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Structural, Spectroscopic, Magnetic and Thermal Properties in the [SrM(C 3 H 2 O 4 ) 2 (H 2 O) 5 ] · 2 H 2 O (M = Mn, Fe, Co, Ni) System: Precursors of SrMO 3– x Mixed Oxides
Author(s) -
Gil de Muro Izaskun,
Insausti Maite,
Lezama Luis,
Pizarro José L.,
Arriortua Maria I.,
Rojo Teófilo
Publication year - 1999
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(199906)1999:6<935::aid-ejic935>3.0.co;2-m
Subject(s) - chemistry , monoclinic crystal system , octahedron , antiferromagnetism , crystallography , crystal structure , cobalt , x ray crystallography , analytical chemistry (journal) , inorganic chemistry , diffraction , condensed matter physics , physics , chromatography , optics
The [SrM(C 3 H 2 O 4 ) 2 (H 2 O) 7 ] (M = Mn, Fe, Co, Ni) compounds have been prepared and characterised by chemical analysis and X‐ray diffraction. The crystal structure of [SrCo(C 3 H 2 O 4 ) 2 (H 2 O) 5 ] · 2 H 2 O has been solved [monoclinic, P 2 1 / c , Z = 4, a = 6.880(1), b = 14.360(2), c = 15.800(2) Å. β = 101.69(1)°]. The compound exhibits a three‐dimensional chain/snake structure consisting of –CoO 6 –[SrO 7 ] ∞ –CoO 6 – repeating units parallel to the [0 1 1] and [0 –1 1] directions. UV/Vis data are consistent with the cations being in a high‐spin octahedral symmetry. Magnetic measurements show antiferromagnetic interactions for all compounds with approximate θ values of –0.5 K, except for the cobalt compound (–24.5 K) where the decrease of the χ m T curve can also be attributed to the spin‐orbit coupling. Thermal analyses performed in air and under nitrogen show three consecutive steps: dehydration, ligand pyrolysis, and inorganic residue evolution. Thermal treatments in tubular furnaces were performed in order to obtain pure SrMO 3– x phases. In all cases the oxides are nonstoichiometric and oxygen‐deficient with structures related to that of perovskite. Lower temperatures and reaction times than those given in the literature have been used when using the ceramic method. These “soft” treatments gave rise to homogeneous particles of small grain size.