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Effect of aluminum substitution on microwave absorption propertiesof barium hexaferrite
Ist Teil von
Journal of applied physics, 2005-11, Vol.98 (10), p.103905-103905-5
Ort / Verlag
American Institute of Physics
Erscheinungsjahr
2005
Link zum Volltext
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
Aluminum substituted barium hexaferrites were prepared by the self-propagating combustion method and subsequent calcination at 850°C. The crystalline structure, complex permittivity, complex permeability, and hyperfine parameters of
BaFe
12
−
x
Al
x
O
19
(
x
varies from 1.5 to 2.3 in steps of 0.2) were measured with x-ray diffraction (XRD), vector network analyzer and Mössbauer spectroscopy. The XRD results show that all
Al
3
+
ions enter into the lattice of hexagonal barium ferrite. The substitution of
Al
3
+
ions can greatly affect the complex permittivity and permeability of barium ferrite. With increasing substitution, the real part of complex permittivity increases gradually, and the peaks of the imaginary part of complex permeability shift into higher frequency band. When the substitution amount
x
is 1.9, the largest movement of the peaks is 1.95 GHz, which indicates that the ferromagnetic resonant frequency of barium ferrite increases by 1.95 GHz. The
Al
3
+
ions preferentially occupy the
4
f
2
,
2
a
,
4
f
1
, and
12
k
sites in the subcrystalline structure up to
x
=
1.9
, and then the
Al
3
+
ions mainly occupy
12
k
sites. This change also results in
2
b
sites with a large quadrupole splitting. These occupations lead to a variable magnetocrystalline anisotropy field.