| Summary: | W-type hexaferrites were discovered in the 1950s and are of interest for their potential applications. In this context, many researchers have conducted studies on the partial substitution of Fe sites in order to modify their electric and magnetic properties. In this study, W-type SrYb hexaferrites using Al<sup>3+</sup> as substitutes for Fe<sup>3+</sup> sites with the nominal composition Sr<sub>0.85</sub>Yb<sub>0.15</sub>Zn<sub>1.5</sub>Co<sub>0.5</sub>Al<sub>x</sub>Fe<sub>16−x</sub>O<sub>27</sub> (0.00 ≤ x ≤ 1.25) were successfully synthesized via the two-step calcination method. The microstructures, spectral bands of characteristic functional groups, morphologies, and magnetic parameters of the prepared samples were characterized using XRD, FTIR, SEM, EDX, and VSM. The XRD results showed that, compared with the standard patterns for the W-type hexaferrite, the W-type SrYb hexaferrites with the Al content (x) of 0.00 ≤ x ≤ 1.25 were a single-W-type hexaferrite phase. SEM images showed the flakes and hexagonal grains of W-type hexaferrites with various Al content (x). The saturation magnetization (<i>M</i><sub>s</sub>) and magneton number (<i>n<sub>B</sub></i>) decreased with Al content (x) from 0.00 to 1.25. The remanent magnetization (<i>M</i><sub>r</sub>) and coercivity (<i>H</i><sub>c</sub>) decreased with Al content (x) from 0.00 to 0.25. Additionally, when the Al content (x) ≥ 0.25, <i>M</i><sub>r</sub> and <i>H</i><sub>c</sub> increased with the increase in the Al content (x). The magnetic anisotropy field (<i>H</i><sub>a</sub>) and first anisotropy constant (<i>K</i><sub>1</sub>) increased with the Al content (x) increasing from 0.00 to 1.25. Al-substituted W-type SrYb hexaferrites with soft magnetic behavior, high <i>M</i><sub>s</sub>, and lower <i>H</i><sub>c</sub> may be used as microwave-absorbing materials.
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