Authors:B. Randhawa, P. Bassi, Sukhraj Randhawa, and Sandeep Kaur
Solid state photolysis of alkaline earth tris/malonato/ferrates/III/, i.e., M3[Fe(CH2C2O4)3]2.xH2O /M=Mg, Ca, Sr, Ba/ has been investigated employing Mössbauer, infrared and reflectance spectroscopic techniques. The complexes were irradiated for 400 h using a medium pressure mercury vapour lamp of 250 Watts. Photoreduction led to the formation of M[FeII(CH2C2O4)2(H2O)2]. The extent of photoreduction showed the following order: Ca>Sr>Mg>Ba. The results have been compared with those of analogous alkaline earth tris/oxalato/ferrates/III/.
Thermal decomposition of some hydroxy iron(III) carboxylates, i.e., iron(III) lactate, Fe(CH3CHOHCOO)3, iron(III) tartrate, Fe2(C4H4O6)3 and iron(III) citrate, Fe(C6H5O7) · 5H2O has been studied in static air atmosphere in the temperature range 298–773 K employing Mössbauer, infrared spectroscopies and themogravimetric methods. The compounds directly decompose to -Fe2O3 without undergoing reduction to iron(II) intermediates. An increase in particle size of -Fe2O3 has been observed with increasing decomposition temperature. The thermal stability follows the sequence: iron(III) tartrate > iron(III)citrate > iron(III)lactate.
Authors:B. Randhawa, K. Prabhjinder, and Sweety Kamaljeet
Thermal decomposition of cobalt hexa(formato)ferrate(III) decahydrate, Co3[Fe(HCOO)6]2. 10H2O, has been studied up to 973 K in static air atmosphere, employing TG, DTG, DSC, XRD, ESR, Mössbauer and infrared spectroscopic techniques. Dehydration occurs in two stages in the temperature range of 340–430 K. Immediately after the removal of the last water molecule the anhydrous complex undergoes decomposition till -Fe2O3 and cobalt carbonate are formed at 588 K. In the final stage of remixing of cations, a solid state reaction between -Fe2O3 and cobalt carbonate leads to the formation of CoFe2O4 at a temperature (953 K) much lower than for the ceramic method. A saturation magnetization value of 2310 Gauss of ferrite (CoFe2O4) shows its potential to function at high frequencies.
Mössbauer spectra of a series of the complexes of the type Na3[Fe/RCOO/6]xH2O /R=H, CH3, C2H5, C6H5/ has been recorded at 298±2 K. All display a quadrupole doublet with isomer shift and quadrupole splitting values in agreement with high spin iron/III/ octahedral geometry. The quadrupole splitting show an increasing trend with increasing polarizability of the substituent anion /RCOO–/. A linear correlation between quadrupole splitting values and the /Fe–O/ stretching frequencies has also been observed.
Thermal decomposition of some alkali tris (malonato) ferrate (III) tetrahydrates, i. e. M3 [Fe(CH2C2O4)3]·4H2O (M=Na, K) has been studied in the temperature range of 433–973 K in static air atmosphere using Mössbauer, IR and TG-DTG-DTA techniques. Mössbauer spectra are reported at different stages to study the mechanism of decomposition. The anhydrous complex decomposed into -Fe2O3 of varying particle sizes and alkali metal malonate/carbonate in successive stages. In the final stage of remixing of cations, a solid state reaction between -Fe2O3 and alkali metal carbonate/oxide gives fine particles of the respective ferrites at temperatures lower than for oxalate precursor or even for ceramic method. Thermal stability obeys the order: sodium > potassium > lithium tris(malonato) ferrate (III).
Thermal decomposition of lithium tris (malonato) ferrate (III) tetrahydrate i.e. Li3[Fe(CH2C2O4)3].4H2O has been studied in the temperature range of 353–873 K in static air atmosphere using Mössbauer, infrared spectroscopy and nonisothermal techniques (TG-DTG-DTA). The anhydrous complex decomposed into ferric oxide of varying particle sizes and alkali metal malonates/carbonates in succesive stages. Fimally a solid state reaction between -Fe2O3 and alkali metal carbonate gives fine particles of lithium ferrite (LiFeO2) at a temperature lower than for oxalate precursor and for ceramic method.
The thermal decomposition of sodium hexa-carboxylato/ferrates/III/ i.e. Na3[Fe/RCOO/6].xH2O /R=H, CH3, C2H5/ has been studied at various temperatures in air employing Mössbauer and infrared spectroscopies and non-isothermal techniques
/DTG, DTA, TG/. The thermolysis proceeds without undergoing the formation of any iron/II/ intermediate. The particle size
of α-Fe2O3 formed during thermolysis shows an increasing trend with increasing decomposition temperature. At higher temperatures α-NaFeO2 is formed as the ultimate product for all the complexes.