Mn-substituted M-type Sr-hexaferrites, SrFe12-xMnxO19 (x = 0, 2, 4, 6, 8, 10, 12) were prepared using the sol-gel and post-annealing processes. XRD analysis on x = 0 sample revealed that the crystalline M-type hexaferrite phase can be formed at the post-annealing temperature, T-ann >= 700 degrees C. The sol-gel processed powders of SrFe12-.xMnxO19 (x = 0, 2, 4, 6, 8, 10, 12) annealed a t 900 degrees C were ground, pressed into pellets, and sintered in air at 1100 and 1200 degrees C for 4 h, respectively. Single M-type hexaferrite phase is formed in samples of x <= 8 sintered at 1100 degrees C, while it is found in the samples of x <= 6 sintered at 1200 degrees C. Scanning electron microscope (SEM) was used for the study of microstructure. For the samples sintered at 1100 degrees C, as increase of x from 0 to 6, the resistivity significantly decreases from 1.8 x 10(8) Omega.cm to 5.5 x 10(3) Omega.cm, the saturation magnetization value decreases and the coercivity increases. Complex permittivity and permeability were measured on the toroidal shaped samples of SrFe12-xMnxO19 (x = 0, 2, 4, 6, 8)-epoxy (10 wt%) composites. The effects of Mn substitution on the electrical and magnetic, and high frequency properties of the M-type Sr-hexaferrites are discussed.
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