utive steps: dehydration, ligand pyrolysis, and inorganic residue evolution
. Thermal treatments in tubular furnaces were performed in order to obtain
pure SrMO3-x phases. In all cases the oxides are nonstoichiometric and oxyg
en-deficient with structures related to that of perovskite. Lower temperatu
res and reaction times than those given in the literature have been used wh
en using the ceramic method. These "soft" treatments gave rise to homogeneo
us particles of small grain size.