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

M-type strontium ferrites with the substitution of Sr(2+) by La(3+) were prepared by a sot-gel process. The crystalline structure, sublattice structure and microwave absorption properties of Sr(1-x)La(x)Fe(12)O(19) (x = 0.05, 0.1, 0.15, 0.2) were studied by X-ray diffraction. Mossbauer spectroscopy and vector network analyzer. The results showed that the single lattice structure of strontium ferrite can be obtained when the substitution amount x < 0.15, with some Fe(3+) changes to Fe(2+) on 2a site. The minimum reflection loss of the substituted ferrite (x=0.15) reaches -41.7dB with the -10dB bandwidth over 4GHz at the thickness of 2.3 mm. The microwave absorption performance was remarkably improved due to the grain dimension reduction and the valence change of Fe ions induced by the substitution of lanthanum. (C) 2009 Elsevier B.V. All rights reserved.