Effect of aluminum substitution on microwave absorption properties of barium hexaferrite

Abstract

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 BaFe12−xAlxO19 (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 Al3+ ions enter into the lattice of hexagonal barium ferrite. The substitution of Al3+ 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 Al3+ ions preferentially occupy the 4f2, 2a, 4f1, and 12k sites in the subcrystalline structure up to x=1.9, and then the Al3+ ions mainly occupy 12k sites. This change also results in 2b sites with a large quadrupole splitting. These occupations lead to a variable magnetocrystalline anisotropy field.

Structural and magnetic behavior of Pr-substituted M-type hexagonal ferrites synthesized by sol–gel autocombustion for a variety of applications

“…1 reflects the TGA/DTA graphs of the sample with composition Ba 0.25 Sr 0.75 Pr 0.2 Fe 11.8 O 19 . The thermal analysis shows the mechanism for the formation of hexaferrite phase.…”

“…An attempt has been made here to evaluate the effect of small addition of rare earth element Praseodymium (Pr) on the structural and magnetic properties of Sr-Ba based hexaferrites. To the best of our knowledge, Pr-substituted hexaferrites with chemical formula Ba 0.25 Sr 0.75 Pr x Fe 12À x O 19 have not been investigated previously. Therefore, the main focus of this study was to synthesize these materials by a low cast and simpler method and to investigate their structural and magnetic properties which may be suitable for different applications such as magnetic recording media and microwave devices etc.…”

Hopkinson peak and superparamagnetic effects in BaFe12-xGaxO19nanoparticles

“…These materials have been investigated due to their importance for both fundamental research and technological applications in permanent magnets, high-density magnetic recording, magneto-optics and microwave devices [1][2][3][4][5][6]. Different techniques have been used to prepare and characterize hexaferrite particles [7][8][9][10][11][12][13].…”

Microwave absorption properties of La-substituted M-type strontium ferrites

“…The researchers have extensively studied the influence of partial Fe 3+ substitution by divalent-tetravalent ions (such as Co 2+ -Si 4+ [13], Co 2+ -Ti 4+ [14], Mg 2+ -Ti 4+ [15], Ni 2+ -Ti 4+ [16], Mn 2+ -Co 2+ -Zr 4+ [17], Co 2+ -Ru 4+ [18] etc.) and trivalent metal ions (such as Al 3+ [19], Cr 3+ [20], Ga 3+ [21], In 3+ [22] etc.) on the microwave properties of M-type hexagonal ferrites.…”