Self propagating high temperature synthesis of BaFe12–xCrxO19 and Li0.5Fe2.5–xCrxO4
Abstract
Thermal initiation of a mix of BaO
2
, Fe
2
O
3
, Cr
2
O
3
and iron powder in air induces a self propagating reaction with velocity 1-2 mm s
–1
and the formation of predominantly BaFe
12–x
Cr
x
O
19
. Thermal initiation of a mixture of Li
2
O
2
, Fe
2
O
3
, Cr
2
O
3
and iron powder in air also induces a propagation wave with formation of predominantly Li
0.5
Fe
2.5–x
Cr
x
O4. Heating either product mixture to 1150-1200 °C for 2 h produces phase pure crystalline powders of BaFe
12–x
Cr
x
O
19
and Li
0.5
Fe
2.5–x
Cr
x
O
4
. An external 1.1 T magnetic field increased the SHS synthesis wave velocity and temperature for both hard (BaFe
12–x
Cr
x
O
19
) and soft ferrites (Li
0.5
Fe
2.5–x
Cr
x
O
4
). Materials synthesised in a magnetic field showed significant changes in H
c
, σ
max
and σ
r
compared to those synthesized in zero field. All the samples were characterised by X-ray powder diffraction, FTIR, VSM, EDAX/SEM and Mössbauer spectroscopy.
- This article is part of the themed collection: Solid state chemistry: Novel Syntheses and New Materials: Materials Discussion 1
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