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  • Author or Editor: B. Randhawa x
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Abstract  

Solid state photolysis of alkali tris(malonato)ferrates(III), i.e., M3[Fe(CH2C2O4)3]xH2O (M=Li, Na, K, NH4) has been studied employing Mössbauer, infrared and reflectance spectroscopic techniques. The complexes were irradiated for 300 hours using a medium pressure mercury vapour lamp of 250 W, Photodecomposition led to the formation of an iron(II) intermediate, M2[FeII(CH2C2O4)2(H2O)2] (M=Li, Na, K) which on prolonged standing in air oxidized to M[FeIII(CH2C2O4)2(H2O)2]. However, in case of ammonium complex, FeIICH2C2O4·2H2O once formed remained stable. The extent of photoreduction showed the sequence: NH4, K>Li>Na. The results have been compared with those of alkali tris (oxalato) ferrates(III).

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Abstract  

Thermolysis of cesium bis (citrato) ferrate (III) trihydrate, Cs3[Fe(C6H5O7)2].3H2O, has been studied in the temperature range of 373–1073 K in static air atmosphere, using Mössbauer and infrared spectroscopy and thermogravimetric methods. The anhydrous complex decomposed into an iron (II) intermediate at 453 K and -Fe2O3 of varying particle sizes in successive stages. Finally a solid state reaction between -Fe2O3 and cesium carbonate/oxide gives fine particles of cesium ferrite (CsFeO2) at a temperature lower than that of conventional ceramic method.

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Abstract  

The thermal decomposition of cesium tris(oxalato) ferrate(III) dihydrate, Cs3 Fe(ox)3 2H2O has been studied at various temperatures in air, employing Mössbauer and infrared spectroscopies, and thermogravimetric methods. The complex undergoes reduction to an iron(II) intermediate at 473 K. The particle size of -Fe2O3 formed during thermolysis increases with increasing decomposition temperature. Finally, a solid state reaction between -Fe2O3 and cesium carbonate/oxide occurs, leading to the formation of fine particles of cesium ferrite (CsFeO2).

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Abstract  

Thermal decomposition of managanese hexa(formato)ferrate(III)hexahydrate, i.e., Mn3[Fe(HCOO)6l2·6H2O has been studied upto 700°C in static air atmosphere employing TG, DSC, XRD, IR and Mössbauer spectroscopic techniques. The anhydrous complex decomposed directly into ferric oxide and manganese carbonate in successive stages without undergoing reduction to iron(II) intermediate. Finally a solid state reaction between Fe2O3 and manganese carbonate leads to the formatin of manganese ferrte (MnFe2O4) at a temperature (655°C) much lower than for ceramic method. A saturation magnetization value (4 Ms) of 2550 Gauss makes MnFe2O4 suitable for functioning at high frequencies.

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Abstract  

Thermal decomposition of alkali dihydroxo tetrapropionato ferrates(III), M3[Fe(C2H5COO)4(OH)2]xH2O (M=Li, Na, K) has been studied upto 973 K. The complexes were calcined isothermally at various temperatures i. e., 473, 573, 773 and 973 K. The intermediates/products have been characterized by Mössbauer, infrared spectroscopies and XRD powder diffraction. The anhydrous complexes directly decompose to give -Fe2O3 and alkali metal carbonate without undergoing reduction to iron(II) moiety. An increase in the particle size and internal magnetic field of -Fe2O3 has been observed with increasing decomposition temperature. At higher temperature (973 K) MFeO2 is formed as the final thermolysis product due to a solid state reaction between -Fe2O3 and alkali metal carbonate.

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Abstract  

Thermal decomposition of sodium tris(maleato)ferrate(III) hexahydrate, Na3[Fe(C4H2O4)3]·6H2O and sodium tris(fumarato)ferrate(III) heptahydrate, Na3[Fe(C4H2O4)3]·7H2O has been studied upto 973 K in static air atmosphere employing TG, DTG, DSC, XRD, Mössbauer and infrared spectroscopic techniques. Dehydration of the maleate complex is complete at 455 K and the anhydrous complex immediately undergoes decomposition till α-Fe2O3 and sodium carbonate are formed at 618 K. In the final stage of remixing of cations, a solid state reaction between α-Fe2O3 and sodium carbonate leads to the formation of α-NaFeO2 at a temperature (773 K) much lower than for ceramic method. Almost similar mode of decomposition has been observed for the fumarate complex. A comparison of the thermal stability shows that the fumarate precursor decomposes at a higher temperature than the maleate complex due to the trans geometry of the former.

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Abstract  

Mössbauer spectra of alkali tris(maleato) ferrates(III), i.e., M3[Fe(C2H2C2O4)3nH2O [M=Li, Na, K, Cs] at 300 K display a doublet. The Mössbauer parameters indicate these complexes to be high spin with octahedral symmetry. The isomer shift shows a decreasing trend with the increase in electronegativity/polarizing power of the substituent cation (Li+, Na+, K+, Cs+). A linear correlation between isomer shift values and the (Fe−O) stretching frequencies has also been observed.

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Abstract  

Thermal decomposition of ammonium tris (malonato) ferrate (III) tetrahydrate, i. e. (NH4)3[Fe(CH2C2O4)3]·4H2O has been studied up to 973 K in static air atmosphere employing Mössbauer and infrared spectroscopies, and non-isothermal techniques (TG, DTG, DTA). The anhydrous complex decomposes into an iron (II) intermediate at 453 K. The iron (II) species on further heating is reoxidized to -Fe2O3 as the final thermolysis product. An increase in particle size of -Fe2O3 with increasing decomposition temperature has been observed. The results are compared with the analogous oxalate complex.

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Abstract  

Thermal analysis of zinc hexa(formato)ferrate(III) decahydrate, Zn3 [Fe(HCOO)6]2 10H2O has been investigated up to 800°C in static air atmosphere employing TG, DSC, XRD, IR, ESR and Mössbauer spectroscopic techniques. After dehydration at 160°C, the anhydrous complex decomposes into α-Fe2 O3 and zinc carbonate in successive stages. Subsequently the cations remix to yield fine particles of zinc ferrite, ZnFe2 O4 , as a result of solid state reaction between α-Fe2 O3 and zinc carbonate at a temperature (600°C) much lower than for ceramic method.

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Abstract  

The thermal decomposition of alkali tris(maleato)ferrates(III), M3 [Fe(C2 H2 C2 O4 )3 ] (M =Li, Na, K) has been studied isothermally and non-isothermally employing simultaneous TG-DTG-DTA, XRD, Mssbauer and IR spectroscopic techniques. The anhydrous complexes decompose in the temperature range 215–300C to yield Fe(II)maleate as an intermediate followed by demixing of the cations forming α-Fe2 O3 and alkali metal maleate/oxalate in successive stages. In the final stage of remixing of the cations (430–550C) a solid state reaction occurs between α-Fe2 O3 and alkali metal carbonate leading to the formation of fine particles of respective ferrites. The thermal stabilities of the complexes have been compared with that of alkali tris(oxalato)ferrates(III).

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