Cobalt ferrite powders were synthesized by solid state reaction of the nanosized oxides at different temperatures. The highly aggregated powders were milled, and the aggregate size was reduced from 25 – 40 μm to 12–20 μm, depending on the milling time. A correlation between milling media diameter and final granulometry, and an unexpected calcination temperature effect on the milling efficiency were found. Highly homogenous green bodies and fully dense materials were produced for the first time after conventional sintering. The crystallite size depends primarily on the heating conditions and decreases from 50 – 70 nm to 27–13 nm. Under the same sintering conditions, particle morphology and crystallite size control the final grain shape, producing twinned grains with increased multiple parallel twinning overgrowth for the finer powders. The sintered cobalt ferrite ceramics show a relative density of 96–99%. The higher the planar faults density and grain size, the lower is the induced magnetization due to increased domain walls pinning. The variation of initial susceptibility was explained by extending the Globus model to the case where the domain walls are pinned at twinning boundaries. A linear correlation between multiparallel-twinned grains fraction and initial susceptibility was found.

Multiple parallel twinning overgrowth in nanostructured dense cobalt ferrite / Galizia, Pietro; Baldisserri, Carlo; Capiani, Claudio; Galassi, Carmen. - In: MATERIALS & DESIGN. - ISSN 0264-1275. - 109:(2016), pp. 19-26. [10.1016/j.matdes.2016.07.050]

Multiple parallel twinning overgrowth in nanostructured dense cobalt ferrite

GALIZIA, PIETRO;
2016

Abstract

Cobalt ferrite powders were synthesized by solid state reaction of the nanosized oxides at different temperatures. The highly aggregated powders were milled, and the aggregate size was reduced from 25 – 40 μm to 12–20 μm, depending on the milling time. A correlation between milling media diameter and final granulometry, and an unexpected calcination temperature effect on the milling efficiency were found. Highly homogenous green bodies and fully dense materials were produced for the first time after conventional sintering. The crystallite size depends primarily on the heating conditions and decreases from 50 – 70 nm to 27–13 nm. Under the same sintering conditions, particle morphology and crystallite size control the final grain shape, producing twinned grains with increased multiple parallel twinning overgrowth for the finer powders. The sintered cobalt ferrite ceramics show a relative density of 96–99%. The higher the planar faults density and grain size, the lower is the induced magnetization due to increased domain walls pinning. The variation of initial susceptibility was explained by extending the Globus model to the case where the domain walls are pinned at twinning boundaries. A linear correlation between multiparallel-twinned grains fraction and initial susceptibility was found.
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

Caricamento pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11583/2645329
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo