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The effect of the thermal decomposition reaction on the mechanical and magnetocaloric properties of La(Fe,Si,Co)13

Löwe, Konrad and Liu, Jian and Skokov, Konstantin and Moore, James D. and Sepehri-Amin, Hossein and Hono, Kazuhiro and Katter, Matthias and Gutfleisch, Oliver (2012):
The effect of the thermal decomposition reaction on the mechanical and magnetocaloric properties of La(Fe,Si,Co)13.
In: Acta Materialia, Elsevier Science Publishing, pp. 4268-4276, 60, (10), ISSN 13596454,
[Online-Edition: http://dx.doi.org/10.1016/j.actamat.2012.04.027],
[Article]

Abstract

We report on the influence of the Co content in the magnetocaloric system La(Fe,Si,Co)13 on the thermal decomposition (TD) reaction, and subsequently on the magnetocaloric properties. In the course of the TD reaction, the magnetocaloric La(Fe,Si,Co)13 phase reversibly decomposes into α-Fe(Co,Si) and the intermetallic LaFeSi phase, thus enhancing the mechanical properties and therefore the machinability of the compound. The addition of Co significantly speeds up the reaction kinetics. The optimum temperature range for the TD reaction was determined to be 973–1073 K, with the lower and upper limit at 873 K and 1173 K, respectively. With electron microscopy a lamellar microstructure has been found in the decomposed state, indicating a eutectoid-type phase reaction. The width of the lamellae is ∼26 nm in LaFe12Si and decreases with increasing Co content. Three-dimensional atom probe (3DAP) measurements show the enrichment of Co and Si in LaFeSi lamellae. We conclude that the addition of Co somehow decreases the lamellar spacing, which is the main reason for the enhanced TD kinetics. Finally, it is interesting to note that the highly ordered nano-scale mixture of strongly ferromagnetic α-Fe(Co) with the non-ferromagnetic phase induces a significant increase in coercivity, Hc. The shape anisotropy of the thin α-Fe(Co) lamellae yields a semi-hard permanent magnet with a coercivity of ∼100 A cm−1.

Item Type: Article
Erschienen: 2012
Creators: Löwe, Konrad and Liu, Jian and Skokov, Konstantin and Moore, James D. and Sepehri-Amin, Hossein and Hono, Kazuhiro and Katter, Matthias and Gutfleisch, Oliver
Title: The effect of the thermal decomposition reaction on the mechanical and magnetocaloric properties of La(Fe,Si,Co)13
Language: English
Abstract:

We report on the influence of the Co content in the magnetocaloric system La(Fe,Si,Co)13 on the thermal decomposition (TD) reaction, and subsequently on the magnetocaloric properties. In the course of the TD reaction, the magnetocaloric La(Fe,Si,Co)13 phase reversibly decomposes into α-Fe(Co,Si) and the intermetallic LaFeSi phase, thus enhancing the mechanical properties and therefore the machinability of the compound. The addition of Co significantly speeds up the reaction kinetics. The optimum temperature range for the TD reaction was determined to be 973–1073 K, with the lower and upper limit at 873 K and 1173 K, respectively. With electron microscopy a lamellar microstructure has been found in the decomposed state, indicating a eutectoid-type phase reaction. The width of the lamellae is ∼26 nm in LaFe12Si and decreases with increasing Co content. Three-dimensional atom probe (3DAP) measurements show the enrichment of Co and Si in LaFeSi lamellae. We conclude that the addition of Co somehow decreases the lamellar spacing, which is the main reason for the enhanced TD kinetics. Finally, it is interesting to note that the highly ordered nano-scale mixture of strongly ferromagnetic α-Fe(Co) with the non-ferromagnetic phase induces a significant increase in coercivity, Hc. The shape anisotropy of the thin α-Fe(Co) lamellae yields a semi-hard permanent magnet with a coercivity of ∼100 A cm−1.

Journal or Publication Title: Acta Materialia
Volume: 60
Number: 10
Publisher: Elsevier Science Publishing
Uncontrolled Keywords: Magnetocaloric, La(Fe,Si)13, Thermal decomposition, Ageing, Microstructure
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Functional Materials
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 19 Apr 2013 11:28
Official URL: http://dx.doi.org/10.1016/j.actamat.2012.04.027
Identification Number: doi:10.1016/j.actamat.2012.04.027
Funders: The research leading to these results has received funding from the European Community’s 7th Framework Programme under Grant Agreement No. 214864 (SSEEC).
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