80
L. A. Frolova et al.
concentration of constituent components. This is unacceptable for ferrites, the
properties of which are very sensitive to residual chemical in homogeneities. All
this encourages the search for methods of synthesis, different from classical ceramic
technology, and, accordingly, the study of the crystal-chemical structure and the
analysis of the physicochemical characteristics of cobalt ferrites.
A lot of research has been devoted to the formation of the spinel structure. The
solid-phase technologies for the production of cobalt ferrites were considered in
detail in works [6, 7], the concentration dependences of the crystal lattice parameter
and the magnetic saturation moment in the region of spinel solid solutions of ´Ñ 3 ± 4
with Fe 3 O 4 were described in [8, 9], and the results of studying the formation
boundaries of single-phase solid solutions in the ´Ñ±-Fe 2 O 3 system were analyzed
in [10]. The authors [11–13] studied the conditions for the formation of cobaltdoped magnetite with a spinel structure in the course of solid-phase synthesis. The
structure and properties of the samples were also studied.
To achieve high homogeneity of nanodispersed-size particles of the synthesized
product, chemical methods of production were used (sol-gel method [14], autoignition [15, 16], hydrothermal [17], and coprecipitation methods [18]). For example,
in the work [19], ferrite was obtained with the hydrothermal method, which made
possible to achieve/produce uniform sphere-shaped nanopowder sand to increase
the magnetic properties as compared to systems synthesized by the traditional
precipitation method.
The peculiarity of hydrophase synthesis lies in the fact that all the reagents
are mixed at the atomic or molecular level, which ensures high stoichiometry and
homogeneity of the distribution of the final product particles both in size and from
a chemical point of view. No less important advantage of chemical methods of
production is their high efficiency (much lower synthesis temperatures are used
compared to the solid phase) and relatively simple and affordable equipment.
The properties of plasma treatment were used for the synthesis of complex
inorganic compounds [20–22]. The synthesis of ferrites by CNP was considered
in this work [23]. The authors [24] carried out a study of the crystal-chemical properties of cobalt ferrite compositions under plasma spraying. The paper described
the mechanism of the action of low-pressure plasma with a liquid cathode on
various salt solutions [25]. The authors introduced the technology of obtaining
ferrite nanoparticles by an electrochemical method [26]. The work [15] studied
the influence Cr 3+ concentrations of the initial solution on the properties of cobalt
ferrite obtained from the citrate solution. There are not enough works devoted to
the investigation of the CNP influence on the formation of cobalt ferrites. The
possibility of this synthesis was shown in the work [27].
In this paper, we presented the results of further studies in this direction.
The aim of the study was to determine the crystal-chemical parameters of cobalt
ferrites with a spinel structure in the Co x Fe 3-x O 4 system (0.25 ≤ x ≤1) as well
as to establish the dependence of the structure and magnetic characteristics of the
resulting compounds.
L. A. Frolova et al.
concentration of constituent components. This is unacceptable for ferrites, the
properties of which are very sensitive to residual chemical in homogeneities. All
this encourages the search for methods of synthesis, different from classical ceramic
technology, and, accordingly, the study of the crystal-chemical structure and the
analysis of the physicochemical characteristics of cobalt ferrites.
A lot of research has been devoted to the formation of the spinel structure. The
solid-phase technologies for the production of cobalt ferrites were considered in
detail in works [6, 7], the concentration dependences of the crystal lattice parameter
and the magnetic saturation moment in the region of spinel solid solutions of ´Ñ 3 ± 4
with Fe 3 O 4 were described in [8, 9], and the results of studying the formation
boundaries of single-phase solid solutions in the ´Ñ±-Fe 2 O 3 system were analyzed
in [10]. The authors [11–13] studied the conditions for the formation of cobaltdoped magnetite with a spinel structure in the course of solid-phase synthesis. The
structure and properties of the samples were also studied.
To achieve high homogeneity of nanodispersed-size particles of the synthesized
product, chemical methods of production were used (sol-gel method [14], autoignition [15, 16], hydrothermal [17], and coprecipitation methods [18]). For example,
in the work [19], ferrite was obtained with the hydrothermal method, which made
possible to achieve/produce uniform sphere-shaped nanopowder sand to increase
the magnetic properties as compared to systems synthesized by the traditional
precipitation method.
The peculiarity of hydrophase synthesis lies in the fact that all the reagents
are mixed at the atomic or molecular level, which ensures high stoichiometry and
homogeneity of the distribution of the final product particles both in size and from
a chemical point of view. No less important advantage of chemical methods of
production is their high efficiency (much lower synthesis temperatures are used
compared to the solid phase) and relatively simple and affordable equipment.
The properties of plasma treatment were used for the synthesis of complex
inorganic compounds [20–22]. The synthesis of ferrites by CNP was considered
in this work [23]. The authors [24] carried out a study of the crystal-chemical properties of cobalt ferrite compositions under plasma spraying. The paper described
the mechanism of the action of low-pressure plasma with a liquid cathode on
various salt solutions [25]. The authors introduced the technology of obtaining
ferrite nanoparticles by an electrochemical method [26]. The work [15] studied
the influence Cr 3+ concentrations of the initial solution on the properties of cobalt
ferrite obtained from the citrate solution. There are not enough works devoted to
the investigation of the CNP influence on the formation of cobalt ferrites. The
possibility of this synthesis was shown in the work [27].
In this paper, we presented the results of further studies in this direction.
The aim of the study was to determine the crystal-chemical parameters of cobalt
ferrites with a spinel structure in the Co x Fe 3-x O 4 system (0.25 ≤ x ≤1) as well
as to establish the dependence of the structure and magnetic characteristics of the
resulting compounds.