Sol-gel auto-combustion synthesis of Ba�Sr hexaferrite ceramic powders

Shariff, YKR and Choudhary, HK and Khopkar, V and Yadav, A and Madhusudhana, R and Sahoo, B (2020) Sol-gel auto-combustion synthesis of Ba�Sr hexaferrite ceramic powders. In: Ceramics International . (In Press)

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Abstract

We report the mechanism involved in sol-gel auto-combustion synthesis of Ba�Sr-hexaferrite (Ba1-xSrxFe12O19; x = 0, 0.25, 0.5, 0.75 and 1, BSFO) ceramic powders through the analysis of the phases evolved during annealing of the as-synthesized powders, along with their structure and morphological studies. The XRD patterns of the as-synthesized samples indicate the formation of barium/strontium monoferrite ((Ba/Sr)Fe2O4) and maghemite (γ-Fe2O3) phases along with a minute amount of hematite (α-Fe2O3) phase. Annealing of these samples facilitates formation of BSFO phase through the solid state reaction between BaFe2O4 and γ-Fe2O3 phase. Interestingly, after annealing the samples with x = 0, 0.5 and 1, at 1000 °C for 2 h, we observed that phase pure Ba�Sr hexaferrite structure forms, but for samples with x = 0.25 and 0.75, high amount of hematite (α-Fe2O3) phase is observed, especially for x = 0.75. The reason associated with this could be the large difference between the ionic radii of Ba2+ and Sr2+ ions occupying the oxygen site. Furthermore, our study on annealing dependent phase evolution confirms that, this difference in ionic radii forbids the formation of a single phase Ba�Sr hexaferrite. The growth of clear hexagonal-shaped plate-like particles with varied particle sizes was observed for all the samples. The particle size variation may be due to the influence of the ionic radii difference on the sinterability of the samples. Our study provides a better understanding of synthesis mechanism of Ba�Sr hexaferrite samples. © 2020 Elsevier Ltd and Techna Group S.r.l.

Item Type:	Journal Article
Publication:	Ceramics International
Publisher:	Elsevier Ltd
Additional Information:	Copy right for this article belongs to Elsevier Ltd
Keywords:	Annealing; Barium metallography; Combustion synthesis; Ferrite; Hematite; Particle size; Particle size analysis; Powders; Sol-gel process; Sol-gels; Solid state reactions, As-synthesized powder; Morphological study; Particle size variation; Phase evolutions; Sol-gel auto-combustion; Sr hexaferrite; Structure forms; Synthesis mechanism, Barium compounds
Department/Centre:	Division of Chemical Sciences > Materials Research Centre
Date Deposited:	13 Nov 2020 11:07
Last Modified:	13 Nov 2020 11:07
URI:	http://eprints.iisc.ac.in/id/eprint/66118

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