ISSN 10637397, Russian Microelectronics, 2015, Vol. 44, No. 8, pp. 517–522. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © I.I. Kaneva, V.G. Kostishin, V.G. Andreev, D.N. Chitanov, A.N. Nikolaev, E.I. Kislyakova, 2014, published in Izvestiya Vysshikh Uchebnykh Zavedenii.
Materialy Elektronnoi Tekhniki, 2014, No. 3, pp. 183–188.
Hexaferrites have a magnetoplumbitetype hexag
onal crystal structure , one easy magnetic axis, and
a high constant of magnetic anisotropy:
—for barium hexaferrite,
—for strontium hexaferrite,
This allows one to use hexaferrites for fabricating
constant magnets with high coercivity.
Ferrite magnets are also characterized by the possi
bility of multipolar magnetization on a onepiece
compact product and by low electrical conductivity,
which makes it possible to use ferrite magnets in the
presence of highfrequency magnetic fields. By com
bining corrosionresistant powders of ferrite magnets
with polymer binders and by using extrusion or rolling
techniques, one can fabricate flexible and elastic prod
ucts in the form of bands or thin films . The disad
vantage of ferrite magnets is that coercivity depends
heavily on temperature, which limits the application of
these materials at negative temperatures (below –20°C).
The properties of constant powder magnets depend on
the technological methods of their production, where
production modes can be varied at any manufacturing
Anisotropic hexaferrites, which are pressed in the
magnetic field, have the best magnetic properties. Iso
tropic barium hexaferrites, however, are also widely
used in practice . Because of the flaky structure of
barium hexaferrite particles, even when pressing is
performed without the magnetic field, the texture in
the sample is formed, which results in the deteriora
tion of the properties of isotropic hexaferrites.
When the standard ceramic processing technology
is used to obtain isotropic hexaferrites [8–10], flaky
hexaferrite particles are formed from a mixture of the
initial components in the process of diffusion anneal
ing. On the further pressing of granulated hexaferrite
particles, despite the absence of the magnetic field, the
undesired texture is formed in the pressed samples.
When sintering raw samples, the texture is consider
Obtaining Barium Hexaferrite Brand 7BI215
with Improved Isotropic Properties
I. I. Kaneva
, V. G.
, V. G.
, D. N.
, and E. I.
National University of Science and Technology (MISiS), Leninskii pr. 4, Moscow, 119049 Russia
Kuznetsk Institute of Informatics and Management Technologies (Branch of Penza State University),
ul. Mayakovskogo 57a, Kuznetsk, 442600 Russia
email: email@example.com, firstname.lastname@example.org
Received December 3, 2014
—Currently, the global production of permanent magnets is about 150000 tons per annum, in which
the share of ceramic magnets made of barium and strontium hexaferrites is more than 90%.
hexaferrites have outstanding magnetic properties; in these materials, the texture is formed by pressing in the
magnetic field, i.e., the hexagonal axes of flaky powder particles are oriented in the direction of the magnetic
field; thus, the magnetic properties in this direction increase and decrease in the other directions. However,
in a great number of applications, cheaper isotropic magnets, which have inferior magnetic properties, are
successfully used; in these magnets, the magnetic axes of the particles are distributed uniformly in all direc
tions, so magnetic properties are the same in all directions. The wellknown technologies for fabricating iso
tropic magnets do not provide sufficient isotropy of magnetic properties, since the texture, which is due to the
orientation of flaky hexaferrite particles, is formed in the process of pressing, which, in turn, reduces the mag
netic energy of ring magnets in the radial direction. In this paper, we investigate the possibility of obtaining
barium hexaferrite with isotropic properties by using a short manufacturing scheme, which includes no oper
ations of diffusion annealing and grinding. It is shown that such a manufacturing scheme, which involves
pressing the mixture (granulated with a binder) of the initial components with the nearspherical shape of
particles, makes it possible to improve the isotropic properties of the magnet.
: barium hexaferrite, strontium hexaferrite, microstructure, grinding, isotropic and anisotropic