Room-temperature synthesis of monodisperse mixed spinel (CoxMn1–x)3O4 powder by a coprecipitation method
Abstract
Spinel oxide Co
3
O
4
has traditionally been synthesized by thermal decomposition of cobaltous salts at temperatures of 250-900°C under oxidizing conditions. Here, we report a solution synthesis route that yields mixed spinel oxide (Co
x
Mn
1–x
)
3
O
4
at room temperature in air. (Co
0.75
Mn
0.25
)
3
O
4
solid solutions were synthesized by coprecipitation and oxidation of Co(OH)
2
and Mn(OH)
2
from mixed aqueous solutions of Co- and Mn-salts. The spinel oxide phase was stabilized by crystallization of Mn
3
O
4
resulting from the oxidation of Mn(OH)
2
in the mother liquor. While undoped Mn
3
O
4
is tetragonal, the (Co
0.75
Mn
0.25
)
3
O
4
solid solution has a cubic symmetry due to the reduced Mn3+ concentration. The resulting powder is spherical with an average particle diameter of ca. 0.1 µm and a narrow size distribution. Transmission electron microscopy (TEM) showed that individual particles are nearly single crystalline but consist of a mosaic of multiple nanocrystallites. This observation supports an aggregation mechanism of formation for the nearly monodispersed particles.
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