D K Chakrabarty
Articles written in Bulletin of Materials Science
Volume 2 Issue 4 November 1980 pp 239-249 Communications
Ferroelectric ceramics of the general formula
Volume 3 Issue 1 February 1981 pp 1-8
Some new potential dielectric materials have been made through the cross-substitution of Ba2+ by a 1:1 molar combinations of tri-(La3+) and mono-valent (Li+, Na+, K+) ions at the Ba2+ site in BaTiO3. Chemical analysis shows that compositions in the potassium series are about 6·1% deficient in their K2O content and exhibit interesting dielectric relaxations. The cross-substitution has lowered the
Volume 3 Issue 2 July 1981 pp 201-208 Biswas Memorial Symposium On The Chemistry And Physics of Solids, Magnetism And Magnetic Properties Of Materials
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.
Volume 3 Issue 3 November 1981 pp 275-280
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 (PH2O ∼ 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.
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