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Abstract

In the present work, the conventional method of increasing the efficiency of solid-phase synthesis of lithium–zinc ferrites that involves multiple intermediate grinding of briquetted reaction mixtures annealed at high temperatures is compared with a new radiation-thermal (RT) method using a high-power pulsed beam of accelerated electrons for heating of reaction mixtures. An analysis of the TG(M)/DTG(M) curves recorded in a magnetic field demonstrates that the efficiency of Li0.3Zn0.4Fe2.3O4 synthesis from Li2CO3–Fe2O3–ZnO mechanical mixture at a temperature of 700 °C during 120 min is equivalent to thermal annealing at 800 °C, but with the triple annealing duration.

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Abstract  

The objective of present research was to sinter nanosized Mn–Zn ferrites (MZF) at low temperature (≤1,000 °C) by avoiding the formation of nonmagnetic phase (hematite). For this purpose, MZF powder was synthesized by sol–gel auto combustion process at 220 °C and further calcined at 450 °C. In calcined powder, single phase (spinel) was confirmed by X-ray diffraction analysis. Pellets were pressed, having 43% of the theoretical density and showing 47 emu gm−1 saturation magnetization (M s). Various combinations of heating rate, dwelling time and gaseous environment were employed to meet optimum sintering conditions at low temperature (≤1,000 °C). It was observed that sintering under air or N2 alone had failed to prevent the formation of nonmagnetic (hematite) phase. However, hematite phase can be suppressed by retaining the green compacts at 1,000 °C for 180 min in air then further kept for 120 min in nitrogen. Under these conditions, spinel phase (comprising of nano crystallites), 90% of theoretical density and 102 emu gm−1 of saturation magnetization has been achieved.

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Abstract  

Control of processing parameters, in both conventional ceramic routes and novel gel processing routes, is vital in the production of electronic and magnetic ceramics. The role of thermal analysis in the provision of basic data for the understanding of both types of processing route is discussed with special emphasis being placed upon the production of 1–2–3 YBCO superconductors and MgO-based soft ferrite materials for TV deflection unit applications.

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, Lysenko EN , Vasendina EA , Sokolovskii AN , Vlasov VA , Pritulov AM . Thermogravimetric investigation of the effect of annealing conditions on the soft ferrite phase homogeneity . J Therm Anal Calorim . 2010 [Online First

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, Vlasov , VA , Pritulov , AM . 2011 . Thermogravimetric investigation of the effect of annealing conditions on the soft ferrite phase homogeneity . J Therm Anal Calorim . 104 : 613 – 617 10.1007/s10973-010-1074-4 . 12

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