Synthesis, structure and properties of a semivalent iron oxoborate, Fe2OBO3
Abstract
Transition metal oxoborates are of interest for magnetic and optical properties. Crystals of many M
II
2
M
III
O
2
BO
3
and M
II
M
III
OBO
3
materials can be grown from borate fluxes. In the Fe
II
-Fe
III
-B-O system, flux growth results in Fe
3
O
2
BO
3
crystals, but solid state reaction at higher temperatures has yielded Fe
2
OBO
3
as a polycrystalline powder. This has been characterised by synchrotron and neutron diffraction, electron microscopy, Mössbauer spectroscopy, and conductivity and magnetic measurements. Two notable transitions occur, a broad semiconductor-semiconductor change accompanied by a structural transition at 317 K, and L-type ferrimagnetic order below a Curie temperature of 155 K. An average (Fe
2+
)
0.5
(Fe
3+
)
0.5
valence is observed at the two crystallographically distinct sites in Fe
2
OBO
3
, indicating that charge ordering occurs.
- This article is part of the themed collection: Solid state chemistry: Novel Syntheses and New Materials: Materials Discussion 1
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