Optimum conditions for the preparation of tape recording quality γ-Fe₂O₃ by the thermal decomposition of ferrous oxalate dihydrate have been established. Formation of the intermediate Fe₃O₄ which is most important in forming γ-Fe₂O₃ takes place only in the presence of water vapour. Various stages of decomposition have been characterised by DTA, TG, DTG, and x-ray powder diffraction. The method for the preparation of acicular γ-Fe₂O₃ that matches very well with the commercial tape recording material has been developed.

Acicular FeC₂O₄ · 2H₂O was precipitated from glycerol and starch media. Thermal decomposition of this oxalate in dry and moist nitrogen yielded primarily FeO and Fe₃O₄ respectively. Characterization was attempted through DTA, TG, x-ray diffraction, TEM and magnetization studies. It was found that the oxalate can be completely decomposed to Fe₃O₄ in moist nitrogen (P_H2O ∼ 35 torr) at 775 K and then oxidised by dry air to acicular γ-Fe₂O₃ at 575 K. The resulting material has saturation magnetization (∼ 70 emu/g), coercive field (∼ 300 Oe) and squareness ratio (∼ 0·60–0·65), which values art comparable with those of the commercial samples.

Optimum conditions and experimental details for the formation of γ-Fe₂O₃ from goethite have been worked out. In another method, a cheap complexing medium of starch was employed for precipitating acicular ferrous oxalate, which on decomposition in nitrogen and subsequent oxidation yielded acicular γ-Fe₂O₃. On the basis of thermal decomposition in dry and moist nitrogen,dta, xrd, gc and thermodynamic arguments, the mechanism of decomposition was elucidated. New materials obtained by doping γ-Fe₂O₃ with 1–16 atomic percent magnesiu, cobalt, nickel and copper, were synthesised and characterized.

Magnetic materials meant for audio/video recording applications necessitate that polycrystalline materials be in acicular shape. So preparation of acicular precursors for magnetic storage materials assumes significance. The employment of aqueous solutions do not produce needle shape crystallites. Glycerol is one of the complexing media used for the precipitation of ferrous oxalate dihydrate. An inexpensive method using starch for preparation of acicular particles is described. The influence of an additive namely Gd on acicularity is also investigated.

Compounds belonging to the series PbSb$_x$Te$_{1-x}$ and Pb$_{1-x}$Sb$_x$Te ($x = 0.1, 0.3, 0.5$) were prepared in thenanostructured form by employing high-energy ball-milling and subsequent hot-pressing. The amphoteric property of antimony was utilized to substitute lead and tellurium in the compounds having the formula PbSb$_x$Te$_{1-x}$ and Pb$_{1-x}$Sb$_x$Te to make them p and n. All the compositions were evaluated for their figure of merit (ZT) and power factor afterascertaining their Seebeck coefficient, electrical and thermal conductivities. These compositions exhibited very high Seebeck coefficient both in low- and room-temperature regimes. Thermoelectric generator modules were constructed using combinations of n- and p-type PbSbTe and the voltage developed was measured and compared with the calculatedvalues, and they are found to be in good agreement. Different combinations of p- and n-types from the series were tested,and the best among them were identified.