Hydrothermal synthesis of homogeneous and core/shell CoxNi1−xFe2O4 nanoparticles

The hydrothermal synthesis (HS) of homogeneous and core shell Co
_x
Ni
_1-x
Fe
₂
O
₄
nanoparticles (NPs) from mixed FeCl
₃
/ CoCl
₂
/ NiCl
₂
precursor solutions has been investigated, using the complementary characterization techniques of X-ray diffractometry, transmission electron microscopy, energy dispersive X-ray analysis and electron energy loss spectroscopy. At pH ~ 8, the HS of Co
_x
Ni
_1-x
Fe
₂
O
₄
NPs, up to ~ 25 nm in size, was found to proceed through the formation and dissolution of intermediate Fe(OH)
₃
and [FeCoNi
₂
(OH)
₈
]
⁺
.[Cl.H
₂
O]
^-
phases. The structure of core/shell NiFe
₂
O
₄
/CoFe
₂
O
₄
and CoFe
₂
O
₄
/NiFe
₂
O
₄
NPs were confirmed.