Zusammenfassung
BaFe12-xTixO19 barium hexaferrites up to x = 2.00 were synthesized by
the usual ceramic technology. Crystal structure refinement was realized
by Rietveld method of powder XRD at room temperature. The unit cell
parameters change non-monotonically with titanium concentration. The minimum volume of -698.75 angstrom 3 was determined for the x = 1.00.
The mechanism of nonequivalent crystallographic positions occupation
with titanium cations is established. SEM investigation was shown that
the obtained samples are ceramics with a tightly compacted polycrystals
(>95%) and average crystallite size of -5 mu m. The Mo center dot
ssbauer investigation confirms such localization of Ti4+ cations. The
field dependence of magnetization at 5 K and 300 K was measured and the
main magnetic parameters were determined using the law of approach to
saturation. These values decrease almost monotonically with increase in
titanium concentration and temperature. The minimum values of these
quantities of -23.4 emu/g, -1.9 emu/g, 1.2*106 Erg/g and -105 Oe were fixed for the x = 2.00 at 300 K. With an increase in the doping
concentration, both the magnitude of the electrical ac-resistivity and
the temperature of transition to the activation type of conductivity increase non-monotonically. At x = 0.50, the lowest electrical
resistivity of rho -5.1*103 Ohm*cm is observed at room temperature
with the electrical transition temperature is Tel -406.5 K. With an
increase in frequency the ac-resistivity decreases, as the value of the
band gap. The real part of the permittivity increases constantly with
increasing temperature and decreases with increasing frequency for all
the compositions. The temperature peak of the tg(d) loss tangent with
the doping concentration changes nonmonotonically in magnitude and
position. An interpretation of the magnetic and electric states of the
substituted BaFe12-xTixO19 barium hexaferrite is given taking into
account the mechanism of occupation nonequivalent crystallographic
positions with titanium cations.
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