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The authors analyse the possibility of obtaining manganese-zinc ferrite through the transformations of polynuclear coordination compounds (pcc), either in the solid state or in a reaction medium. Polynuclear coordination compound precursors with the general molecular formula: [Fe(II)xFe(III)y(Mn0.5Zn0.5)(C2O4)2(OH)y+2(H2O)2] with 0.2<x<1.0, 1.0<y<1.8 and x+y=2, obtained through a forced hydrolysis were characterized by chemical and physicochemical procedures. A non-isothermal kinetic analysis of the thermal decomposition steps showed that all of them are described by contracting geometry rate equation. The influence of the thermal treatment on the properties of the final products of transformation was evidenced.

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Thermal analysis of some polynuclear coordination compounds

Ligand tartarate, precursors of LnFeO3 perovskites

Journal of Thermal Analysis and Calorimetry
Authors: L. Patron, P. Budrugeac, A. Balu, Oana Carp, L. Diamandescu and M. Feder

Abstract  

The thermal behaviour of five polynuclear coordination compounds containing tartaric anion as ligand, namely (NH4)3[LnFe(C4O6H4)3(OH)3] (Ln=La and Eu), (NH4)2[PrFe(C4O6H4)3(OH)2] and (NH4)[LnFe(C4O6H4)3(OH)]3H2O (Ln=Nd and Gd) was investigated. The reaction progress was studied by TG/DTA and FTIR measurements. Oxalates and oxocarbonates were identified as intermediates. In the case of Ln=La, Nd, Pr, Eu and Gd, pure LnFeO3 was obtained as final decomposition product. The thermal decomposition of Eu-Fe compound, leads to a mixture of mixed (ortho-ferrite (EuFeO3) and garnet (Eu3Fe5O12)) and simple oxides (Eu2O3 and α-Fe2O3).

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Abstract  

A TG, DTG and DTA study of three polynuclear coordination compounds, containing Al(III)-Mg(II), namely (NH4)4[Al2Mg(C4O5H4)4(OH)4]⋅2H2O, (NH4)4[MgAl2(C4H4O6)4(OH)4]⋅3H2O and (NH4)2[Al2Mg(C6O7H11)5(OH)5]⋅3H2O, has been reported together with the associated thermal decomposition mechanism rationalized in terms of intermediate products. As decomposition end-product, magnesium-aluminum spinel is obtained. The values of MgAl2O4 mean crystallite size depend on the anionic ligand contained by the precursor compound, varying in the order: malate (143 Å) ligand contained by the precursor compound, varying in the order: malate (143 Å)

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Abstract  

This paper reports an investigation of the thermal stabilities of the class of coordination compounds containing lanthanide ions Ln(III) (Ln=La, Sm, Eu, Dy, Er), Co(II) ions and oxalate anions C2O 4 2– . The thermal decomposition steps were identified, and in some cases the values of the non-isothermal kinetic parameters were determined.

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Results are presented on the thermal behaviour of [Fe(III)2Cu(C2C4)2(OH)4(H2O)2] precursor of copper ferrite. An investigation of the decomposition steps and intermediates was followed by a non-isothermal kinetic analysis of the processable steps.

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Abstract  

The thermal behaviour of four coordination compounds (NH4)6[Y3Fe5(C4O5H4)6(C4O5H3)6]·12H2O, (NH4)6[Y3Fe5(C6O7H10)6(C6O7H9)6]·8H2O, (NH4)6[Er3Fe5(C4O5H4)6(C4O5H3)6]·10H2O and (NH4)6[Er3Fe5(C4O6H4)6(C4O6H3)6]·22H2O has been studied to evaluate their suitability for garnet synthesis. The thermal decomposition and the phase composition of the resulted decomposition compounds are influenced by the nature of metallic cations (yttrium-iron or erbium-iron) and ligand anions (malate or gluconate).

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-milling [ 9 ] or solid state reaction [ 6 ] and non-conventional ones like sol–gel [ 10 ], co-precipitation, auto-combustion [ 11 , 12 ] and thermal decomposition of polynuclear coordination compounds [ 13 ]. In this paper, we present a study on

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Abstract  

Nickel–zinc ferrites have been synthesized via thermal decomposition of polynuclear coordination compounds containing as ligand the anion of malic acid, namely (NH4)[Fe2NixZn1–x(C4H4O5)(OH)3]nH2O (x =0.25, 0.5 and 0.75, n=3 and 5). A comparison between the thermal behaviour of the studied polynuclear coordination compounds is inferred. Fe2NixZn1–xO4 (n=0.25, 0.5 and 0.75) ferrites with mean particle sizes of 65–85 and free from other phases are formed after a heating treatment of only one hour at 500C.

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